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DPChallenge Forums >> Hardware and Software >> Unsharp Mask in Gimp vs Photoshop
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Showing posts 1 - 14 of 14, (reverse)
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 10/26/2004 11:07:43 PM · #1
Does anyone know how the settings for USM in Gimp and Photoshop are different? Amount seems to function differently. In PS it is in %'s. In Gimp it is a number. How do they translate?
 10/28/2004 06:58:44 PM · #2
bump
 10/28/2004 08:23:55 PM · #3
As far as I know, it's just about multiplying...

An amount of 1.25 in GIMP = 125% in PS. Radius and threshold I think are the same.


10/28/2004 08:39:44 PM · #4
A trick I just learned that I'm applying in Gimp now:

Sharpening in LAB color space. A little bit of info here. Basically you decompose the RGB image to the LAB color space (luminosity - color_a - color_b), apply unsharp mask to ONLY the luminance layer, then compose the layers back to an RGB image.
(This is the process for Gimp 2.0/2.1 at least.)

The benefit that the color data is better preserved. It seems to provide nice results.
 10/28/2004 08:41:19 PM · #5
Oh yeah, Gimp 2.1.7 has a preview for the USM tool!! It's totally sweet. Quite a few other niceties too. It's a development version though, but seems stable. The 2.2 release shouldn't be too far away. :)
 10/28/2004 09:29:02 PM · #6
skylen, can you show an example of your Sharpening in LAB color space?
Thanks in advance.
Richard
 10/28/2004 10:32:35 PM · #7
thanks. I'll see how well all that works.
 10/28/2004 11:32:26 PM · #8
Originally posted by goodtempo:
skylen, can you show an example of your Sharpening in LAB color space?
Thanks in advance.
Richard


Here's a quick comparison. I did a test with an image, and sharpened it 2 different ways. (1) is just using the GIMP USM filter, radius 0.1 amount 1.50, threshold 0. (2) is the same except I did a decompose to LAB, applied the same USM, then recomposed to RGB.

Here is a 100% crop scaled up 300% so you can see the details better:
(1) (2)

If you look at the bench about 1/4 of the way down from the top of the image, you'll see much more 'color' introduced in (1), colors that didn't actually exist. It's much better in (2). Edges also seem a little better defined in (2).
 10/29/2004 09:57:35 AM · #9
Wow - that's almost imperceptible on my screen. I'm not sure it's obvious to me from those examples that more color was preserved. Edge definition dind't seem too much different to me either, but maybe it's caffeine defficiency on my part. There are many different sharpening techniques, and I'd imagine each has its pros and cons in different scenarios.

I'm anxious for GIMP 2.2 as I've heard rumours about introduction of color profiles in either 2.2 or 2.4. PS will be in trouble when GIMP / Linux supports profiles... If they get to that level of fine color control, chances are they'll have also introduced 16/24 bit image support as well. With 16 bit support and profiles, Photoshop's only remaining functional advantage will be the existing 3rd part plugins. Certainly not worth the price tag in my book, but it will be interesting to see what happens.
 10/29/2004 10:03:59 AM · #10
Thanks guys for covering this topic. I was myself unsure how Gimp's USM compares to Photoshop's.
 10/29/2004 10:48:53 AM · #11
Originally posted by cghubbell:
Wow - that's almost imperceptible on my screen. I'm not sure it's obvious to me from those examples that more color was preserved. Edge definition dind't seem too much different to me either, but maybe it's caffeine defficiency on my part. There are many different sharpening techniques, and I'd imagine each has its pros and cons in different scenarios.

I'm anxious for GIMP 2.2 as I've heard rumours about introduction of color profiles in either 2.2 or 2.4. PS will be in trouble when GIMP / Linux supports profiles... If they get to that level of fine color control, chances are they'll have also introduced 16/24 bit image support as well. With 16 bit support and profiles, Photoshop's only remaining functional advantage will be the existing 3rd part plugins. Certainly not worth the price tag in my book, but it will be interesting to see what happens.


When I have a chance, I'll make a page on my web site using mouseover to toggle between the two images. When I toggle between them in place, the difference is really obvious. It's less obvious when they're only side by side.

Don't forget adjustment layers as a Photoshop advantage though! They let you open a file, and modify settings like the curves you've applied, etc. This is a feature I really really want also.
 10/29/2004 11:26:38 AM · #12
I often percieve the GIMP development community as focusing on web graphics more than photography. Just looking at many of the filters and options, its obvious they favor something other than manipulating photographs.

I'm wondering if there's a way GIMP users from the photography world could become more vocal about needs... I'm all for the open source "pitch in" approach, but I'm not a graphics developer and haven't touched C code in years.

Just wondering what (if anything) can be done to advance those features in a productive way so we open source users can gain equal footing with Win/Mac. Any ideas?

I've got alaundry list of things I'd like to see enhanced in RAW handling via dcraw, but didn't have much luck getting responses from the developer (which I find unusual in the OS community in general).
 10/29/2004 01:37:44 PM · #13
Originally posted by skylen:
A trick I just learned that I'm applying in Gimp now:

Sharpening in LAB color space. A little bit of info here. Basically you decompose the RGB image to the LAB color space (luminosity - color_a - color_b), apply unsharp mask to ONLY the luminance layer, then compose the layers back to an RGB image.
(This is the process for Gimp 2.0/2.1 at least.)

The benefit that the color data is better preserved. It seems to provide nice results.


Paint Shop Pro 9 has a little check box that says 'luminance only'. If anyone has PSP9 they can save a few steps.
 10/30/2004 02:30:45 AM · #14
Originally posted by cghubbell:
I often percieve the GIMP development community as focusing on web graphics more than photography. Just looking at many of the filters and options, its obvious they favor something other than manipulating photographs.

I'm wondering if there's a way GIMP users from the photography world could become more vocal about needs... I'm all for the open source "pitch in" approach, but I'm not a graphics developer and haven't touched C code in years.

Just wondering what (if anything) can be done to advance those features in a productive way so we open source users can gain equal footing with Win/Mac. Any ideas?

I've got alaundry list of things I'd like to see enhanced in RAW handling via dcraw, but didn't have much luck getting responses from the developer (which I find unusual in the OS community in general).


What features are you looking for in dcraw or RawPhoto? I've been thinking about diving into that myself. The one thing I've thought of is that I'd like to have a curves tool in RawPhoto itself so I can do corrections and adjustments to the 16-bit data.
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