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Author Topic: Use of USM  (Read 10313 times)
Owen Glendower
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« on: September 01, 2011, 04:49:33 PM »

I still consider myself a novice at post-processing, including the use of USM, although TTS in QU has simplified my life.

However, this info from the Luminous Landscape site leads me to wonder if I've been too conservative when applying USM.  Would appreciate your thoughts on the rule of thumb described below.  Underlining is mine.  Bold is emphasis in the original.

Quote
...all files which have USM applied have halos, though obviously some more than others. Halos are caused by edge contrast differences, which is what USM does — enhance edge contrast (know in film days as "accutance"). The standard approach to applying the right amount of USM visually is to increase Radius and Amount in proportion for a particular image so that halos begin to be visible at 100% magnification. If one does this properly then at any normal print size they will be invisible. Too much and the image is oversharpened. Too little and the amount of sharpening will be inadequate.
...
Regrettably a lack of understanding of this topic is all too common. That's why we see people critiquing 100% enlargements of other people pictures online and making all kinds of unfounded deductions. Here's a statement to consider: Any digital image seen at 100% that is either from an in-camera JPG or from a RAW file which has had USM applied properly by the user will show halos. One therefore can not use 100% magnification images to form a reliable conclusion about real-world image quality.


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Fred A
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« Reply #1 on: September 01, 2011, 05:03:24 PM »

Quote
amount of USM visually is to increase Radius and Amount in proportion for a particular image so that halos begin to be visible at 100% magnification. If one does this properly then at any normal print size they will be invisible. Too much and the image is oversharpened. Too little and the amount of sharpening will be inadequate.


I just want to say, if the print has halos, it's over sharpened.

Also want to point out that the person who wrote that treatise has a point where the print might need more sharpening because there is a loss of sharpening between screen image and print.
But, simply put, Qimage Ultimate has a feature called Smart Sharpen which compensates for that mismatch of sharpening, and accounts for print size changes etc.
So I can go back to looking at my image on screen, and if I see halos, back off the radius setting until they disappear.

Fred
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Owen Glendower
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« Reply #2 on: September 01, 2011, 05:36:56 PM »

So I can go back to looking at my image on screen, and if I see halos, back off the radius setting until they disappear.
Fred

Yep, same here.  But I don't think that I've always applied USM to the point where halos are just visible when viewed at 100% magnification, as the writer recommends.  Will have to experiment and make a few test prints.  I remember a few cases where the image on screen looked a bit "crispy," but the print looked just right.

Appreciate your input.
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vsteffel
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« Reply #3 on: September 01, 2011, 06:19:20 PM »

I too am not strong in post processing techniques.  I agree that oversharpening can produce halos.  So, I've had to redo photoss.

However, I think that there are two other factors that could produce halos:
1) ghosting;
2) photographing an object that has the sun behind it.  Here's an example.
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Fred A
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« Reply #4 on: September 01, 2011, 07:29:46 PM »

Quote
But I don't think that I've always applied USM to the point where halos are just visible when viewed at 100% magnification, as the writer recommends.  Will have to experiment and make a few test prints.  I remember a few cases where the image on screen looked a bit "crispy," but the print looked just right.

I disagree with people that advocate processing images for the sake of processing, and then call that "Their work flow".
I have loads of images that are so very razor sharp that they do not need processing, and would suffer from adding anything, especially sharpening.
How can anyone write an article advocating adding sharpening to "all" images until....
I would not expect a doctor to prescribe medicine without seeing and examining his patient, as I would not expect a photo guru to prescribe adding Unsharp Mask to every image without inspecting the image first.
I live near the Gulf of Mexico. A large % of my pictures are mostly sky, water, and clouds, with a subject of people on a beach, birds, a boat, or no specified subject. All three, sky water and clouds making up the scene.
I surely do not want to sharpen sky, water or clouds for obvious reasons.
That's why I love my Qimage Ultimate with the ability to "accent" the boat or people or bird or lighthouse.... without touching the sky, clouds or water.

I see no way to lump anyone's images into a rule that advocates sharpening to the halo.

As for ghosting, I don't put that into the same basket with halos.
I have seen and even created ghosting by over use of other processing tools on an image with, as Mr. Steffel says, has the sun behind it and a sky background.
No Sharpening added at the time.
Nevertheless, he is correct in the thinking that processing is a tool to be used with prudence and care.  Not with wild abandon because someone wrote an article.

Fred
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Owen Glendower
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« Reply #5 on: September 02, 2011, 02:40:22 AM »

You raise a good point, Fred.  I don't live near a major body of water, as you do, but I nonetheless occasionally have the opportunity to shoot some "foggy morning" or "misty day" scenes.  Applying sharpening to these as a matter of course would be preposterous.  In one case, the scene turned out to be the only image I have ever printed where watercolor paper turned out to be the most appropriate medium.  Why in the world would I have applied any sharpening?

Of course, I'm sure that many people exclusively shooting jpegs with a good p&s digicam find no need to sharpen in post.  The default settings can produce snappier jpegs than a dslr out of the box.  That was certainly my experience when I compared jpegs from a Canon Powershot Pro1 to jpegs from a Nikon D5000 at the default settings.

I was reminded of this just the other day when a new acquaintance who exclusively uses a digital p&s was surprised when I told him that I sometimes applied sharpening in post.  That's because I apply none in camera, of course.

"The life so short, the craft so long to learn..."  Yeah, but the idea's to keep learning.  Thank heavens for these forums.
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Fred A
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« Reply #6 on: September 02, 2011, 09:42:43 AM »

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Of course, I'm sure that many people exclusively shooting jpegs with a good p&s digicam find no need to sharpen in post.  The default settings can produce snappier jpegs than a dslr out of the box.  That was certainly my experience when I compared jpegs from a Canon Powershot Pro1 to jpegs from a Nikon D5000 at the default settings.

That's just the point....
All RAW images are inherently soft/   Jpgs are processed in the camera with added amounts of sharpening, saturation, etc.
So now we think about what Q-Ultimate does as we open a fresh folder of Raw photos in Qimage.
We have already, by default, (See EDIT Preferences, Raw options) set a baseline of Unsharp Mask type sharpening.
This is set by the user by camera model usually.
We work from this baseline, deciding later.... if that image needs more sharpening.
If we find that every image, all the time, different lighting conditions, needs more sharpening, we can adjust the baseline.
See my snap attached.
Image #100 is the default that you use when you first get your Qimage Ultimate.

Image #097 is my setting that matches MY camera, and the lens I use most.
These settings are not critical nor coarse or impactful.
They are ballpark settings so you hardly see a change if you make a change.

Image #098 is showing you how you can have multiple presets that you can load with a click.
I have a preset for a 20 D and D 60 Canon, plus a 350D, and a Lumix G-1 (Not mine).

So you can see the multi faceted uses of USM on Raw images.
I have a Canon 17-40mm lens that I don't use often enough, that is so sharp, it is scary.
My default setting for USM is on the edge for that lens....
Lots of variables.
That's why I believe you can not make a blanket protocol of adding sharpening to every image after the fact.

Fred


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davidh
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« Reply #7 on: September 02, 2011, 04:41:57 PM »

There are many different ways to 'sharpen' an image and no single method is always the correct method!
Adding some contrast alone, can sometimes be enough.
If you really want to learn correct sharpening than I suggest this series of 6 Tutorials that I have found to be the most comprehensive on the net.Rons other and tuts videos aren't too bad either ;-) !!

http://www.ronbigelow.com/articles/sharpen1/sharpen1.htm

http://www.ronbigelow.com/articles/articles.htm


David
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Hening
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« Reply #8 on: September 15, 2011, 06:27:32 PM »

Thanks for that link, David!
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