dSLR Sensor Cleaning

Background

You've been taking great shots with your dSLR for some time, changing lenses for the occasion, and now you notice some spots in your photos in bright areas like blue skies.  The spots seem to be in the same place in the frame with each shot.  Then a sinking feeling of doom ensues as you realize you have dust in the camera and visions of opening the camera and electronic microsurgery enter your mind.  Sensor cleaning can seem beyond the ability of the average dSLR owner but the procedure really isn't very difficult.  It all comes down to your ability to follow instructions in most cases.  Let's take a look at sensor dust and sensor cleaning to see if it is something you would like to try or if you'd rather take the camera to your local camera shop instead.

Recognizing dust and debris

Above are two examples of dust in the camera.  Dust can appear as near-pinpoint specs (top crop) or more diffuse/larger circles (bottom crop).  The above is a relatively mild case of dust and you may see other types of debris such as much larger or darker spots, small hairs, and so on.  Dust is more visible in areas of bright, uniform color such as blue skies.  In addition, due to the angle of light and the shadow created on the sensor by the dust, the dust often appears more diffuse at larger apertures and closer to small specs at small apertures.  Most importantly, the specs or circles will be in the same place in each frame.

If you see spots like those above in your photos and suspect dust in the camera, the first logical step is to go to an environment that is relatively dust free, remove the lens, and carefully clean both the front and rear glass elements on the lens.  If spots still appear after cleaning the lens, you'll know the dust is on the sensor.  Next, set your camera to aperture priority and select a very small aperture like f/22.  Set the camera to the lowest ISO setting such as ISO 100.  Now find a uniform surface like a white ceiling or wall in a well lit room.  It is more important that the surface be as uniform and texture-free as possible than the surface being white: any light color will do.  Take a shot of the wall/ceiling.  Note that if the camera picks an exposure time of one second or longer, this is a good thing!  In fact, the more you move the camera (within the bounds of the uniform wall/ceiling), and the longer the exposure the better, because we want to blur any non uniformity on the wall/ceiling: the dust on the sensor won't move so it will still be sharp.  Be sure to open the shot in your favorite photo viewing/editing tool and move around the shot at 100% (1:1) zoom so you can see the small specs if they exist.

It's confirmed: you have dust on the sensor

Now that you've cleaned the lens elements and have identified some spots in the frame, you want to clean the sensor to remove the debris.  I like to approach sensor cleaning in stages, performing the least invasive cleaning first and working up to the tougher cleaning techniques.  The first method of cleaning is to use a simple handheld blower bulb.  These are the little rubber bulbs with a little plastic tube that you can buy at almost any camera store.  While various forms of canned compressed air can blow more air, you're safer using a simple squeeze bulb as some canned air products can contain oil or may spray liquid (read very cold) gas which can harm the sensor or at least make your cleaning job even more difficult by spraying a residue onto the sensor.

Before beginning any sensor cleaning task, first make sure your camera battery is fully charged.  You don't want the shutter/mirror closing on you while you are cleaning!  While most cameras offer a "sensor clean" or "mirror up" function in the menu that was designed for cleaning, some (particularly older) cameras don't offer this feature or only offer the feature if you have an AC power supply.  In those cases, you can usually set the camera to manual exposure and set the shutter to 30 seconds.  You then have about 20 seconds to do your cleaning once you press the shutter release (you don't want to come anywhere near the 30 seconds and risk the mirror/shutter closing so getting out of there by 15-20 seconds seems prudent).   I prefer using the 30 second shutter instead of the bulb setting for cleaning when a specific cleaning option isn't present in the menus because: (a) you know how long you have before you have to remove the cleaning devices and (b) if you use the bulb setting, your finger may slip off the shutter button while you are cleaning.

Obviously, remove the lens from the mount first and then open the shutter so that you can see the sensor in the camera.  My preference is to hold the camera so that the lens mount is facing the floor.  That way, any debris that is blown out has a better chance of falling out onto the floor instead of just being blown around in the camera.  With the camera facing down and the shutter open, put the tube of the bulb blower up to the lens mount and center it in the middle of the hole.  I would recommend not putting the tube into the lens mount hole or close to the sensor because when you squeeze the bulb, there is a chance that the movement will cause the tube to strike something (mirror, shutter, or even sensor) in the camera.  So keep the tube just outside the lens mount hole.  Give a few quick bursts of air pointing the tube at the middle of the sensor.  Once you've done that, take another test shot (per the above instructions).  Did the dust specs go away?

If most of the dust specs went away with only one or two very small specs left, you've probably done a good enough job.  You may want to repeat the bulb cleaning per the above one or two more times to see if you can get all the dust removed but for the average Joe, be happy with only a spec or two!  Many times people go too far with different techniques and end up making it worse and/or inserting more debris into the system.  Also realize that the smaller specs are only likely to show up in "sky shots" using a very small aperture anyway.

A more thorough cleaning

So what if the simple blower bulb method doesn't work?  Maybe some of the specs on your sensor are "sticky" and will not come off with a simple shot of air.  There are many products on the market such as fine brushes, mild solvents w/swabs, and even "sticky tape" products designed to clean more stubborn debris from the sensor.  Again, my preference is to go with the lighter touch first.  In my opinion, the next phase is to try a sensor cleaning brush.  A Canadian company called Visible Dust makes good products that I have used on a number of cameras.  One Visible Dust product that I can recommend is the Arctic Butterfly.  The Arctic Butterfly is basically a very fine bristle brush on a rotating shaft.  You simply press a button for a few seconds and the brush rotates in the air rapidly (the unit is battery powered), flinging off any prior dust that might have been on the brush while statically charging the brush at the same time.  Once charged, you simply lightly swipe the brush over the sensor (never spin the brush while it is in the camera) and recheck for dust specs.

I find that a quick swipe with the Arctic Butterfly followed by a burst or two from the blower bulb often leads to the best results since it can be difficult to get the dust off the edge of the sensor sometimes and the static charge doesn't always attract all the dust.  If the brush method is still unable to remove those last few specs, you may need a "wet cleaning".  Visible Dust also sells swabs and cleaning solution.  A wet cleaning, your last resort to cleaning, basically consists of wetting a swab with cleaning solution and swiping the sensor with the swab.  As with any method, the most important part of the task is to follow the instructions explicitly!  Sensor cleaning at its worst, comes down to nothing more than a window cleaning job... a delicate one... and one done in a confined space.  Other than following directions, the best advice I can give is to first determine if you are up to the task after reading this article and possibly even the online instructions: Visible Dust has detailed illustrated instructions on their web site for example.  If you feel confident enough about taking on the challenge, just be gentle!  While sensors are more protected by things like antialiasing filters than most people might think, care is still needed to avoid damage to your camera.  Whatever cleaning method you choose, follow instructions, take your time, and be sure that the mirror/shutter never closes while you are doing things like brushing the sensor!  Shutter/mirror damage is actually more common than damage to the actual sensor.

But my camera has electronic sensor cleaning

Many newer dSLR's employ a method of electronic sensor cleaning where the camera basically shakes the sensor at ultrasonic (fast) frequencies to dislodge debris from the sensor.  While this feature is great to have and it does work (albeit the effectiveness varies widely across manufacturers and camera models), I'm not a big fan of electronic sensor cleaning.  When the electronic sensor cleaning cycle is done and that dust is gone from the sensor, where did it go?  You guessed it: somewhere inside the camera, and if all you ever did was perform electronic cleaning cycles, some of that dislodged dust is likely to make its way back onto the sensor eventually.  On cameras that will allow you to run the electronic cleaning cycle with the lens removed and the shutter open, I like to hold the camera with the lens off, shutter open, camera mount facing the floor, and then run the cleaning cycle.  If you do this in a room where the air is still, most of the debris will fall straight out the camera mount hole and onto the floor instead of being dislodged into the inside of your camera.  In any case, even with electronic cleaning devices, it is inevitable that eventually, you'll need to manually clean your camera's sensor as the electronic cleaning cycles cannot remove all (types of) debris.  Self cleaning ovens are nice too, but it doesn't mean you'll never have to wipe the inside of your oven.  The same goes for electronic sensor cleaning.  If the electronic cleaning cycle doesn't remove all the dust specs, don't get discouraged.  Just realize that such devices cannot completely eliminate the need for an occasional sensor cleaning.

Summary

For those who shoot with dSLR cameras, sensor cleaning will eventually become a fact of life; a part of normal maintenance for your camera.  If you're skittish about technical things, it might be best to take your camera to the local camera store when a cleaning is needed.  If you are not intimidated by the occasional techie type job, however, sensor cleaning might be worth a try.  In my opinion, it is certainly something achievable by the average person as long as care is taken and instructions are followed to the letter.  In addition, starting from the simplest cleaning method first (the blower bulb method) and working your way up, perhaps you can get a better idea about the type of cleaning you are capable of performing without jumping in the deep end first and then finding that you can't swim!

Mike Chaney

Stop "Cooking" Your Photos; Shoot Raw!

Background

In July 2006, I wrote a brief article about how shooting in raw capture mode could change your outlook on photography.  While the benefits of shooting in raw capture mode are as clear today as they were two years ago, still, a lot has changed in two years.  Have you changed, or are you still shooting in JPEG capture mode with your camera?   Let's take a look at raw shooting, how it can benefit you, and discover some of the tools used today to help you in your "raw workflow".

Raw versus JPEG

Many recent cameras offer the ability to shoot in raw capture mode as well as JPEG capture mode.  While JPEG capture modes are often labelled "Large", "Fine", or "Basic", the "Raw" menu selection gives you access to a shooting mode that is entirely different.  When shooting in raw capture mode, the raw data (basically the data straight from the sensor) is stored in a (usually proprietary format) file on your flash card.  While you can review your shots on the camera, you'll need to "develop" the raw data once you download the raw files from your flash card before you can view or print them using your computer.

So what's the benefit of shooting in raw capture mode?  In a word: quality!  When you shoot in JPEG capture mode, you're looking at a processed image.  Basically, your camera has taken the raw data and "cooked" it in order to create a JPEG image from that data.  If your white balance, exposure, and lighting are perfect, JPEG shooting might be OK.  Problems arise, however, when you need to rescue an underexposed or overexposed shot because the JPEG data has already been "truncated" to the exposure used by the camera.  Your JPEG has 256 steps or gradations for each color and in an underexposed shot, only the first 64 steps may be used.  When you brighten the photo, you see banding, noise, and other artifacts because you've truncated a 16.7 million color image down to about only 260,000 possible colors!

Unlike a JPEG, the raw data contains a much finer version of the data: one that has (usually) anywhere from 4096 steps to as many as 16,384 steps for each color.  Even with a 12 bit raw file that has 4096 steps or "shades" for each (red, green, and blue) color, instead of having only 64 steps to work with as with your JPEG, you now have over 1000 steps even on your underexposed image.  Now you can brighten the photo by adding exposure compensation without the ugly stepping patterns produced by the JPEG.

In addition to having more "granularity", raw photos also contain something called "headroom".  Headroom is an area of beyond-white steps that allow you to pull back exposure to recover blown highlights.  If you shoot a yellow flower only to find that a large portion of the flower is blown out (bright yellow with no detail), there's no way to recover the lost data with a JPEG.  If the same shot had been taken in raw capture mode, some if not all of the blown out highlights could be recovered because there's enough data in the raw file for it to capture steps (brightness values) beyond what would appear at maximum (255) in your JPEG's.

Simply put, shooting in JPEG capture mode is equivalent to being on a construction job, quickly measuring once, and cutting a board based on that one quick-and-dirty measurement.  After cutting, if you find out that you cut your board too short, there's no way to go back and make it longer.  The bottom line here is that JPEG files throw away data.  Don't cut your data based on the assumption that your camera (or you) will always meter and set up the scene properly!  Shoot in raw capture mode so you can make the most of your photos.  I've seen many photos that were destined for the recycle bin using the JPEG version but are easily rescued by using the raw photo.

Handling and developing your raw photos

The down side (if you can call it that) of shooting in raw capture mode is that you may not be able to just open them in your favorite photo printing tool and click the print button like you may have done with your JPEG's.  Two years ago, the process wasn't so simple.  You needed software to develop the raw photos first, and not all cameras came with such software, so you had to buy third party software costing from $100 to $200 just to be able to do anything with your raw photos.  To make matters worse, every manufacturer had their own proprietary format for the raw photos and even within one manufacturer, the raw format usually differed from model to model.  This made it difficult for any one software package to support all cameras, making you have to search to find a solution that would work with your particular camera.

Fast forward to August 2008 and things have changed considerably.  There are now open source solutions that cover almost every camera that can shoot in raw capture mode and while manufacturers still haven't made any headway into coming to an agreement on one international standard for raw photos, at least there are a wide variety of applications now that can handle almost any raw photos from any camera.

Even more interesting is the fact that some tools are now allowing you to treat raw photos like any other type of photo such as JPEG's.  The Studio Edition of my own Qimage software, for example, allows you to view, convert, print, and tweak raw photos just like any other supported image format while applying automatic exposure and noise reduction, thereby minimizing the amount of tweaking needed to get the best from your raw photos.  With more and more tools supporting raw photos in different ways, it's a lot easier to find the right tools to make raw shooting agree with your own preferred workflow.  Some people like to fiddle with each photo, trying different settings, while others just want to be able to get the best automatic rendition possible in order to minimize extra work.  Whichever boat you find yourself in, there are many raw tools to choose from.  Here's a quick list of some of the more popular "high end" third party solutions and their strengths.  Note that manufacturer solutions (that come with your camera or can be ordered separately) are not included.  Note also that the solutions below are, in my opinion, solutions that are acceptable tools to use to view, publish, or print final versions of your raw photos.  There are many more tools that "support" raw formats that I didn't list because while you can get an "image" from them, they lack essentials for final output like color management or proper color transforms to allow for accurate color.  So if you use a particular raw tool that is not listed, it's most likely because I didn't consider that tool a major player in the field of quality raw tools.

* as of July 2008

Summary

Shooting in raw capture mode can be a major advantage if you are interested in squeezing the most quality from your photos.  With some of the latest raw-capable tools on the market, shooting raw and being able to find an acceptable workflow for actually using the raw files has become much easier in the last year or so.  Not convinced?  Try shooting some photos in raw format before you make up your mind.  If your camera offers a JPEG+Raw shooting mode where you can actually capture both, try that and compare what you can get from the raw versus the JPEG images.  I did that at first, and now I've dumped JPEG shooting altogether as I can always get better quality from the raw photos and the added JPEG version just takes up space on my flash cards!

At the end of the day, taking the time to learn which raw tool(s) are best for you and working out your own personal raw workflow will pay dividends and can help you get better photos than ever.  So if you looked into raw shooting before and it seemed that the extra effort wasn't worth it, it may be time to give it another try.

Mike Chaney

Innovations in Camera Profiling

Background

In January 2007, I demonstrated a method for creating an ICC profile for your digital camera using a standard IT8 target.  The article covered how to set up and shoot the target and how to process the photo and create a profile using my Profile Prism software.  While the process was relatively simple, camera profiling has always come with some limitations and tradeoffs.  The biggest problem with camera profiling is being able to create a profile that works for all photos.  Because things like exposure, lighting, and white balance are always relative, creating an ICC profile from a shot of a reference target can always be problematic as the camera often uses different tone curves for different subjects and lighting. 

In addition, almost all cameras and developing software tend to "enhance" the tone curves to produce more vibrant photos because "linear" tone curves can look a bit dull.  The question I often got from people trying to create camera profiles was, "How can I create a profile that corrects color problems without modifying the tone curves or making the image look dull."  Until recently, this was not possible or at least not easily achieved because an ICC profile will always try to correct all aspects of color: tonality (brightness), hue, and saturation.  With the recent release of Profile Prism v6.5, it is now possible to create hue correcting profiles that correct problems such as reds looking too orange, blues looking too purple, undersaturation of yellow, and so on without changing the contrast chosen by the camera or developing software.  Let's take a look at how this is done.

The problem

A device (camera) ICC profile is a file that describes how to accurately reproduce color for that device.  Unfortunately "accurate" profiles are rarely what people want or need because they produce linear tonality in photos which can look dull: like there is a fog over the photo compared to what we are used to seeing.  In other words, we are used to seeing the linear/accurate result that has been modified to add a little "pop" to the photo.  This usually entails making the shadows a little darker and the highlights a little brighter.  This is done automatically by your camera or raw software and is often not optional.  If you notice some minor shifts in color when using your particular camera and you want to create a profile to keep that red sweater from turning orange, you might think an ICC profile is the best way to do this without having to edit the photo manually each time or eyeballing corrections using color channel sliders.  You'd be right, except when you create that profile, it'll not only correct the red/orange shift but will also "undo" the tonality adjustments that make your images pop.  That's the nature of an ICC profile and ICC profiling tools: they try to be all things at once, describing luminance, hue, and saturation accurately rather than how you may want to see it.

Another issue with creating camera profiles is that it has traditionally been difficult to impossible to create a good camera profile for JPEG images straight from the camera.  While creating profiles for raw developing tools worked reasonably well, how do you create a profile that corrects color issues in a JPEG that came from your camera: a JPEG that has already been "profiled" once to a color space such as sRGB or Adobe RGB but one that may have a few hue/saturation mistakes in certain areas?  Fortunately a solution now exists that can address both problems, allowing you to create camera "calibration profiles" for any raw developing tool, any camera, and any in-camera JPEG without changing brightness and contrast.

The solution

The solution to correcting color without dulling your images lies with the profiling tool.  It must be able to discern the underlying tone curve along with the "enhancements" made to that tone curve in order to reproduce the intended contrast.  Doing so will allow color (hue) corrections without changing overall contrast or brightness.  Most cameras and raw developing tools allow the photographer to select tonality settings such as "neutral" or "vivid" and those selections allow you to make a decision about contrast.  The biggest complaint and one that has traditionally been impossible to correct in camera (or in raw developing software) is one of hue shifts where colors look shifted in hue or under/over saturated.  Let's take a look at how to create one of these calibration profiles using Profile Prism v6.5:

1. Follow the steps in my January 2007 article, except

2. Choose "Gamma Match (Auto)" for "Tone Reprod. Curve"

That's it!  By choosing "Gamma Match (Auto)" in Profile Prism's "Tone Reprod. Curve", you are telling it to discover the intended/underlying gamma curve so that it can reproduce the same brightness and contrast, correcting only errors in hue and saturation.  This method should work in the majority of situations.  The manual gamma match options such as Gamma Match (2.2) or Gamma Match (1.8) only need to be used if the resulting profile appears to make images look too dull or too contrasty.  In those situations, Profile Prism may not have been able to automatically detect the proper curve due to the camera or raw developing software manipulating the curves too much.  In all situations, manually selecting either Gamma Match (2.2) or Gamma Match (1.8) will solve the problem and restore the original brightness/contrast.

Camera and raw software settings

The beauty of the gamma match camera profiling options is the fact that they can be used to create non-tonality-modifying calibration profiles without trial and error modification of color channels.  Due to the fact that they correct only color shifts and saturation problems, they can be used on any type of photo from your camera whether JPEG or raw.  But what about camera settings or raw developing tool settings?  What should you use?  The answer is simple.  Again, because these profiles are only correcting (presumably small) shifts in color and saturation, you would use whatever method you normally use to capture photos and then create a profile for those developed photos. 

For example, if you normally shoot in JPEG mode and you have your camera set to Adobe RGB color space, keep doing the same: take your shot of the IT8 target and then develop the profile based on that Adobe RGB JPEG from the camera.  The resulting profile is then assigned to the image.  The assigned profile overrides the initial Adobe RGB color space and assigns a profile that describes color more accurately than Adobe RGB.  By assigning the profile and using color management aware software (like PhotoShop or Qimage), your corrections are automatic because the software you are using will see and utilize the new (corrective) profile.  This is the preferred method since there is no second/additional profile conversion.  Your calibration profile in this case is doing nothing more than modifying how to interpret the RGB values in the photo.

If you are creating photos to be viewed in non color managed software such as photos that will be viewed on the web or via email, you'll want to convert from the camera profile to a standard color space like sRGB rather than just assigning the camera profile.  Whether you choose to assign your camera profile or convert from that profile to a standard color space, the profile should correct all color issues without affecting brightness and contrast.

When creating profiles for photos processed in raw developing tools, the same rule applies.  You can keep all your raw development settings in place and create a profile to assign after the photos have been developed.  Raw tools give you one additional option, however, in that some raw developing tools allow you to turn off color management and create a profile based on the raw data.  Most tools offer the ability to set your color management or camera profile to "none" or "embed camera profile".  This effectively turns off all color manipulation while only applying a tone curve (gamma).  This method is even better because you can profile the photo before any changes have been made to hue or saturation.  Raw developing tools that allow you to turn off color management usually offer a way to activate the new profile within the software so see the program help for your raw developing tool for more info.  Of course, if you use more than one raw developing tool, you must develop separate ICC profiles for each raw developing program as they all produce color slightly differently.

Summary

Camera profiling has always been hit or miss due to the fact that exposure, lighting, and other factors are not constant from shot to shot.  As a result, camera profiles often cause unwanted changes in brightness or contrast as the profile tries to "correct" for the preferred tone curve of the camera or raw developing tool.  I've found that people are almost always happy with brightness and contrast but often want to make subtle changes to color in order to correct issues with saturation or color shifting.  Because existing profiling tools are designed to correct all aspects of color including brightness and contrast, people often find that ICC profiles cause unwanted changes in brightness and contrast in addition to correcting hue and saturation issues.  This has forced most people to create manual color "calibrations" or macros by using generic color charts (often with only a few colors), eyeballing differences, and changing color channel sliders to compensate.

With Profile Prism v6.5, it is now possible to create hue/saturation correcting profiles that do not alter brightness or contrast.  Such profiles can be described as color calibration profiles and as far as I know, no other tool currently has the capability to create profiles that correct hue and saturation while leaving brightness and contrast untouched.  Being able to create calibration ICC profiles has some significant advantages over creating color calibration routines or macros:

• Creation of calibration profiles is fully automated and involves no guesswork or "eyeballing".

• Resulting profiles can be used in any color management aware software and don't depend on using a certain photo editor in order to apply changes.

• Calibration profiles can be used to convert batches of photos to standard color spaces for display on the web or via email.

• Calibration profiles are less time consuming to create because changes are based on actual/measured response rather than trial and error.

• Calibration profiles can address color corrections for your specific camera and/or lighting situations rather than a broader or generic correction for one model number and/or one type of lighting.

Mike Chaney

What to Buy: dSLR or Compact Camera

Background

Just a few years ago, the dSLR camera was reserved for professionals or amateurs who were very serious about photography.  The cost was high enough that it kept many casual shooters from even considering a dSLR.  The price gap isn't what it used to be, however, and it is now possible to get a good dSLR (with a decent lens) for a little more than double what you'd pay for a compact point-and-shoot camera.  Should you consider a dSLR for your next digital camera or is a compact right for you?  While it is impossible to cover every aspect of such a decision and how they might affect your personal choice, let's take a look at some of the driving factors that distinguish a dSLR from a compact/pocket camera!

Compact "pocket rockets"

The term "compact" camera can cover cameras from purse-size (about the size of a brick or smaller) down to truly compact cameras that fit in a shirt/pants pocket.  The latter have become more popular recently just because the technology that drives them has gotten smaller, allowing great photos in a smaller package, and if you are going to buy a small camera, why not buy one really small that can fit in your back pocket?  The Sony W-170 is a good example of a modern "pocket rocket".

Unlike years ago when you had to sacrifice a lot of features and quality to shoot with a compact camera, today's compacts offer much the same capability of dSLR's and many offer manual modes that rival the control you'd get when using a dSLR!  Also in the compact's favor is the fact that everything is matched and made to work together.  The lens is the proper size and quality needed to pair with the imaging sensor, the flash is mated to both the lens and camera capabilities, and so on.  Compact cameras often offer user friendly scene selections that allow you to choose "sports", "portrait", "night shot" and other modes and the camera takes care of the settings such as aperture, shutter speed, and sensitivity for you.  This allows the casual shooter to choose the right settings for the type of photos they are taking without having to know how each individual parameter affects image capture.

In addition to ease-of-use and features, the compact camera has one major advantage over the dSLR: size!  You can only take pictures if you have your camera with you and if your camera fits in your pocket, you are much more likely to have it with you than if you know you have to lug a big camera (with a lens that sometimes weighs more than the camera) around all day with the strap pulling at your neck.   If you want to take a camera to the amusement park for example, what are you going to do with your dSLR while you ride the coasters?  Your compact can go in your back pocket and take the ride with you.  Even when you go out to dinner, where are you going to put your dSLR and will you be sure to remember to get it from under the table when you leave?  Also, some sporting events, exhibitions, concerts, and other venues will allow compact cameras but not anything even resembling a professional camera so you might get stopped if you are carrying a dSLR.  These are things to consider when you evaluate how you will be using the camera: in what situations and in what type of environment. 

It isn't uncommon to buy a dSLR because they are "the talk" on the web only to find out that you leave it home more often than not due the complexity of using it or due to its size, and when you do use it you find that while it does have automatic modes, you need to know a little more about photography than you might with a compact camera.  Many of the compact cameras also offer movie and sound capture as well, something very few dSLR's can do.  While the video/audio modes of most compacts make them insufficient for good TV quality viewing or ripping to DVD's (except maybe the Canon TX1 and a very few others), they do allow you to capture those moving moments where you would otherwise miss them if you were carrying a dSLR.

The mighty dSLR

Next to step in the ring is the heavyweight champion: the digital single lens reflex (dSLR).  The dSLR is a big boy.  He's got one heck of a punch when he hits you but the featherweight compact is running circles around him taking shots while the heavyweight is still trying to find the right combo before making his first strike.  Of course, this analogy is a bit flawed since just about any dSLR can focus and shoot faster shots in succession than most pocket cameras.  Still, the analogy works to some degree since for the casual shooter, it can be easier to set up that initial shot using a compact camera.  The dSLR lumbers around waiting and hunting for just the right shot, but when he makes his move, that one shot can be a real knockout!  The compact, on the other hand, whisks around taking one "decent" shot after another but unlike the experienced heavyweight, the compact is more likely to take average shots that raise less ooh's and ahh's from the crowd.  OK.  Enough analogies... back to reality.  As far as size, the dSLR isn't one you would carry in a purse or certainly not a pocket.  The Nikon D60 is a good example of a "small" dSLR.

dSLR's offer some serious advantages to the serious photographer.  Really, there's nothing a compact camera can do (other than video capture) that a dSLR cannot as far as taking the actual photographs, yet there is much that a dSLR can do that most compacts cannot.  Hot shoe for bounce flash, wireless/slave and studio flash, interchangeable lenses for super telephoto shots and other "specialty" shots, tethered shooting, and excellent high ISO performance are just a few areas where the dSLR smashes most compact cameras.  You have to remember, however, that all of these things come at a cost.  If you want to get one of those super telephoto lenses to do some wildlife shots, you may pay more than you paid for your dSLR camera to get a good one!  And you may soon find that you need a camera bag as big as a suitcase in order to have all those goodies with you when you need them.  A long telephoto lens can easily be more expensive and substantially larger and heavier than the camera it is mounted to, so many lenses have a tripod mount where you actually mount the lens on the tripod and the less bulky camera hangs off the back suspended by the lens.  Of course not all lenses are that large, even some good super zooms, but you get the idea.

Another thing to consider when looking at a dSLR versus a compact camera is image quality.  How important is image quality to you?  Do you plan to do large prints where small imperfections in image quality might show in your prints?  If so, there's nothing better than a dSLR for image quality and that may be a factor for you.  Nearly any dSLR will beat a compact camera as far as overall image quality is concerned.  dSLR cameras have much larger image sensors which allow them to capture photos with less noise and more dynamic range.  A typical dSLR can shoot in darker conditions using ISO 400 and produce photos at higher quality (with less noise) than a typical compact shooting the same scene.  In fact, most dSLR's have less noise at ISO 400 or even ISO 800 than a compact camera shooting at ISO 100!  That's the price you pay for using a small camera with a small lens and a small sensor.  We can see this effect by viewing some sample images from compact cameras and dSLR's:

10 MP compact: Sony W-170	10 MP dSLR: Nikon D80

While there are obvious color and metering differences between the cameras, the above is a good example of the difference in quality you might expect when comparing photos from a compact camera to those from a dSLR: in this case, a 10 megapixel compact versus a 10 megapixel dSLR.  The above are crops from the original shots blown up by 200% (2x) to bring out fine low level detail.  Notice how the dSLR (right) renders much smoother, cleaner, and crisper detail.  The compact camera (left) renders the same part of the image with more noise and less visible detail.  The above is pretty typical when comparing image quality from compact cameras versus dSLR cameras and if the photos are printed large enough, a trained eye can frequently spot whether the photo came from a compact camera or a dSLR.

The relevant question at this point becomes: how noticeable are the quality differences in actual printed photos.  To answer that question, you have to ask how large you plan to print and how closely your observers tend to scrutinize the prints.  While the above shows a significant advantage in quality to the dSLR, that difference may not be evident until you print a 13x20 photo and examine it closely.  How often will you be doing that?  Will the difference still show (even if not as much) on a print with about half that effective "blowup": say 8x10?  Unfortunately this is a gray area where there is no clear cut answer.  In my experience, I can usually tell a dSLR photo from a compact camera photo by just holding an 8x10 from both.  At sizes smaller than 8x10, it can be very difficult to discern which is better.  While the dSLR photo may not jump out at you as being much better and the compact camera photo may not jump out as being noisy, many may see the dSLR photo as looking very clean or silky smooth, and just looking more like a professional photo even if you can't quite verbalize exactly why.  There is often simply a more "professional look" to dSLR photos while compact cameras tend to produce photos that look more like snapshots.  Some people equate the difference as the dSLR photos looking like real photographs and compact camera photos looking more like video captures.  Again though, that's really not noticeable until you start printing large photos.  Whether or not that is relevant to your own photo shooting is a matter of personal taste.

Summary

There are many factors to consider when buying a camera and if you're in the market and you don't know exactly what you want (or need) and you are considering both a compact "pocket rocket" and a dSLR, you might consider the points listed in this article.  In a nutshell, they are:

A dSLR may be better for you if you:

• Need maximum manual control over shooting parameters.

• Often operate in a studio environment or other "controlled" environment.

• Shoot in a wide variety of conditions where you may need multiple lenses.

• Frequently shoot under harsh conditions or lighting (high contrast, etc.).

• Need the best possible image quality.

• Do a lot of indoor shooting where red-eye and bounce flash are factors.

• Often shoot in low light where higher sensitivity or better flash are required.

• Need super fast focus and/or fast shot-to-shot continuous shooting.

• Plan to make large prints.

• Don't mind lugging around and keeping track of a larger camera.

A compact/pocket camera may be better for you if you:

• Would rather have user friendly shooting selections than manual control.

• Find it inconvenient to have to carry the camera around your neck.

• Plan to take your camera to sporting events, etc. where dSLR's are prohibited.

• Normally print smaller photos (8x10 or smaller).

• Often shoot under "impromptu" conditions and not studio type environments.

• Shoot mostly landscapes or people where precision/control are not paramount.

• Think quick focus and fast multiple shots are usually not necessary.

• Might need to shoot video from time to time.

In the end, good luck with whatever you decide.  Through the years I've learned that an acceptable snapshot is better than no shot at all.  If you love dSLR's as I do but you find that you often miss photo opportunities because you don't want to lug around the equipment needed to operate a dSLR all day, maybe at some point both would be best!  At the end of the day, you can only capture the moment if you have your camera with you.  Your dSLR will be next to useless if you find yourself leaving it home often because you don't want a heavy camera pulling at your neck all day or because the event you are attending (sporting event, concert, exhibition, or similar venue) doesn't allow "professional" cameras.  The simple answer might be to get both if you can afford them and carry whatever the occasion calls for.  Of course, that's not always an option for all of us nor does it even make sense if you're not into "professional" type shooting so if you do have to decide between a compact camera or a dSLR, hopefully this article will help you decide what is best for you.  Happy shopping and happy shooting!

Mike Chaney

Hacking for Charity

Background

Every once in a while I like to take a break from writing articles about how to do something technical and write about an interesting concept relating to technology.  In June 2007 I wrote an article entitled "Say No to Cracks" that discussed software cracking and reasons to avoid cracked software.  While that article focused primarily on why cracked software should be avoided, I also acknowledged the talent present in the hacking community in general.  In this followup, we take the concept of hacking one step further and we meet a man who is finding new ways to redirect that talent into something good!

Introducing Johnny

Johnny Long has become a good friend over the years.  I first met him a few years ago when he and his family moved in next door.  We started talking when our families got together for backyard picnics or a swim in the pool and we realized we had a lot in common, including a past filled with some of the same friends and colleagues who shaped our outlook on the digital world, and the world in general.  It was clear that we were both hackers at heart, but we chose to fulfill that passion in different ways.  While Johnny spends his time discovering and testing vulnerabilities in systems in order to help companies secure their networks, part of my own job was to find new ways to thwart hacking attempts and secure my own software against the hackers/crackers.  When Johnny wasn't filling my face with needles or hijacking my Ghost (both typical Johnny moves in Halo 3), I actually liked the guy even though in some ways, our careers were juxtaposed.  :-)  Little did I know a couple years later he'd come up with an idea that could really make a difference in this world!

Hacking for Charity

Ever watch someone do something with such talent that it made you wonder what they could do with that talent if it wasn't "misdirected"?  Sometimes you find someone so good at what they do that they really do need to quit their day job!  Johnny Long has found a way to take the raw talent of the hacking community and redirect it to a good cause!  The concept of using a hacker's talent to do good isn't new, but to recognize skill and be able to direct that skill at something that makes you feel good can turn computer skills into a passion.  Johnny's web site, Hackers for Charity, does just that!  You can see by the list of donors on the site that people are starting to take the concept seriously.  I've donated some copies of my own Qimage software to his cause and will be donating more to the cause in the future as I have confidence in what he is doing and where my donations will be used.  As for my readers here, I thought it worthy of mention as I believe it to be a novel concept on how to better utilize potential resources in the tech community.

Johnny has traveled to Uganda twice on extended trips to set up computer equipment in teaching environments, distribute swag (pens, pencils, paper, backpacks, etc.) to children there, and being able to make a difference in the local community is fueling his passion to help even more.  His idea of "hacking for charity" is starting to get recognition as he and/or his organization have made the headlines on CNN, CNBC, the Washington Post, The Wall Street Journal, and other media outlets.

Recognizing and rewarding talent

As someone who can relate to the excitement of being able to get a computer or system to do something that it wasn't designed to do, I can understand hacking even though my career demands that I work against it.  Part of the reward of being a hacker is that you are doing something different.  Hackers don't like fitting the mold.  Most of them don't want money for their hacking.  Everyone else gets paid money.  The average person in a technology related job puts on his/her suit, goes forth in the daily grind and commute, and they come home with some money to pay the bills.  The hacker wants more.  The hacker wants recognition that they've done something unique.

One of the reasons that hacking for charity is such a novel idea is that it is something that could actually work.  What better recognition than to know that you've used your unique skills to make a dent at making the world a better place!  I've heard it so many times, "Hackers are just evil" or "why would anyone want to make a computer virus".  It is not about evil or good/bad.  It's about people not wanting to be another stamp in the mold.  Hackers feel like they are enlightening the world by showing them a different way to look at things or that things are often not what they seem on the surface.  Sure, some do bad things and some do it for monetary gain... but so do a lot of white collar workers doing the daily grind.  There's good and bad in everything.  All you have to do is look to find it.  I for one, will be contributing to the Hackers for Charity cause so that in the future, when someone asks me "why do those people do that", I can respond, "maybe they'll eventually be the ones to make the world a better place."  :-) 

Summary

Hackers for Charity is a new concept where the talent and skills of hackers are being used to make the world a better place.  Check out their web site if you want more information on this interesting twist on how to better utilize some of the worlds best technology skills.  Knowledge is the way to the future, and we should be taking advantage of it wherever we can find it!

Mike Chaney

Full Frame Versus DX Cameras

Background

With some full frame cameras now on the market, most notably the Canon 5D and Nikon D3, there is quite a bit of chatter on the internet about full frame versus DX (cropped) cameras.  People keep lining up in their corners to watch a new fight posted by yet another pro photographer touting the virtues of full frame.  About the only thing that hasn't been done is a high dollar late night event on pay-per-view.  ;-)  Setting other camera features aside, what does full frame really do for you?  Is it time to dump your "old" DX camera with its 1.6x crop and buy into the full frame hype?  Let's take a quick look at this topic.

Full frame

"Full Frame" refers to digital cameras with sensors roughly the same size as 35mm film (36x24mm).  Most digital SLR cameras now commonly referred to as "DX" cameras use APS-C size sensors which are smaller at about 22x15mm on a 1.6x camera.  In comparison, most consumer point-and-shoot cameras use smaller sensors still, many coming in somewhere around 7x5mm.  The following figure will give you an idea of the relative sizes.

Size matters

So what difference does sensor size make if the camera takes good photos?  Of course, if you are happy with your photos, that's all that matters, but having a larger sensor does give you benefits that you may not realize you are "missing" with a smaller sensor.  First and foremost is image quality.  Due to the fact that larger sensors can hold larger pixels (when comparing cameras with the same resolution), a larger sensor usually is capable of greater dynamic range, less noise, and better high ISO performance.  Generally speaking, cramming more pixels into a smaller area will reduce overall image quality so having a larger sensor can alleviate some of the issues related to "pixel cramming".  In addition, smaller sensors with the same resolution (say 12 megapixels) cram more pixels into a smaller area which often results in the need to use the highest quality lenses.  In contrast, using a 12 megapixel full frame sensor, the pixels are larger and more spread out, making the lens a bit less of a factor for sharpness.

Image quality isn't the only thing that changes when you put a smaller DX sensor in an SLR camera.  Because other aspects of the camera remain the same, putting a smaller DX sensor in the camera equates to simply cropping the center out of the full frame image.  As a result, you end up with tighter framing of objects and a 35mm lens on a DX camera starts to look more like a 55mm lens on a full frame camera.  This may force you to back up from the subject and/or change your zoom.  In turn, depth of field will also be affected and you may notice that it is more difficult to get blurry backgrounds with a DX camera.  On the plus side (for DX), your 200mm telephoto lens will give you roughly the same framing of the subject as a 300mm lens, albeit with different depth of field (than a 300mm lens on a full frame camera).

If you are not used to shooting film or full frame, you may never notice these differences.  Those who have been shooting with DX cameras for years won't notice the difference in being able to get really soft, blurry backgrounds under some situations.  In addition, it is now very easy to find good quality lenses in the 17mm range, even in a super zoom, making your ability to get wide angle shots with your DX not as problematic as it used to be!

Light falloff

One down side to using a full frame camera is that you may run into situations where light falloff (sometimes incorrectly called "vignetting") is an issue at short focal lengths.  Having shot DX cameras for nearly a decade, I was surprised at how much light falloff was present on some of Canon's best zoom lenses at the wide angle end of the range when using the full frame Canon 5D camera.  Usually appearing as darkening in the four corners of the frame when shooting bright or uniform subjects, this light falloff issue with full frame cameras is shown at the very bottom of my 20D versus 5D review.  Note that light falloff doesn't indicate something "wrong" with full frame cameras, only that I had been spoiled by DX cameras almost never showing this issue and I was a bit surprised at how easy it was to see this problem in my photos when using the full frame 5D at the wide angle end with almost any lens, even when stopping down the lens.

About image quality

I've seen some posts on other web sites that show full frame cameras like the 5D coming out way ahead as far as image quality.  Personally, I find very little difference in image quality when comparing the 5D with some of the latest DX cameras like the Nikon D300.  A bit of an unfair comparison with the 5D being more than two years old and rumored to be replaced soon, but I don't find the exaggerated quality differences that I've seen on some other sites when comparing the 5D to the D300.  Instead, I find the D300 to be a good match for the 5D when it comes to image quality, at least at lower ISO's (below ISO 800).  At higher ISO's of around 800 and up, the 5D pulls ahead as expected, due to its larger sensor and greater sensitivity.  In controlled side-by-side testing of the 5D and D300, I've found little difference between the two and in fact, might give the sharpness edge to the D300 up to about ISO 400.  Here's a link to a comparison shot.  Both shots were developed from raw and only some exposure and a hint of fill light added to adjust for differences in the way the two cameras metered the subject.  Both shots were taken at ISO 200.

5D versus D300

I believe some of the web sites showing better detail from the 5D were running into issues with the lens or even some issues with the noise filtering on the cameras where too much filtering was used on one camera versus the other.  The only significant difference I can see with respect to image quality with full frame sensors is the ability to get better detail and less noise at higher ISO settings.  Even evaluating noise at high ISO is becoming difficult these days, however, due to the adaptive noise reduction being used in the latest models.  Click here for information on that subject if you haven't read last month's article.

Summary

Hopefully this article has provided some information on what to look for when considering a full frame versus DX digital SLR camera.  To be honest, I do a lot of wildlife shooting and the 1.6x crop factor equates to more "zoom" which can come in handy when shooting subjects that are far away.  I also feel that with many new (and good) lenses available in the 17-85 and even 17-200 zoom range, being able to get good wide angle shots is no longer a problem with DX cameras.  DX lenses also tend to be a bit lighter and cheaper due to their size, which can also be a plus.  For me, someone who has tried both and someone who didn't come from shooting film, I feel that full frame is more hype than hero.  Someone who does a lot of studio work or who shoots differently may disagree.  Thankfully (for me) this article is more about what to look for when considering whether or not to buy into full frame than an argument as to which is better for you!  Different people obviously have different needs.  All I can say at this point is that in my opinion, I don't think the existence of a few full frame cameras is going to push the DX models aside for a while.... if ever.

Mike Chaney

The Megapixel Race Continues

Background

In July 2004 I wrote my first Tech Corner article titled The Megapixel Race.   The article discussed the steadily increasing pixel count of both consumer and professional cameras and the tradeoffs associated with stuffing more pixels into the same area on the imaging sensor.  At the time (in 2004), manufacturers were increasing resolution by about one megapixel per year to keep the pot boiling and keep consumers coming back to the store to buy the latest models with higher resolution.  Is the megapixel race still on?  What has changed in the last four years, and are people still counting pixels when making decisions about which camera to buy?  Let's take a look at the current state of the market with regard to the ever changing technology.

A steady race

Back in 2004 when I wrote my original article on the subject of camera resolution, the top of the line prosumer dSLR had about 8 megapixels and I stated in that article that the resolution was growing by about one megapixel per year.  Well, here we are in 2008 and while the "top" is a little less easily defined these days, the high end dSLR's are now generally in the 12 - 13 megapixel range, so it's a steady race still running at the pace of about a megapixel per year increase in resolution.  Back in 2004, manufacturers were content with just cramming more pixels into the same area, however, creating higher resolution images that consistently degraded in quality year by year.  While the pixel count was going up, noise went up in proportion, bringing overall image quality down.  Cramming more pixels into the same area reduced the pixel size thereby reducing sensitivity of the pixels and increasing noise.  That's where things have changed a bit.  Manufacturers finally realized that they couldn't keep stuffing more pixels into the same capture area while letting image quality suffer, so a more balanced approach is being used today with better hardware and better software (in the camera) to compensate for the increasing resolution.

Traffic control for crowded sensors

If you keep trying to see how many (more) people you can fit into a compact car, eventually you'll reach a point where you realize the car needs some upgrades to be able to carry the load.  That's exactly what happened with the megapixel race.  While resolution is still steadily increasing, so is the technology behind the pixels.  Today's sensors have better on-chip noise control and better dynamic range.  In addition, cameras are relying more and more on adaptive noise reduction.  This adaptive noise reduction is basically noise reduction software that resides in the firmware of your camera.  Just a few years ago, shooting at ISO 1600 meant getting a very noisy image from your camera and then applying post-processing noise reduction using one of the more clever noise reduction software programs on the market.  Now manufacturers are building in this noise reduction right in the camera so that the JPEG images you get from your camera (or create from raw using the included raw processing software) are already filtered based on the ISO speed used for the shot.  Using more complex noise reduction in camera can give the "illusion" of lower noise levels at higher ISO speeds while in fact, the noise levels are still quite high but have been reduced by in-camera noise reduction techniques.

Paying the piper

The balance of resolution and signal-to-noise ratio is a bit like conservation of energy.  Noise reduction is a tradeoff.  You can lower noise, but it is inevitable that lowering noise will lower resolving power of fine detail as well.  Clever adaptive noise reduction algorithms can make this fact less noticeable by using things like edge detection to drive the strength of the filter, but the tradeoffs will still be visible if you look for them.  People seem amazed that the very latest digital cameras like the Nikon D300 or Canon 40D have higher pixel counts but substantially less noise than prior models yet when you really look at photos from these cameras, the tradeoffs are clear.  Sure, there is less noise, but the noise reduction on these cameras is so heavy-handed by ISO 1600 that there is a noticeable decrease in resolving power in order to achieve those low noise levels.  Overall, the image looks "cleaner" as people tend to notice noise grain before lost detail.  So perhaps this increasingly heavy noise reduction (more NR as you increase ISO speed) makes a better balance, but you're still paying the piper in the end!

Take a look at the two shots above.  The one on the left was shot at ISO 200 with a Nikon D300.  The one on the right was from the same camera with identical focus, shot at ISO 1600.  Without comparing to the image on the left, you might be amazed at the low noise levels in the ISO 1600 shot, however, placed next to the ISO 200 shot on the left, we can see how much detail is lost in the ISO 1600 shot due to the increased noise reduction used by the camera at the higher speed.  Note that these are both JPEG photos directly from the camera.

Putting it all together

While manufacturers have made great strides in hardware, increasing dynamic range while decreasing noise, you have to be careful when evaluating performance of newer cameras (particularly dSLR's).  We all have a tendency to open ISO 1600 or ISO 3200 shots and sit at our monitors looking for noise grain in the shadows.  Doing this may lead you to miss an important side effect of those smooth images: the fact that much of the detail has been smoothed over along with the noise grain that was removed!  Keep in mind that the very latest model cameras have gotten quite heavy handed at noise removal so it is important to compare both noise and available detail in the photograph to what you'd get at a much lower ISO speed.  This fact should be evident when online reviewers take the same shot with varying ISO and place them side by side in the review.  Keep in mind that I'm not saying "heavy" noise reduction is a bad thing.  Overall I think the high ISO photos from the latest dSLR's look very good.  Just keep in mind that no miracles are being worked with the latest and greatest cameras that claim incredibly noise free images from very high ISO speeds.  The answer is in the noise reduction... and with the right post-processing noise reduction software, you could probably come close to the same quality with an older camera.  The bottom line is that the increase in hardware performance is certainly there, but what sets these latest cameras out ahead of the pack is the more complex and stronger noise reduction being used in the processing of the data.

Summary

While the megapixel race continues at a steady pace of about one megapixel per year or slightly more, advances are now being made to increase hardware and firmware performance so that cramming more pixels onto the same size sensor will not equate to noisy photographs.  Keep in mind that the latest cameras are using some heavy handed noise reduction algorithms to achieve their much touted high ISO performance, however, so when reviewing high ISO performance from the latest cameras, keep an eye on more than just the amount of noise (grain) in photos: also take a look at how much detail gets "smudged over" by the noise reduction algorithms.  I personally find some of the noise reduction algorithms a bit too heavy handed in that when shooting JPEG's in-camera, there is so much noise reduction at (say) ISO 1600 that a lot of fine detail gets lost along with the noise.  For this reason, it is even more important to shoot raw photos with the latest cameras so that you can make the decision as to the proper balance of noise versus detail.  A JPEG from the camera that has been overly softened due to the ISO 1600 or ISO 3200 noise reduction cannot be rescued whereas you may be able to reduce the strength of the noise reduction on the raw file in order to bring back some of the lost detail if needed.  Suffice it to say that evaluating high ISO performance on the latest dSLR cameras is becoming a lot trickier.  You can no longer simply open an ISO 1600 shot and look for noise grain.  You must compare the shot against a lower ISO shot of the same scene to see just how much detail was lost to noise reduction.  I hope this article will help people better evaluate the performance of the latest cameras, particularly dSLR's, and will enable people to better see and understand the whole picture... pun intended!  :-)

Mike Chaney

On Spam Blockers and Blacklists

Background

As the amount of spam (unwanted solicitous email) increases in your electronic mailbox, associated countermeasures like spam blockers and black lists get more "heavy handed" by the day.  As a result, as spam increases, so does the risk that important/legitimate electronic mail will be blocked or deleted before you ever see it.  Are you sure you are getting all your (valid) emails?  Have you ever had a problem where someone claims to have sent you email, possibly multiple times, but you never get anything from the sender?  It's possible, I would argue likely, that you've been bitten by the tools that you think are protecting you such as a spam blocker or worse: your ISP (Internet Service Provider) blocking certain emails before they ever reach your spam blocker!  How can you reduce spam and still be sure you are getting all your "real" email?  How do you reach a balance between getting so many messages that the real ones get lost in a mountain of junk, versus being protected to such a degree that your protective measures accidentally delete or block messages you actually wanted to see?

Spam

After all the "do not call" lists, legislation, and other anti-spam initiatives that have been tried over the last few years, you'd think the spam problem would have gotten better and not worse.  Unfortunately, the problem has grown to a point that many find it difficult to even do business (reliably) via electronic mail.  Of course, part of the problem is that people continue to click on spam and the links within the spam message since there would be no market for spam if no one responded to it!  And of course, many spammers don't follow the law, or worse, exploit it so that they include an "unsubscribe" link in the spam as required by law, but clicking on it does nothing but validate that your email really exists and puts you on even bigger spamming lists!  Bottom line: never respond to spam, never click on "unsubscribe" links unless they relate to services that you know you signed up for, and never, ever click on links within a spam message!

One of the best things you can do is simply not respond to any spam.  If you see a spam that reminds you that you needed to go to a web site, order a product, etc. do not click on any links in the spam message!  Most spam messages contain links that, when you click on them, not only take you to the web page in question, but also credit the spammer with having a successful hit at the same time which is how many spammers get paid.  So if you see something that you absolutely must check out, don't follow the link in the spam message.  Just open your browser and go to the site manually or even better, Google the name of the company or web site and go to the site from the Google results.  This keeps the spammer from getting his/her money because there is no reference telling the company how you got there!  Using Google has an added benefit too, because you might not only get results for the product/company you are looking for, but you might also see that Google brings up a lot of reports about "rip offs", "don't use this company", or other indications that the web site you are about to visit is actually fraudulent or otherwise not a good place to do business.

Countermeasures

Of course, we all know what spam is and many of us use some sort of counter measures to keep spam out of our mail boxes.  The most common form of anti-spam is a spam blocker.  Spam blockers are usually just software packages that analyze your email as it comes in to your mailbox so that spam can be detected and either put into a "junk" box or deleted entirely.  Many programs exists that allow you to block spam and I won't go into which ones work better/worse since the point of this article is not how well they work, but that they all have flaws and will occasionally misidentify good email as spam!  Let's take a look at the two major categories of spam blocking tools:

User installed

The first category of spam blocking tools are those that are installed by you, the user.  These can range from virus scanning tools that double as spam blockers or email programs (or email program add-ons) that block spam inside your email program.  On the plus side, these tools are almost always user configurable and allow you to set the strength of the spam filter from low (very few emails will be improperly identified as spam) to high (where more spams might be caught but a significant number of good emails might be improperly flagged as spam).  These tools also usually offer the ability to either move the spam to a spam/junk folder or just delete it so that you never see it.  The biggest problem occurs when users set their spam strength/sensitivity too high and choose to delete mail identified as spam.  In these cases, a fair number of legitimate emails might be improperly flagged as spam and you'll have no opportunity to see those emails or correct the problem because the spam blocker deleted the messages in question.  So lesson one in using a spam blocking tool is to set your sensitivity so that only the most obvious spam messages are marked as spam and also choose to move the spams to a folder rather than delete them.  Doing this allows you to get a handle on how effective your spam filter really is and whether or not it is marking good messages as spam.  As soon as you choose the "delete" option, you are giving your spam blocking tool the authority to "vaporize" your email and that leaves you with very few options.  It's always best to start on the safe side to gain experience with the tools, and then increase their spam detection "strength" only when appropriate, i.e. when you have more experience with the tools and their effectiveness.

ISP installed

The second category of spam blocking tools are tools that are available to you through your Internet Service Provider (ISP).  Some providers offer web based spam blocking tools that you can access/tweak online.  Often these tools are described and supported via the web site of your ISP, and you may need your ISP's help to configure them.  If you have a "generic" email address like Hotmail or Yahoo, you may have access to your mail box via both a web page and your email program that resides on your computer.  When this is the case, it is often necessary to log onto the web site to view the contents of the "junk" folder, especially in cases where you are expecting mail but have yet to receive it.  If you use one of the free online email services and you are missing mail, the first place to look is in the "junk" folder found on the web site since those messages may never make it to your computer and your email program.  In addition to these user-configurable spam blocking/filtering tools, your ISP may use measures outside your control.  See "blacklisting" below for more details.

 

Blacklisting

Blacklisting is a third spam countermeasure that is so prevalent and so counterproductive that it deserves its own separate category!  Many ISP's use one of many online blacklists of (usually) IP addresses that they believe are operated by spammers.  If email is sent to you from one of these IP addresses (or sometimes just one that is close to it), your Internet Service Provider may block the email before it can ever be downloaded to your computer.  In all cases, this amounts to your ISP making the decision for you as to what is or is not spam since you have no control over this type of blocking.  This type of unilateral decision making is by far, the most destructive form of spam blocking because you have no control over it and it often results in legitimate emails being deleted entirely, as if they had never been sent.  Many times, a range of IP addresses are blocked for no reason other than the fact that a lot of outgoing mail is coming from those addresses.  So legitimate emails that are sent to (for example) customers from a particular company might be blocked due to your ISP deciding that it has seen too many emails from a particular IP address when in fact, the emails might be legitimate correspondence between a company and its customers or paid subscribers!  In addition, many spammers use mail "spoofing" where semi-random IP addresses are added to the header so you may find yourself on one of these blacklists just because some spammer decided to forge your IP address into the header!  The more correspondence you do over email, the more likely you'll be to fall victim to spoofing.

If you find that your messages are not being delivered to others and you suspect that you are on some online blacklist, your recipients may suggest that you take steps to remove yourself from the online blacklists.  Don't do it!  Instead, tell your recipients that you sent the email and their ISP is blocking it due to an error on their blacklist(s) and insist that their ISP deliver mail properly!  Put the onus where it belongs: on the people that are deleting your mail for no reason!  If you scramble to remove yourself from errant blacklists, you become part of the problem since those utilizing the blacklists should be held responsible for them working properly.  If you happen to be on the receiving end and you talk to someone who insists they have sent you mail numerous times yet you never get anything from them and you know your own spam blocking tools aren't the culprit, your ISP might be blocking the message(s) due to using a blacklist that has errors.  The onus is on you to inform your ISP that you will not tolerate them only delivering some of your email and deciding not to deliver others without your knowledge!  You pay your ISP (usually) for service and if they are not delivering all of your email, they are not serving you appropriately!  Spam blocking and decisions about spam are things that should be handled by the user, not unilaterally decided by an ISP working with tools that obviously do not work properly.

To make a long story short, if you suspect that your ISP is blocking email to you, they may be utilizing a blacklist that decided what to deliver and what not to deliver to you.  To know whether or not this is happening for sure, you may need to temporarily disable any user installed or online/web based spam blocking so that you can be sure your own tools are not the culprit.  If, after disabling all spam blockers for which you have control, you still don't get all your email, inquire with your ISP to see whether or not they use blacklists to block email before it ever gets to you.  If so, lobby them to stop using such (frequently errant) processes as you don't want them deciding which emails you do and do not receive.  Doing this will force ISP's to solve their own problems (like mail server overload) in other ways rather than pushing their own problems onto you, the people they should be supporting.

Summary

Spam blocking and blacklisting has become as much if not more of a problem than the spam they aim to protect you from!  If you utilize spam blocking tools, be sure you know how to use them appropriately or you'll risk losing important emails along with the spam you are fighting.  In addition, be aware that there is another level of spam blocking that happens "behind the scenes" for which most people are not aware.  Your ISP may be taking measures to block spam (spam blocking or blacklisting) and sometimes those measures can block legitimate mails as well.  Unfortunately, you have no control over this latter category except to demand that your ISP deliver all your mail and let you (or your own installed and configured spam blocking/filtering software) decide what is or is not spam.  If we all stop clicking on links in spam emails and we all demand that our ISP's deliver all of our email, the growing problem of not being able to reliably communicate via email would be over.  Sounds easy, right?  I guess, so does world peace... on paper.  ;-)  We are, after all, human.

Mike Chaney

A New Year's "Resolution": Sharpness EQ

Background

Once in a while when we find or create something truly unique, the idea gets left behind as we move on to new things.  Ever bake something that was so good that you ate it twice a week for a month and then just moved on to something else out of sheer boredom?  Ever come back to it a year later and remember how good it really is and felt like you discovered it all over again?  This article falls into that category where we revisit an old but very useful idea.  Let's take a look at sharpness variance in digital photos and ways to correct sharpness variances to bring out more presence or 3D effect in photos.

The problem

The vast majority of cameras on the market use CFA's (color filter arrays) to capture only one color at each pixel location.  The Bayer CFA above is by far the most common sensor type.  Notice that only one color (red, green, or blue) is captured at each pixel location on the sensor.  Sophisticated algorithms must be used to "predict" the missing two colors before you get to the final full color image that you see from your camera or raw conversion software.  To complicate matters, there are twice as many green pixels as red or blue, in part, in order to mimic the human eye and its greater sensitivity to green compared to red/blue.

If you take a picture of a subject with very little saturated color like a B/W resolution chart, snow scene, the moon, or other objects without saturated colors, it is easy to predict the missing colors because all three primaries (red, green, and blue) will have about the same brightness.  In these cases, the missing green and blue values will be about the same as the red brightness captured by a red pixel, red brightness at a green pixel will be about the same as the capture green value, etc..  Once you start photographing subjects with more vibrant colors such as fall foliage, colorful Halloween costumes, or the worst case scenario: a red rose, the amount of detail captured by the camera is significantly reduced.  As an example, consider the red rose.  A red rose of a particular shade will only excite the red pixel locations on the sensor, leaving very little (usable) information at the green and blue photosites (pixels).  For the red rose, your camera's resolution just dropped to near 1/4 of its total resolution due to the fact that the green/blue pixels on the sensor are contributing very little information.  In cases like this, the problem actually becomes visible in photos!  Your red rose may look a little soft or out of focus compared to the green leaves or brown parts of the stem that are in the same focal plane because leaving you to wonder if perhaps your camera didn't focus on the red flower as it should have.

If you train yourself to pick up the problem, it is quite noticeable!  A bright blue sweater in one particular photo may look a little out of focus compared to a gray sweater right next to it, you may find it difficult to get a truly sharp photo of a blue flower while the green leaves around the flower look sharp, and so on.  This sharpness discrepancy for different colors can alter the relationship between sharpness and depth of field and can take away some of the 3D effect or "presence" that is seen on cameras that capture full color (all three colors at each pixel) like the Sigma SD9, SD10, and SD14.  If you keep up with the reviews or visit online forums, you will likely hear a lot of buzz about how full color capture cameras like the SD9, SD10, and SD14 create photos with more 3D effect than other cameras.  The reason for that is in large part due to the fact that full color capture cameras do not suffer from sharpness discrepancies and capture all colors with the same amount of detail.  This leads to a much greater correlation between depth of field and focus which is what adds presence or 3D feel to photos.

The remedy

Fortunately, some years ago I found that you can take a (preferably unsharpened) photo and apply a special adaptive sharpening algorithm to effectively reverse the effect of color sharpness discrepancies.  The image sensor in your camera cannot capture all colors with the same detail, making certain colors (like saturated red and blue) look considerably softer than other colors such as gray or even green.  The fix is to apply sharpening in such a way that it sharpens saturated reds and blues the most, greens to a lesser extent but still more than grays, and so on.  While sharpening can't truly add information that has been lost to single color capture sensors, the adaptive sharpening technique can produce a more visibly pleasing result so that bright red detail doesn't look considerably softer than gray/white, green detail doesn't look twice as sharp as blue, and so forth.

I created an algorithm that effectively reverses sharpness discrepancies and called it the "sharpness equalizer", adding it to the repertoire of image enhancements in my own Qimage's batch filtering tool.  Simply select your USM (unsharp mask) and slide the equalizer slider to the right to bias the sharpening algorithm to compensate for sensor sharpness discrepancies.  Using values like 2 for the radius, 150 for the strength, and the equalizer slider all the way to the right (to try to compensate completely for sensor sharpness discrepancies) increases the 3D feel of images and improves overall clarity of photos.  I made my algorithm available to Uwe Steinmueller who also created a PhotoShop plugin that does the same type of adaptive sharpening.  See my earlier article on the Outback Photo web site for details on the plugin.

Since I have more than one dSLR camera and I'm always comparing the latest models to my full color capture SD14 for sharpness and 3D feel, I have recently rediscovered how effective the sharpness equalization tool really is and I find myself using it more often.  Here is an example that shows how detail such as red/blue can appear soft compared to B/W detail in the same focal plane and how sharpness equalization can help resolve problems of sharpness and depth:

Notice how the color detail (particularly the red) in the image on the left appears softer than the B/W detail in the upper left quadrant.  This is due to the sensor having less information to work with when capturing saturated colors.  The red detail in the image on the left almost looks like it is in front of (or behind) the B/W detail due to the red detail being a bit out of focus.  In reality, this is a test target on a flat sheet of paper so all of the lines in each quadrant should have the same sharpness.  Take a look at how sharpness equalization has corrected this on the right image.  The color (red, green, and blue) detail is now just as sharp as the B/W detail in the upper left quadrant.  The sharpness equalization has now effectively restored sharpness in the photo and along with it the proper depth of field.  To see examples of how this works with real photos, see my earlier article from Digital Outback Photo or download a trial of my own Qimage batch printing/processing software and look in the help under unsharp mask to see how you can try this process on your own photos!

Summary

If you're like me and you want to get the most detail out of your photos but you always find something missing when capturing bright colors, take a look at the information in this article.  You may be noticing a discrepancy in sharpness/detail produced by your camera due to the way your camera captures color.  Using sharpness equalization can help you gain more "3D effect" or feel from your photos and increase the overall presence of the scene.

Mike Chaney

Border Patrol: All About Borderless Printing

Background

Most newer inkjet photo printers now offer options for borderless printing and using those options leads to a number of questions that I've seen from people confused about certain aspects of borderless printing.  Have you tried borderless printing only to find that it crops more of your photo than indicated on screen?  Are you using borderless mode to print multiple photos on a page but you've discovered that your photos are now larger than you specified in your printing program?  Have you tried printing three 8x10 prints across a 24 inch roll of paper only to find part of the left 8x10 missing and a white sliver beside the 8x10 on the right?  If so, this article is for you!

Understanding the tradeoffs of borderless printing

Before going into the methods and madness of borderless printing, let's discuss some of the tradeoffs involved with borderless printing.  First and foremost is the fact that with borderless printing, you are trying to print a photo (or multiple photos) that fit exactly on the page with no runoff or slack on any sides.  For example, if you are printing an 8x10 photo on 8x10 borderless paper, the objective would obviously be to print that 8x10 photo so that it aligns perfectly to the 8x10 page.  This unfortunately is nearly impossible due to the fact that printer paper loading and feed mechanisms are not perfect.  If the paper loads just a fraction of an inch further to the left than expected, you'll end up with the right side of your 8x10 cut off and a white sliver of paper showing on the left edge of the paper.  Even a hundredth of an inch can make a visible difference here.  Paper loading and feed mechanisms have tolerances higher than that as they simply cannot load and feed paper that accurately every time.  The paper feed mechanisms may also load paper slightly differently depending on how many sheets are loaded in the tray.  You may find a white sliver missing on the left when 20 sheets are loaded and the white sliver may move to the right when the last sheet is loaded.  This variability makes it nearly impossible to print exactly an 8x10 on 8x10 borderless paper, exactly a 4x6 print on 4x6 borderless paper, and so on.

To compensate for the above, printers usually offer the option (or mandatory use) of something called expansion and overspray.  To avoid white slivers of paper from showing on your borderless prints, expansion will actually expand the print to a slightly larger size, printing part of the print off the edge of the paper and onto an overflow (sponge or other material) off the edge of the paper.  Your 8x10 may be expanded to 8.2 x 10.2, for example, printing two tenths of an inch of your print off the edge of the paper.  Printing beyond the edge of the paper will obviously eliminate white slivers along the edges and will hide the fact that the print isn't aligned perfectly on the page where it should be.  Obviously if your photo is tightly cropped, you may notice that some of the photo is missing.  Many people disable the expansion to avoid parts of the print printing off the edge of the paper and then spend countless hours pulling their hair out trying to get borderless prints aligned just right to avoid alignment problems like white slivers on one edge and cropped image on the other edge.  The first step in being successful at borderless printing is realizing that trying to exactly fill your borderless page by printing a photo that is exactly the same size as your paper is nearly impossible.  If borderless printing and exact sizing is a must, you may have to reach some compromises. 

It is also important to understand that print quality may be slightly reduced near the edges of the paper.  You may actually get a warning to this effect when you select the borderless option in the driver.  While any reduction in quality is usually minimal and not visible on most photos, it can be an issue when printing graphs or line art that include precise edges.   Let's take a look at the most common borderless printing scenarios and see if we can make things a bit easier but before we do that, let's check out some common driver options to make sure we understand how the print driver is handling borderless printing.

Print driver options

The vast majority of print drivers offer at least some control over the amount of size expansion and related overspray will be used when printing borderless.  Typically labeled "amount of extension", "expansion" or some other related term, this control normally appears as a slider near the check box for "borderless" in the driver.  Sliding this control to the left results in the minimal amount of expansion/overspray and sliding it to the right results in more expansion/overspray.  Some drivers actually allow you to turn expansion/overspray off completely when the control is dragged to the left while other drivers require some minimal level of expansion and do not allow you to turn size expansion and overspray off completely.  Realize that whenever expansion is on, the printer will expand your prints and make them slightly bigger than what was selected.  A 4x6 may become 4.1 x 6.1 inches, a 5x7 may become 5.15 x 7.15 inches, etc..  And of course, the more expansion that is being done, the larger the print becomes, and the more (of your photo) gets lost off the edges of the paper.  This may not be important when printing a single photo on a borderless page but if you are trying to squeeze four 4x5 prints onto a borderless 8x10 sheet, be prepared to have two edges of each 4x5 print cropped off a bit as they will be slightly larger than 4x5 in size and the outside edges will print slightly off the paper as a result.

Some print drivers, particularly drivers for large format Epson printers, give you the option of whether you want the driver to expand prints in the typical fashion or you want to do it yourself.  In most Epson drivers, the options are labeled "Auto Expand" and "Retain Size".  Auto Expand works as above, with the driver adding some level of expansion depending on where the "expansion" slider is set.  Retain Size takes a little different approach.  It expands the size of the page beyond the edges of the paper and you have to decide how you want to handle the expansion/overspray.  With the Retain Size option, a 24 inch roll may show as 24.23 inches wide in your printing software.  The extra .23 inches actually print off the edge of the paper: about .115 inches on the left and .115 inches on the right.  If you were to print three 8x10 prints across the paper starting at the left edge of the printable area (that 24.23 inches), the left .115 inches of the first 8x10 would be missing as it printed off the left edge of the paper. 

As you can see, using the Retain Size option simply allows you to address (print on) areas that are beyond the left and right edges of the page!  Your 8x10 prints will be exactly 8x10 inches and you have the option of placing them wherever you want on the (expanded) page, including .115 inches off the left edge of the paper up to .115 inches of the right edge of the paper.  When printing any combination of photos that add up to 24 inches such as a 24x36 print, three 8x10 prints, etc. be sure to start by centering all prints on the page.  That will leave .115 inches on both the left and right sides of that 24.23 inch width and will give you a good start.  As pointed out above, however, you may need to adjust margins slightly (using fractions of an inch) to adjust for "slop" in the paper loading mechanism.  Now let's take a look at some common borderless printing scenarios.

Printing a single photo covering the entire page

The simplest borderless printing scenario involves printing a single photo so that it covers the entire borderless page.  Some typical setups would be printing a 4x6 on 4x6 photo paper, an 8x10 on 8x10 paper, etc..  By far the easiest and most trouble free method of doing this is to allow at least some expansion so that some of the photo prints off the edges of the paper in order to hide the fact that the print might not be perfectly aligned.  When you print a 4x6, a fraction of an inch may be missing since it printed off the edge of the paper, but you'll get nice clean prints with no white slivers to clutter the edges.  Of course, when doing this, it is important that you don't crop your photos very tightly.  If your photo contains some type of framing that you added at the edges of the print or you cropped so tightly that heads, shoes, or other features are already at the edge of the photo, you'll never be happy with overspray/expansion because it'll always crop just a little more than what you see on screen (from whatever program you are using to print).

If you are working with tight crops and you must print exactly a 4x6 photo on 4x6 paper without any overspray/expansion, you are in for at least some minor headaches.  There is simply no way around the fact that you will likely need to make some minor adjustments.  First, your driver may not even offer the option of turning off expansion completely.  If it doesn't, you'll have to use a program like Qimage that knows how to disable the expansion outside the driver.  Once the expansion has been disabled, you'll now be getting exactly a 4x6 inch print (or whatever size you chose) and your prints will no longer be "enlarged" but you may find that it doesn't align perfectly on the paper, leaving a white sliver on one or more edges of the paper.  At that point, you'll have to make slight adjustments to the margins, often using both negative and positive margins, to compensate for the slop in your printer's paper loading and feed mechanism.  A method for this type of adjustment is outlined in the Qimage help file here.  Just remember to never use negative margins (if they are even allowed in the software you are using) unless you are printing borderless because that's the only time negative margins (going beyond the edge of the paper) make sense.

Printing multiple photos on borderless paper

In certain situations, it is convenient and cost effective to use borderless printing to fit more photos onto a single page.  For example, you may want to print three 4x6 photos on a single 8x10 borderless page.  The same processes and tradeoffs are at work here (expansion versus alignment) but people are often even more confused when printing multiple photos on borderless paper when they discover that their 4x6 prints are not really 4x6 when printed.  Instead they are either slightly larger or they have one or more edges that appear more cropped than expected.  Of course, this is the driver's size expansion doing its dirty work!  Again, you could disable the expansion per the previous paragraph, but you'll again be faced with trying to make near microscopic adjustments to margins to compensate for slop in the paper loading and paper feed mechanism.  While it is relatively simple to make these compensations, your printer is likely not always consistent in exactly how it loads paper so your adjustments may only work with a certain type of paper or with a certain number of sheets loaded.  The exact position of the page may differ when variables like the number of sheets in the tray change.

Other surprises related to print size

The expansion and overspray related to borderless printing can cause prints to be larger than expected, leading to complaints about getting the wrong size print or prints that are too cropped.  In this case, the print driver itself modified the print to make it larger.  Be aware that in addition to borderless printing, there are other options in some print drivers that can cause surprises related to print size.  Options like "fit to page" can often be used in the print driver when selecting a paper size that exceeds the physical limitations of the printer.  For example, if you try to select a paper size of 18x25 on a printer that can only print 17 inches wide, the driver may actually allow you to select that 18 inch width using a "fit to page" option where everything is scaled from 18 inches wide to 17 inches wide.  This causes the driver to "lie" to your printing software, telling it that it actually is using 18 inch wide paper.  When you print an 18 inch wide print, however, the driver will scale the print down to fit it on the (true) 17 inch wide paper and you'll end up with prints that are smaller than you expected.  Personally, I don't like print driver options that "corrupt" data in this way by modifying it after it has been sent to the printer, but those options are pretty standard for most print drivers, so just be aware that no matter what software you use to print, if the size you get from your printer disagrees with the size shown in your printing software, it is almost always the print drivers fault for modifying the data that has been sent to the driver and producing something other than what was specified in the print job!

Summary

If you are not getting the sizes or spacing you expect with borderless prints, consider the information in this article and the fact that expansion/overspray may be involved.  Printing a single photo on borderless paper is often not a problem because we often don't care about 1/16 inch being printed beyond the edge of the paper.  When precision is paramount, however, as it would be when trying to fit three 8x10 prints across a 24 inch roll of paper, be prepared to spend the time needed to turn size expansion off and make miniscule manual adjustments to margins to get things just right.  It can be a painstaking process to align prints on a borderless page so that all edges of the photo just touch the edges of the paper.  Fortunately if you are using Qimage, you'll only have to make these adjustments once for each configuration you are using since Qimage will allow you to save all print related settings including driver selections in a printer setup that can be loaded at any time.  Since some variables involved with this fine alignment may not be available in the driver (such as the ability to disable overspray/expansion and the ability to use negative margins), just saving driver settings inside the driver (if your driver allows that) may not be enough.

This article should not only give you some examples that will work properly for borderless printing, but also give you enough background to understand the process of borderless printing to the point that you can deal with some of the common pitfalls and headaches that can be synonymous with borderless printing.  Borderless printing is a powerful and often paper saving feature that when combined with the right knowledge, can prove to be rewarding in the end.

Mike Chaney

Using Matte, Semi-gloss and Glossy Paper

Background

There are such a wide variety of papers available for your inkjet printer that selecting a brand and type of paper can be mind boggling.  Is brand XYZ paper compatible with your printer and if so, what are the benefits of matte, semi-gloss, and glossy paper types?  Let's take a look at some of the pros and cons of using matte, semi-gloss, and glossy paper for your photos.

Manufacturer Versus Third Party Papers

If you use paper made by the same manufacturer as your printer, try to check the paper type selections in your printer driver to be sure the paper is specifically listed.  If it is, life is made simpler due to the fact that you know the driver already has a selection compatible with the paper you are using.  When it comes to third party papers, things can get a little tricky.  You often end up going to the paper manufacturer's web site to see if your printer is listed as "compatible" with specific papers.  Even if your printer is listed as compatible with a particular paper, however, be aware that you may need to select specific settings in the print driver that are not immediately obvious like selecting a paper type that doesn't match the paper you are using, adjusting color settings per the paper manufacturer, or even using specific ICC profiles that can be downloaded from the paper manufacturer.  Also be warned that just because a printer is listed as "compatible" with a particular paper doesn't mean that it really works well with that paper!  To be sure, try Googling the type of paper and your model printer to see if others are having success with the combination.  I've seen some claims of compatibility that I'd really have to question because in some cases, I'd call the paper incompatible because the paper exhibits significant bronzing, highly visible dot patterns, or other artifacts that I find unacceptable.  Suffice it to say that unless you can find others on the web who recommend the combination, stick with paper made by the printer manufacturer to be safe.  There are plenty of excellent third party papers out there by various manufacturers, some of which I hold in higher regard than even the manufacturers own paper, but you have to do some research before you can determine if the paper is truly compatible and does not have other issues like longevity problems with certain inks.

Matte Paper

Matte paper is excellent for displaying photos such as large panoramas that must be displayed "naked" (not behind plastic/glass) in an environment where light reflections can be an issue.  Since you don't get any glare at all from matte papers, matte paper is a good choice for displaying a 4 foot panorama in a camera store under mixed lighting especially where the prints are displayed high on a wall and reflections from overhead lights can be a real issue.  Matte papers are generally not as durable as semi-gloss (sometimes called luster) paper or glossy paper as handling of matte prints can sometimes cause abrasion marks similar to running your fingers across a suede or microfiber material.  As a result, matte paper is not generally suited for prints that are to be handled in their naked state.

One real issue with matte papers is that they have less dynamic range (contrast) and a smaller gamut than semi-gloss or glossy papers.  Some like to say that they have less "apparent" range because that range is dependent on how the light reflects or is scattered off the surface of the paper, but the line between "apparent" and "actual" is a very fine line when it's the light that reaches your eyes that is important.  Regardless of the semantics, matte papers will generally have duller colors and less contrast than semi-gloss or glossy papers.  This fact even bears out when profiling different paper types as the profiling equipment/tools will find a smaller color gamut and less dynamic range for matte papers and will therefore have to make more compromises when creating the profile.  Here's an example of the color gamut of a matte paper and glossy paper profiled under the same conditions, with the same profiling software, for the same printer (Epson 2200):

The wire frame shows the color gamut of the glossy paper and the solid surface shows the color gamut of the matte paper.  As you can see, the glossy paper has a significantly larger color gamut, meaning that the same print will appear more vibrant on glossy paper compared to the matte paper.  Even though the difference in gamut size can be smaller (or larger) than that depicted above, generally you'll get more vibrant colors from a glossy print than you will with matte prints.  Mounting matte prints behind glass or plastic can compensate for this to some degree, but due to how the ink droplets interact with the paper itself, matte prints will always have a smaller gamut and less contrast than glossy prints.

Next is the issue of resolution.  Again, speaking in generalizations (since there are a wide variety of papers that one could compare), glossy papers produce prints with the highest level of "micro detail": that is, detail that can be seen under very close examination of the prints.  This is due to the fact that matte papers tend to "soak" up more ink than glossy papers, causing each ink droplet to be a little more spread out and a little less defined on matte paper.  The bottom line for matte paper is that it serves an important role but due to color vibrancy and resolution limitations, should be used appropriately and should probably be limited to uses where light reflections and glare are a major concern.  Matte papers are also very good when you don't necessarily want that "wet" look but would rather have a softer feel to your photos.  They can also be more cost effective when displaying large prints that will not be viewed up close as distant viewing doesn't require fine resolution/detail.

Glossy Paper

Glossy papers generally offer the widest color range and best resolution, but they suffer from glare which can be a problem under certain lighting conditions.  As pointed out above, glossy paper is excellent for photos that will be handled in their "naked" state.  They may show fingerprints, but they are usually quite durable, to the point where you can easily wipe off smudges or fingerprints without harming the prints.  Profiling glossy papers is also often easier as glossy papers offer a "no compromises" quality that truly brings out the best in color and resolution that your printer can offer.  They are often not the best choice, however, for scrapbooks or glass mounting as they can sometimes stick to the surface that is mounted against the printed side of the paper!  For mounting behind glass or plastic sleeves, semi-gloss may be the best compromise.  Also be aware that if you do decide to go with third party papers, glossy papers are the most particular about compatibility with certain printers.  That is, it is easier to find third party glossy papers that don't work well with your particular printer or have gas/light fade problems with certain inks.

Semi-gloss Paper

Semi-gloss or "luster" papers offer a good compromise between glare, color range, and durability.  With a color range close to that of glossy paper, you can be sure you are getting the full power of your printer while at the same time reducing glare and smudges.  Semi-gloss papers may not completely eliminate glare but most of them reduce glare to a point where it is not an issue except under the most extreme lighting conditions and viewing angles.  Where glossy used to be my favorite paper type for getting the most color vibrancy and detail from any printer, some of the latest semi-gloss offerings are quickly changing my mind or at least making it a toss-up between glossy and semi-gloss paper when matte paper is not specifically called for.

Other Paper Types

Of course, we can also choose from canvas, textured, and other "fine art" type papers like "photo rag" papers.  These are normally outside the range of what a "typical" user would normally encounter, but suffice it to say that most of the canvas and fine art papers fall (loosely) into the category of "matte paper on steroids" except for the few glossy fine art papers.  Canvas and photo rag paper follow the general characteristics of matte papers with some caveats.  If you are interested, Google is your friend.  A little research goes a long way when determining whether a particular paper is well suited for your model printer.  Keep in mind, however, that most photo rag papers soak up even more ink than your typical matte paper and that may force you to increase ink intensity in your print driver to get decent contrast and good blacks.  Of course, that will cause a corresponding increase in ink consumption.  Personally, I'm not a big fan of most photo rag papers for this reason.

Summary

I often get asked about when it is best to use certain paper types or get questions such as "why use glossy paper at all if it causes glare".  I also get asked why it often seems like more work is required when creating ICC profiles for matte papers compared to glossy papers.  Hopefully this article has answered a few of those questions and will at least give you a start if you are wondering about the pros and cons of matte, semi-gloss, and glossy papers.

Mike Chaney

Posting Photos on the Web

Background

So you have a new dSLR camera and you've been taking some great photos.  You want to share them with others and you've found an online photo hosting service where you've uploaded some photos but you notice that after they have been uploaded, they look dull or washed out when they are viewed on the photo hosting web site.  Where did you go wrong?  They looked great until you uploaded them to the web!  In this article, I discuss a common mistake that can cause color problems when uploading photos to photo sharing web sites.

Your Camera's Color Space

If you are not familiar with color spaces or need a refresher as to why your camera may offer more than one color space, you may want to check out this article before going further.  If your camera is set (via the menu options on the camera) to sRGB color space or the camera doesn't offer any color space selection, you should have no problem just uploading the original files to photo sharing web sites since sRGB is a reasonable color space for web viewing.  Web browsers generally are not color management aware, which means they can only display the raw image "as is" on screen.  Since sRGB is a reasonable match for most monitors, images coded in sRGB color space should look fine.

You've read about the virtues of larger color spaces like Adobe RGB, however, and you've set your camera to Adobe RGB color space via the camera menu option.  When posting images on a photo sharing web site, here's where the trouble starts!  If you upload an image that has been captured in Adobe RGB color space (or converted to Adobe RGB via your raw conversion tool of choice), the image on the photo sharing web site will be in Adobe RGB color space on the web site.  When someone goes to that site and opens the image with their web browser, they'll be looking at an Adobe RGB image on a screen that is best suited for an sRGB image.  This is due to the fact that the web browser ignores the color space tag in the image since it is not color management aware: it simply "dumps" the image onto the screen.  When this happens, colors can look dull, washed out, and some colors can appear shifted or just wrong. 

Adobe RGB	sRGB

Take a look at the photos above.  The one on the left is what the photo would look like if you had shot the flower in Adobe RGB and simply uploaded that file to a web page or photo sharing site.  The photo on the right is the same photograph converted to sRGB color space prior to uploading the image.  As you can see, the colors look quite dull and lifeless in the Adobe RGB version.  Again, this is due  simply to a mismatch in how your monitor handles color and how the color was saved in the image.  It is not an indication that there is something wrong with Adobe RGB color space!  The fact that your monitor is better suited (closer to) sRGB is what makes the sRGB version look closer to correct.

A Time and a Place for Adobe RGB

Adobe RGB has a larger color gamut (range of colors) and is therefore well suited for reproducing photographs in professional photographic tools, particularly when printing since printers can actually reproduce a wider range of colors than your monitor.  If you were placing photos on a web site for professional photographers to download and edit or print on their computer rather than just displaying the images on the web, it would be appropriate to use Adobe RGB.  So Adobe RGB is appropriate when you want people to be able to download and reproduce your photos offline.  This ensures that you get the larger color gamut of Adobe RGB and most professionals who intend to download and use the images on their computer will realize that the photos may not look "up to par" when just viewing them in a web browser.  For most applications, however, you'll want your images to be in sRGB color space so that people can just click on the photos in their web browser and get reasonable color rendition without having to download the files and pull them up in a photo editor or other color management aware application.

Converting to sRGB Prior to Uploading

While you've been happy shooting in Adobe RGB color space and you've had no problem editing your photos in your professional photo editing application or printing them from Qimage as those applications are color management aware, it would seem your use of Adobe RGB color space is now causing problems for you when you want others to view your photos on the web.  Do you need to switch back to shooting in sRGB color space to avoid this hassle?  The answer is emphatically NO!  You can keep on shooting in Adobe RGB to get the extended color capture range (that your printer can use) and simply convert those Adobe RGB images to sRGB prior to uploading them to the web.  Don't worry, this operation is simpler than it sounds!  You could always do it the hard way by opening each photo one at a time in your favorite photo editor, converting to sRGB, and resaving, but if you have a batch processing application like Qimage, you can make sRGB copies of all your Adobe RGB photos in one batch processing step.  In Qimage, here are the steps to create sRGB copies of a batch of Adobe RGB photos:

1. Add Adobe RGB images to the queue by selecting/dragging thumbnails.

2. Right click in the queue or on the preview page and select "Convert Images".

3. Under "Save Options", select the file type for the new files (JPG, TIF, etc.)

4. Check "Perform a profile to profile (ICC) conversion".

5. Delete any text in the "From" box: the word <input> should appear in the box.

6. Click the "...." button next to the "To" box and then click "Utility Profiles".

7. Select "Adobe RGB".

8. Click "OK" and sRGB copies of all images in the queue will be created.

If you know you want downsampled JPEG's for the web, here's an even easier way:

1. Add Adobe RGB images to the queue by selecting/dragging thumbnails.

2. Right click on queue/preview page and select "Create Email/Web Copies".

3. Make sure "Convert to sRGB color space" is checked.

4. Select resolution and JPEG quality and click "Go".

5. Unless you specify an output folder, sRGB copies will be in a {Q}e-mail subfolder.

Summary

Be aware that web posted photos can look dull or display with inaccurate color if you are shooting in (or converting your photos to) Adobe RGB color space and then uploading the Adobe RGB images directly to the web.  To solve this problem, simply convert images to sRGB color space prior to uploading them to your web page or photo sharing site.  My own  Qimage software offers batch conversion to create sRGB copies from multiple Adobe RGB images in one shot (see above), making shooting in Adobe RGB and uploading to the web less time consuming.  By shooting in Adobe RGB, you can reproduce a wider range of colors for printing photographs and still convert to sRGB when needed for web display.

Mike Chaney

Why Digital Cameras Have Mechanical Shutters

Background

Ever wondered why digital cameras, particularly high-end digital SLR's, have mechanical shutters?  The sensor is electronic, so why can't it be told to simply sample the light for the length of time specified by the shutter speed?  Why can't the sensor just start accumulating light (what is sometimes referred to as a "charge"), wait a specified length of time, and then stop accumulating light at the end of the exposure time?  Let's take a quick look at the reason mechanical shutters are used in digital cameras.

The Shutter Itself

Digital cameras use several different types of mechanical shutters, but all of them serve the same purpose.  They block light from reaching the sensor when closed and move out of the way to let light accumulate on the sensor while open.  Of course, the first thing that comes to mind is that the sensor, being an electronic device, should be able to simply turn on/off electronically.  Why is the shutter even needed?   Well, in fact, many cameras do use an electronic shutter that simply turns on/off the "light reading" capability of the sensor when needed.  Many pocket point-and-shoot cameras use this technique.  Pocket cameras that use the rear LCD to preview the picture are sometimes set up this way and hence have no mechanical shutter at all.   Realizing that some cameras have all-electronic shutters while others have mechanical shutters, it's obvious that there are pros and cons to both designs.

Sensor Types

Interline Transfer

Cameras, typically smaller point-and-shoot cameras, that use no mechanical shutters typically use an interline transfer sensor.  An interline transfer sensor dedicates a portion of each pixel to store the charge for that pixel.  The added electronics necessary to be able to store the charge for each pixel reduces the fill factor of the pixel, in turn reducing it's ability to capture light since a portion of each pixel is not light sensitive.  Microlenses can be used to compensate but they are not 100% efficient and they can add expense to the design.  Interline transfer sensor's typically have higher noise levels and lower sensitivity than the full frame sensor's used in high end digital SLR's.  One obvious benefit is that this design eliminates the need for a potentially bulky mechanical shutter and can turn a purse size camera into a shirt pocket camera.

Full Frame

Digital cameras that use a mechanical shutter typically use a type of sensor called a full frame sensor.  Unlike the interline transfer sensor (above), the full frame sensor has no circuitry on the pixel to store the charge that builds up as light contacts the array.  Cameras that use a mechanical shutter typically bleed off any residual electrical charge while the shutter is closed, open the shutter, and then close the shutter.  Once the mechanical shutter is closed, circuitry is then used to shift the charge from each pixel into a storage area.  Since the pixels on the sensor remain "live" during readout, if the shutter remained open, light would continue to alter the charge accumulated by each pixel during the shifting operation which could result in blur or ghosting.

Mechanical shutters: the bottom line

In layman's terms, a mechanical shutter is used to control how long the pixels on an image sensor collect light.  A simple mechanical shutter can be used to turn the entire sensor array on/off during the exposure.  This eliminates the need for added electronics at each pixel location that would be used to turn on/off the pixel and store the charge (accumulated light).  By using a mechanical shutter, a simpler, less expensive, and more efficient sensor can be used: one that has a higher fill factor (uses more of each pixel to actually capture light).  Of course, nothing is ever cut and dried.  Some cameras use both a mechanical and an electronic shutter!  In these cases, the electronic shutter is used to supplement the mechanical shutter by providing features like a faster flash sync speed where mechanical shutters are just not fast/accurate enough.  Most digital SLR cameras that use a mechanical shutter, however, use the mechanical shutter to control the amount of charge accumulated on the sensor as this simple mechanical device can be used to simplify the circuitry on the sensor itself thereby generally improving image quality and reducing noise.

Summary

This article is designed to answer the question of why a digital camera, admittedly a "solid state" device that shouldn't logically need any moving parts other than a focus mechanism would need a mechanical shutter.  The answer, on the surface, turns out to be relatively simple and I hope I've answered the question so that most people can grasp the concept.

Mike Chaney

The Megapixel Masquerade

Background

Imagine a world where a camera can be dubbed "14 megapixel" when it has 4.6 million pixels on its imaging sensor while at the same time, another camera  can be dubbed "10 megapixel" when it has no pixels at all on its imaging sensor.  Sound like a strange world?  Maybe, but it's the world we live in today!  Evolving technologies are making it more difficult to define exactly what is meant by the term "megapixel" and is blurring camera specifications to the point that many people no longer know how to compare cameras by the specs alone.  In this article, I will try to explain how manufacturers come up with their marketing regarding the term "megapixels".

Pixel: a definition

Wikipedia defines a picture element, or pixel, as "the smallest complete sample of an image".  Others use similar terminology such as "the smallest discrete component of an image".  The key here is that we are talking about the smallest element in an image: that is, the final picture or photograph.  Obviously, a digital photograph is made up of millions of tiny points of light, each of which can have its own unique color and brightness.  When these points of light are displayed next to one another and viewed from a distance, the individual points of light fade together and we see what appears to be a smooth, continuous image.  There are various ways to represent color and brightness for each point of light or pixel in the image, but the most common is to assign each pixel its own set of red, green, and blue brightness values since you can reproduce a particular color by combining red, green, and blue intensities.  A pixel then, must have all three (red, green, and blue) components to be a complete sample of the final image.

Sensor photosites and pixels

Ever since images from digital cameras broke the one million pixel boundary more than a decade ago, the term "megapixel" has been used to describe resolution.  Using this term, buyers could get an idea about how large they could print, how much leeway they would have to crop images, and so on.  While a "10 megapixel" claim is accurate with respect to how many pixels are in the final (developed) image, somewhere along the way, the megapixel moniker has gotten confused with "camera resolution".  A typical camera claimed to be a 10 megapixel digital camera may produce 10 megapixel images, but by definition, the camera itself (the sensor) does not contain 10 million pixels.  Far from it in fact!  This "10 megapixel digital camera" actually contains no pixels whatsoever on its sensor.  Instead, the sensor is a conglomerate of 5 million green photosites, 2.5 million red photosites, and 2.5 million blue photosites.  Sophisticated software takes information from these 10 million individual samples of red, green, OR blue at each location in order to predict the missing two color channels at each pixel in the final image.  Since a pixel is defined as a complete picture element, a typical digital camera cannot be defined as a "10 megapixel camera" even if it produces a 10 megapixel final image because two thirds (67%) of that 10 megapixel final image is "predicted" rather than actual data.  For the camera itself to be called 10 megapixels, it must have 10 million pixels on the sensor, each of which is able to represent complete information without borrowing information from neighbors.

Enter Full Color Capture

For about a decade, none of this pixel definition nit-picking mattered because all cameras were roughly the same.  They all captured only one of the three red, green, or blue colors at each location on the sensor and they all predicted the missing two colors by looking at neighboring locations on the sensor and predicting.  The fact that your 10 million pixel image didn't come from a 10 million pixel camera didn't matter because everyone was compared on a level playing field.  When Sigma introduced the first consumer full capture camera (the SD9) in 2002, they were faced with a dilemma.  Should they call it a 3.5 megapixel camera because it delivers 3.5 million pixel final images, or should they call it 10 megapixels since it captures all three red, green, and blue color primaries at each location on the sensor?  Technically (by the definition of a pixel), they should label it as a 3.5 megapixel camera but its competition at the time were cameras dubbed as 6 megapixels even though they were not really 6 megapixel cameras.  Now that technology was changing, the "fuzzy" definition of megapixel that had worked for years suddenly broke down.  People started picking sides and arguing apples versus oranges.

Fast forward to 2007 and the same problem exists today.  Sigma's updated SD14 produces a 4.6 megapixel final image from 4.6 million sensor pixels.  Once again, Sigma was faced with how to label their product since the competition was calling their cameras 8 and 10 megapixel yet those cameras recorded no true pixels at all and the final 8 or 10 megapixel image had to be "derived" using a lot of educated guessing (read complex predictive analysis).  Had Sigma called their SD14 a 4.6 megapixel camera, most consumers wouldn't realize that since the camera captures full color, its final images are comparable to images from typical (non full color) 10 megapixel cameras.  They chose instead to take the "high road" and label it a 14 megapixel camera figuring that if the rest of the industry can claim 10 megapixels when only one third of each pixel is real data, they can claim 14 megapixels when they are capturing all three primary colors (4.6 x 3).  In reality, Sigma marketing was fighting misleading terminology with more misleading terminology.   They likely felt they needed to because it was easier than reeducating the masses by writing an article like this and then hoping everyone reads it.  The phrase "damned if you do, damned if you don't" comes to mind here.

Does it Matter?

It's interesting that some (both online and hard copy) publications can claim that calling a 4.6 megapixel full capture camera 14 megapixels is hype when no one complains that a camera advertised as 10 megapixels can't deliver 10 megapixels of real image information.  What's the real hype here: the fact that the SD14 is really 4.6 megapixels and not 14, or the fact that a typical camera labelled 10 megapixel really only captures one third of the information at each pixel?  The truth here is that sometimes you have to read the fine print.  When comparing single color capture cameras with full color capture cameras, just keep in mind that megapixel ratings really cannot be compared directly.  Both technologies work and one is not necessarily better than the other for all things, but when comparing megapixel numbers on paper, it's beneficial to note that the term "megapixel" is used rather loosely in this industry by both camps: the typical single color capture camp and the full color capture camp, i.e. Foveon/Sigma.  Due to the filtering and reconstruction involved in creating an image from a typical single color capture camera, it can resolve less detail per final-image-pixel than a full color capture camera like a Sigma SD14.  How much will depend on the image, but a decent rule of thumb is that full color capture cameras like the SD14 compare nicely to cameras with about twice as many pixels in the final image.  That is, the 4.6 megapixel SD14 can resolve detail comparable to a typical (single color capture) camera rated at about 9.2 megapixels.  I admit it's a bit silly to try to explain "fuzzy" logic with even more "fuzzy" logic but sometimes it's necessary unless you expect all your readers to have engineering or computer degrees.  :-)  If you want to read (and see) more about how complicated it can get comparing single color capture to full color capture, read my article on the SD14 versus Canon 5D where I take a look at some of the intricacies involved in comparing typical single color capture cameras to full color capture cameras.

The Eyeball Argument

Some reviewers screaming "hype" on the 14 megapixel designation of the Sigma SD14 argue that normal single color capture cameras can actually approach their rated resolution even when only one color per pixel is captured by the sensor.  I've seen claims that cameras rated at 10 megapixels can approach 10 megapixels of true resolution especially when capturing black and white detail.  While the algorithms designed to create a full color image from one-color-per-pixel sensors are actually pretty good at what they do especially on black and white detail, the edge blurring needed in order to make single color capture work properly holds them back from their upper limit potential.  Single color capture really starts to fall short (of rated resolution) when capturing highly detailed colorful subjects where the red, green, or blue locations on the sensor start to contribute less information than they would in a B/W scene such as a resolution chart.   I've also heard the argument that single color capture cameras, particularly those with the Bayer RGBG design, try to replicate how the human eye works, giving more resolution to green and less to blue and red, so that design is actually better as a result.  Such arguments are absurd, however, when you realize that replicating the deficiencies of the human eye is not a benefit but rather a necessity for single color capture!  The goal of any imaging device should be to produce the highest quality photographs possible and reproducing the most accurate information for each pixel is how we accomplish that task.  This is how, resolution-wise,  full color capture cameras like the SD14 can compare nicely to single color capture cameras with much higher final image resolution.  All this just goes to show that single and full color capture are not comparable on paper no matter what arguments are used to try to rationalize the comparison.

Summary

Don't be another victim in the megapixel wars.  Arm yourself with a little knowledge and you won't have to take the manufacturer's word for it when trying to compare (especially differing) technologies.  There's much more to buying a camera than just megapixels, of course, but if you like to look at specs, maybe this article will help a bit with understanding some of the claims made by manufacturers today with regard to megapixels and resolution.

Mike Chaney

Brightness, Contrast, Saturation, and Sharpness

Background

At first glance, it might seem that doing an article on the four most common image controls would be a waste of time.  After all, brightness, contrast, saturation, and sharpness are often thought to be the simplest controls as they've been around as long as the color TV.  People often overlook the fact that all four are related, however, and changing any one of them can change the other three.  Do you know how they are related and how you are changing the balance of brightness, contrast, saturation, and sharpness by only changing one of the three parameters?  Let's take a look.

Brightness

Brightness is generally thought to be the simplest in concept.  Just make the image brighter or darker by a specified amount, right?  First we must distinguish between true brightness and something else called "gamma".  Increasing gamma by moving a mid-tone slider on a histogram is not the same as increasing brightness.  Increasing Gamma/mid-tones can make an image look brighter, but it is non-linear in that it only increases brightness of the shadows and mid-tones in an image without affecting the highlights.  Traditional brightness on the other hand, simply brightens the entire image from the shadows to the highlights equally.  Let's see what happens when we add some brightness to an image.  The following test image is designed to bring out some of the effects we will refer to in this article.

Fig 1: Increase Brightness

In figure 1 above, we have increased brightness on the right half of both the B/W and color images.  In this case, we didn't increase brightness enough to clip the highlights (brightest colors) so we've only affected brightness here. 

Fig 2: Extreme Brightness

If we had made a more drastic change such as the one shown in figure 2 where we added even more brightness, we may have clipped the white/red spokes in the wheel which would have affected contrast, saturation, and sharpness!  In the extreme case shown in figure 2 above, we have added so much brightness that the shadows have "caught up" to the highlights because they are already as bright as they can get.  Now we have reduced saturation, reduced contrast, and reduced sharpness as a result.  The same effect can be seen if we had reduced brightness to the point that the shadows had nowhere else to go and the highlights started catching up to the shadows.  Depending on how close your shadows/highlights are to their endpoints already, you don't need an extreme change in brightness to affect the other parameters either.  When increasing brightness, you may find that you lose some contrast on the brightest details in the image while the rest of the image has the same contrast as before.  Again, this is due to the clipping that is caused in the highlights.

Contrast

Contrast is defined as the separation between the darkest and brightest areas of the image.  Increase contrast and you increase the separation between dark and bright, making shadows darker and highlights brighter.  Decrease contrast and you bring the shadows up and the highlights down to make them closer to one another.  Adding contrast usually adds "pop" and makes an image look more vibrant while decreasing contrast can make an image look duller.  Here is an example where we add some contrast.

Fig 3: Increase Contrast

In figure 3, we have added contrast to the right half of both images.  As you can see, the white/red spokes have gotten brighter while the background has gotten darker.  This causes the image to look more defined.  By making the highlights brighter, however, we've also increased the brightness of the spokes, causing the image to appear brighter since the spokes are the main focus of the image.  On the red image, increasing the brightness of the spokes has also increase saturation (defined below).  Finally, sharpness has also been increased on both images (also defined below).  Here, we have increased brightness, contrast, saturation, and sharpness simply by adding contrast!  Note that not all areas of the image will be affected equally and a lot depends on the content of the image itself.  Saturation effects, for example, will be less noticeable in images that don't show bright colors because there is very little saturation to begin with.  As an extreme example, take a look at the B/W image above.  Since B/W images have zero saturation by definition, changing contrast cannot change saturation in B/W (gray) areas of your image.

Saturation

Saturation is similar to contrast, however instead of increasing the separation between shadows and highlights, we increase the separation between colors.  An example showing increased saturation would show the same effect as figure 3 above for the red image but the B/W image would not change at all because B/W or gray detail has no saturation.  As a result, an increase in saturation results in an increase in contrast, brightness, and sharpness on the red image as in figure 3 and no change to the B/W image.  Again, a change in saturation normally has a more noticeable effect on vibrant colors and less on dull colors or colors that are almost neutral.  This is because to change saturation, there must be some color saturation to work with in the first place.

Sharpness

Sharpness can be defined as edge contrast, that is, the contrast along edges in a photo.  When we increase sharpness, we increase the contrast only along/near edges in the photo while leaving smooth areas of the image alone.  Let's take a look at an example with increased sharpness.

Fig 4: Increase Sharpness

The right half of the above two images has been sharpened using unsharp mask.  By only sharpening the edges, we've actually created several different effects in the above image.  Near the outer edge of the spokes, where the spokes are thicker, they simply look sharper without looking brighter or more contrasty.  As we approach the center of the wheel, however, where the spokes get very thin, our edge contrast enhancement has actually caused the center of the wheel to get brighter, more contrasty, and more saturated (on the red photo).  This is due to the fact that most of the data near the center is edge data so the effect increases in that area.  Here, we see that increasing sharpness can cause the appearance of increase saturation, contrast, and brightness in areas of the image that contain fine detail where other areas (areas with broader detail) seem less affected except for the added sharpness.

Different effects for different parts of an image

The overall effect of brightness, contrast, saturation, and sharpness will vary depending on the content in each photo.  Consider increasing contrast as an example.  Increasing contrast makes shadows darker and highlights brighter.  If we increase contrast on an image where most of the detail in the photo is very bright, say an overexposed sunset, we may actually end up with less contrast!  Why?  Because there are no (or minimal) shadows in the photo so separating the shadows and highlights in an image that only contains highlights will just compress the highlights, making them less contrasty.  Similarly, taking a soft focus shot and increasing saturation may cause bright/vivid colors to appear sharper than gray or near gray detail and that may cause an unwanted change in overall balance of the photo.  As an example, increasing saturation on a shot of a cricket sitting on a red rose petal may increase the sharpness of the red rose petal, taking focus off the less colorful subject (the cricket) because it will be less affected by the change in saturation.  The end result may be that the rose petal now looks sharper than the cricket, making the cricket appear to be out of focus, all because you increased saturation.  Being able to control these linked effects when using simple controls like brightness, contrast, saturation, and sharpness is a bit of an art, but understanding why we sometimes get unexpected results is half the battle!

Summary

While brightness, contrast, saturation, and sharpness may appear to be the simplest of image controls on the surface and may appear to be mutually exclusive controls, they are related and intertwined in such a way that changing any one of them can create quite complex effects in your photos.  Understanding how they are related can be a big step in understanding how to use them and more importantly when to use them.  Before adding or reducing brightness, contrast, saturation, or sharpness, think about this article and ask yourself what you are really trying to accomplish.  Hopefully this article will help you pick the right control or the right situation.

Mike Chaney