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DPChallenge Forums >> Hardware and Software >> Unsharp Mask
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 09/14/2005 11:23:50 AM · #1
When you use this tool, what do you usually set the Radius and Threshold to?

June
 09/14/2005 11:31:08 AM · #2
Depends on the size of your image and the complexity of edges. If you are working on an image that is say 800 x 600, I would suggest starting at the following vlaues: 140, 0.4, 0.

Good luck.
 09/14/2005 11:36:25 AM · #3
Originally posted by tcmartin:
Depends on the size of your image and the complexity of edges. If you are working on an image that is say 800 x 600, I would suggest starting at the following vlaues: 140, 0.4, 0.

Good luck.


I normally work with images straight form the camera so whatever size the 20D and the 300D images are. I've normally have the radius set at 1px and I've sharpened at 75% but sometimes have gone to 100%.

June
 09/14/2005 11:43:19 AM · #4
Canon's recommendation for sharpening images from their DSLRs is amt=300, radius=0.3, threshold=0. that assumes that no previous ssharpening was applied, including in RAW conversion (most RAW converters do apply some gentle sharpening unless you turn it off.
I recommend amount=150, radius=0.3, threshold=3. The reason for the non-zero threshold is that it avoids emphasizing noise. For very noisy images, it might be necessary to up it a bit, and for very clean images, 1 or 2 might work just as well. The difference is subtle, but it is there.
If the lens is not auite so sharp, then the raadus can be increased slightly, but I almost never go beyond 0.5
If one pass still looks a little soft, try a double pass. Two passes at a lower setting seems to give a better result than one pass at a high setting.
 09/14/2005 11:52:12 AM · #5
Originally posted by kirbic:
Canon's recommendation for sharpening images from their DSLRs is amt=300, radius=0.3, threshold=0. that assumes that no previous ssharpening was applied, including in RAW conversion (most RAW converters do apply some gentle sharpening unless you turn it off.
I recommend amount=150, radius=0.3, threshold=3. The reason for the non-zero threshold is that it avoids emphasizing noise. For very noisy images, it might be necessary to up it a bit, and for very clean images, 1 or 2 might work just as well. The difference is subtle, but it is there.
If the lens is not auite so sharp, then the raadus can be increased slightly, but I almost never go beyond 0.5
If one pass still looks a little soft, try a double pass. Two passes at a lower setting seems to give a better result than one pass at a high setting.


Excellent info. Thx kirbic.
 09/14/2005 11:54:33 AM · #6
Originally posted by kirbic:
Canon's recommendation for sharpening images from their DSLRs is amt=300, radius=0.3, threshold=0. that assumes that no previous ssharpening was applied, including in RAW conversion (most RAW converters do apply some gentle sharpening unless you turn it off.
I recommend amount=150, radius=0.3, threshold=3. The reason for the non-zero threshold is that it avoids emphasizing noise. For very noisy images, it might be necessary to up it a bit, and for very clean images, 1 or 2 might work just as well. The difference is subtle, but it is there.
If the lens is not auite so sharp, then the raadus can be increased slightly, but I almost never go beyond 0.5
If one pass still looks a little soft, try a double pass. Two passes at a lower setting seems to give a better result than one pass at a high setting.


Good info as always, thanks!
 09/14/2005 12:03:36 PM · #7
I work with files straight from the camera and it does depend. However, I start out with:

File Size: w/1152 pix h/1728 px better terms; w/16 inch and h/24 inches. Camera setting Jpeg/small/smooth. (This is based on with general shooting needs)

Unsharp Mask settings:

Amount= 100%, then adjust backwards. You shouldn't have to go over 100%, if so, it's to blurry to save and the photo scraped and need a re-shoot. This is just me. However, you can adjust the Radius to compensate from needing to go over 100% in Amount.

Radius: I use 3.0 and it seems to work VERY well in every photo I adjust. However, I wouldn't go over 5.0 when compensation the Amount. Again, the photo may need to be scraped and a re-shoot.

Threshold: 1 px. I never ever move this around.

So,

Amount: 35%-100%
Radios 3.0
Threshold: 1

Hope you find success in sharpening up your photos.

09/14/2005 12:12:57 PM · #8
I usually do 250+ % at .2 and 0 or... 130+ % at .3 and 0. It depends on the picture but I find that pictures look oversharpened and get artifacts if you push a small (entry sized) picture past 175% and .3 or anything higher than .3 radius.
 09/14/2005 12:13:22 PM · #9
I also use a technique usually called "contrast-enhancing USM" which uses some wacky values, for example:
Amt: 16%
Dia: 64%
TH: 0

I'll often then apply more typical values, such as (for DPC entry-sized files)
Amt: 88%
Dia: 0.8
TH: 5

For larger print files, I'll usually raise the diameter setting a bit, to maybe 1.3, and if there're a lot of smooth tones I'll raise the TH setting to 7 to avoid banding. I also find a better result with two "light" applications of the filter than with one "heavy" one.

I have some examples of sharpening effects in this pBase gallery.
 09/14/2005 12:26:23 PM · #10
[quote=GeneralE] I also use a technique usually called "contrast-enhancing USM" which uses some wacky values, for example:
Amt: 16%
Dia: 64%
TH: 0
........."

Hey, this made me go smile...nice setting........
 09/14/2005 12:36:51 PM · #11
I tend to use a variety of techniques.

for DPC size images:

Amt 66%, Dia 1.6, TH 0

is about the best single pass method I have found. Applying this in the luminosity channel can help avoid haloing (either switch modes, or apply then fade to 100% on luminosity).

For print images, I tend to double the diameter:

Amt 66%, Dia 3.2, TH 0

works well. Increasing TH can avoid sharpening artefacts on noise.

Interesting results can be had from trying

Amt 250%, Dia 0.1, TH 0

and

Amount 30%, Dia 140, TH 0

These have a more significant effect on contrast (a good reason to always apply adjustments in adjustment layers, so that they can be reduced post sharpening).

You can sometimes reduce haloing by apply a filter at half strength twice, once with 100% fade set to darken, then 100% fade set to lighten (or vice versa, I forget).

Something that I am slowly getting to grips with is using sharpening properly with reference to the desired print resolution.

I imagine (maybe someone will correct me?) that a properly sharpened image at full size when viewed on screen will be improperly sharpened when printed if the printer resolution does not accord with the full size image resolution. By way of example:

my local printer prints at 400dpi. Say I have an image with resolution 4800 x 3200. I want a print at 6"x4". The image is properly sharp at 4800x3200 when viewed at 100% on my monitor. However, when being printed, the printer must (I presume) downscale my image to 2400x1600 (6"x4" at 400dpi). The 2400x1600 image will, I guess, be oversharpened. The 6x4 print will look a bit rubbish as a consequence.

I intend to try it, but I presume that what I ought to do is:

1. select print for printing
2. decide what size to print it at
3. crop for correct aspect ratio
4. resize image with bicubic algorithm etc so that the screen resolution matches the desired print resolution
5. sharpen the image.

[I have been missing out step 4, and have had xome very mixed results from prints]

For some prints that will mean upscaling, and for others downscaling, depending on the crop and the print size. If I want to print the same image at different sizes, I will have to make multiple copies, each manipulated to the correct size and print size. If I go to a different printer who has, say, a 300dpi photo printer, I ought to redo my post processing to ensure proper sharpening etc!

These appear to me to be the frustrations of digital.

Message edited by author 2005-09-14 12:41:51.
 09/14/2005 12:46:11 PM · #12
Apologies for my lack of concision.
 09/14/2005 12:58:24 PM · #13
For print files, you also have to consider the "native" resolution of the printer, and the way the image is being created.

A laser spot exposing silver-halide photographic paper has different requirements than a 720 dpi inkjet printer, which is different from a 1200 dpi color laser, which is different from a 2400 dpi imagesetter making a 150 LPI halftone screen for magazine printing.

Your printer may well "resize" rather than resample your image, a process more akin to using an optical enlarger with film. It will "probably" send the full data to the printer, giving you a 6x4 @ 800 dpi.

But your general plan of manually resizing/resampling images for specific output devices is a sound one. If you really get into it, you'll probably want to attach separate printer profiles to those files as well.
 09/14/2005 02:15:53 PM · #14
I just realized I had absolutely no idea how the unsharp mask really worked, and I test out some of your guys settings, and seriously looked about ten times better than what I do.

But I'm curious because most of the setting you guys gave are for a photo that's alredy been shrunken in size, so what do you do when you're editing with the large file?
 09/14/2005 02:20:42 PM · #15
Originally posted by movieman:
But I'm curious because most of the setting you guys gave are for a photo that's alredy been shrunken in size, so what do you do when you're editing with the large file?

I usually leave the Amt and TH settings alone, and moderately increase the diameter setting. I never work on really big files, so I've never had to go over about 1.3 for that.
 09/14/2005 07:30:05 PM · #16
Originally posted by GeneralE:
Originally posted by movieman:
But I'm curious because most of the setting you guys gave are for a photo that's alredy been shrunken in size, so what do you do when you're editing with the large file?

I usually leave the Amt and TH settings alone, and moderately increase the diameter setting. I never work on really big files, so I've never had to go over about 1.3 for that.


Awesome, thanks, I'll give that a go.
 09/14/2005 07:37:50 PM · #17
I use something similar to George Lepp's method. Which is...

50
1
3

09/14/2005 07:49:17 PM · #18
For first pass on images converted to tiff from RAW with in camera sharpness set to Normal: 125%, .7 - 1 Radius, o Threshold. Depends on the situation. Sometimes if you're not careful you can get jaggies caused by overshapening. Always sharpen while viewing at 100% to watch out for those things. After I the websize image I USM again with approx. half the radius of the first run.
 09/15/2005 11:41:11 AM · #19
Originally posted by GeneralE:
which is different from a 2400 dpi imagesetter making a 150 LPI halftone screen for magazine printing.


could be 200LPI @ 2400DPI..

Smart Sharpen is much better than USM :)
 09/15/2005 11:48:16 AM · #20
Originally posted by Bobster:
Originally posted by GeneralE:
which is different from a 2400 dpi imagesetter making a 150 LPI halftone screen for magazine printing.


could be 200LPI @ 2400DPI..

Smart Sharpen is much better than USM :)

Most magazines are still printing 150-175 LPI screens on web presses; we occasionally print a 200 LPI screen on our sheetfed presses. My imagesetter will actually go up to a 300 LPI screen at 3600 dpi, but we've rarely used it at that level -- it's incredibly slow.

I keep thinking I should create some custom filters with it -- custom graduated ND filters and such. I think that close to the lens, the halftone dots will defocus sufficiently.
 09/15/2005 12:22:56 PM · #21
The amount of sharpening should be limited on any single pass to no more than 10% of the long side pixel count. So the amount on a 2400pix image needs to be way lower on a 640pix image. Same with the other values. Absolute numbers in any technique are based on a specific pixel count that the person is assuming you have to work with.
 09/15/2005 12:25:19 PM · #22
Do you mean the "Amount" value or the "Diameter" value? Why would the "Amount" value relate to the absolute number of pixels present?
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