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Author Topic: January 2009: dSLR Video  (Read 17898 times)
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« on: May 27, 2009, 03:29:27 PM »

dSLR Video


A new trend is beginning to emerge in the world of dSLR cameras: the ability to shoot high definition video.  Enabling video on dSLR cameras is more than just a bragging right to include a feature often found in inexpensive pocket cameras.  It is starting to change the landscape of videography by bringing a professional film look within reach of consumers.  Let's take a look at the state of video with respect to dSLR cameras right now and see what all the hype is about.


Getting a dSLR to capture video

Let's face it, the dSLR until recently just hasn't been designed to capture video.  Both the mechanical shutter and the way that the data is read off the sensor are not conducive to capturing video so some changes were necessary to get the job done.  At a minimum, the shutter has to be designed to stay open for long periods of time and the mirror must remain in the up position for long periods of time without damage to the camera.  The same goes for the sensor itself: it must be designed to withstand constant operation at 30 frames per second.  In addition, a "live view" mode must make the rear LCD active during shooting, something not normally required on a dSLR due to the through-the-lens view available via the viewfinder.  In-camera processing power must also be robust enough to handle the data acquisition and video encoding.  Ideally, the camera should have a "frame read" type data acquisition from the sensor that can read the data on the entire sensor at the same instant so that an entire frame of video results in a true snapshot of the image.  Also, in an ideal world, the camera should have autofocus and the ability to change things like aperture in real time.  dSLR video currently meets some of these standards, but not all.


That film look

As of this writing, the two most notable entries in the dSLR HD video arena are the Nikon D90 and the Canon EOS 5D Mark II.  While both of these cameras can produce beautiful film-like video, there are some indications that Nikon and Canon are just testing the waters with these ground breaking cameras.  While they've produced cameras that can capture the shallow depth of field of "big screen" equipment costing ten times what these dSLR's cost or more, they lack some essential features that would make them more usable as a main stream video camera.  That film-like look and feel are the allure of the video capable dSLR.  When you see typical videos shot with a handheld camcorder, the depth of field is so deep that objects up close are just as in focus as objects in the distance, giving the movie a distinctly video feel. 

The larger sensor and shallow depth of field of the dSLR gives movies a more film-like appeal by allowing you to keep your subject in focus while blurring the background for a softer, more cinematic appearance.  Even if you don't know depth-of-field, apertures, or sensor sizes, when you watch a dSLR movie, it just feels cinematic compared to the video look of a camcorder.  In layman's terms, a dSLR movie often looks like something you'd see in a theater while a camcorder movie may look more like something your uncle shot in his back yard.  The dSLR's large sensor also gives it a low light advantage and shooting dSLR movies in low light is likely to be unrivaled by any handheld camcorder.


It's a dSLR, not a point-and-shoot

So far, everything sounds great.  Ready to go buy a D90 or a 5D Mark II to replace your HD camcorder?  Not so fast!  As the dSLR is just starting to get its feet wet in video, there are currently some limitations that make your average HD camcorder a more sensible buy for the average Joe.  So far, the manufacturers have not addressed all the technical details needed to make the dSLR a good camcorder for the masses.  Some details are subtle and are of little concern to most people, like the "video jello" effect seen on the D90 and 5D Mark II that causes objects to "warp" if the camera is panned very quickly from side to side.  The effect is caused by the rolling shutter: the D90 and 5D Mark II use a rolling shutter that captures progressive data off the sensor rather than grabbing the entire frame at once, hence the top of the frame is captured a fraction of a second earlier than the bottom of the frame.  Other issues are less subtle like lack of any real auto focus during video capture.  With the mirror up, the normal auto-focus path that the camera uses is blocked so the only autofocus mechanism is a slow and clunky contrast based system that you'll likely not want to use during video recording.  Sound quality is also not quite up to par with your standard HD camcorder, but the 5D Mark II does offer the ability to add an external mic.


Buying into dSLR video: is now the time?

I have no doubt that the issues that currently limit dSLR video capabilities will be addressed in months/years to come.  Future models are likely to solve the auto focus problem, add during-capture aperture adjustment, fix the video jello effect, and break the 12 minute clip length limit found on the 5D Mark II.  Unless you are someone in the business of creating short promotional or professional videos, I suspect you'd be disappointed if you are buying a D90 or 5D Mark II just for video.  Those cameras simply lack some of the features that the average consumer looks for in a video recording device such as quick autofocus, 10x smooth zooms, video-friendly image stabilization, and portability.  The bottom line is, if you're into creative cinematography and need a device to do work where larger equipment is normally needed, dSLR video may fit the bill.  If you are buying a dSLR camera to be a camcorder to use at soccer games, the family picnic, or a school play, you may be better off with an HD camcorder.  There are some nice HD camcorders that can do true 1080p video like the Canon HF100, so you have other options for sure.


Getting that film-like appeal from an HD camcorder

Yes, it can be done... well, almost.  :-)  1080p HD camcorders can produce video as clean and clear as a dSLR, save for one thing: that shallow depth of field.  One nice thing about using a dSLR for video is that you can easily have your subject in focus and then manually shift focus to blur your subject and bring something in the background into focus instead.  This focus shift is very appealing as it shifts the subject material without moving the camera or the subject.  Imagine a video showing a pilot talking about his stunt plane which is behind him, and the focus shifts form the pilot to the plane in the background.  Such focus shifts are more difficult with a camcorder for two reasons: (1) the camcorder typically will have such deep depth of field that both the pilot and plane are likely to be in focus at the same time to begin with and (2) the camcorder will typically focus on whatever is in the center of the frame.

Getting an HD camcorder to do the same thing is more difficult than using a dSLR with its inherent shallow depth of field and easy-to-use manual focus.  First, you have to set the HD camcorder to aperture priority mode and choose the widest aperture possible to reduce depth of field.  In doing so, if you are shooting an outdoor or other bright scene, you may have to use a neutral density filter to reduce exposure because the camcorder may not be able to expose properly with the aperture open all the way.  In addition, due to the smaller sensor size, you'll likely have to back up a little and zoom in on your subject to reduce depth of field even further.  Doing so will alter the apparent distance between the subject and the background.  In the above example, backing up and zooming in will make the subject look like he is closer to the plane than he actually is.  Finally, you have to put the camcorder into manual focus mode and shift the focus from the pilot to his plane.  Simply put, it's more difficult to set up the shot but with some compromises, you can do shallow depth of field focus shifting with an HD camcorder.  Here's an example using the Canon HF100 HD camcorder:

Shot with shallow DOF showing the foreground

Focus is shifted slowly to show the background

In the above shot, the video shows the Spanish moss in the foreground and slowly shifts to show the berries on the tree in the distance.  So it is possible to emulate shallow depth of field shots similar to the nice online examples from the dSLR's but if you know what to look for, there are some obvious compromises.  The most obvious is that you can't achieve the same shallow depth of field at wide angle so your shallow depth of field shots on a camcorder will be limited to relatively powerful telephoto zooms.



dSLR video is just starting to change the world of consumer HD video.  With their larger sensors and shallow depth of field, dSLR's can produce cinematic video unrivaled by any handheld camcorder.  That said, dSLR's have some serious limitations with regard to video capture if you are thinking of replacing your camcorder with your video capable dSLR.  I believe video capable dSLR's will eventually be to video what they are to still photography, but it may be wise to wait for the second generation if you want something that can produce cinematic video while providing the ease of use of a camcorder.  The next few months should be interesting as I believe the waters have been tested and now that people can see what is possible with dSLR video, the second generation can't be far off in the future!


Mike Chaney

« Reply #1 on: July 04, 2009, 07:27:36 AM »

Thanks to the writer,I like this site, I hope that it will works in the future.

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