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Author Topic: Gamut warning question  (Read 3219 times)
PeterAit
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« on: January 21, 2009, 09:10:15 PM »
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Something is not working properly or at least not the way I think it should, and I hope someone can provide an explanation.

I have displayed a photo's colors in a 3-D graph in ColorThink Pro, along with the gamut of my printer/paper combination. Some of the image colors lie outside the gamut of the printer/paper. I then open the image in CS4, which has soft proof set up for the same printer/paper profile. When I view the gamut warning, I see nothing - no pixels are displayed as out-of-gamut (and it is set to bright pink so I won't miss anything). Shouldn't the colors that ColorThink shows as out of gamut be marked as such in PhotoShop?

Thanks in advance,

Peter
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Peter
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Damo77
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« Reply #1 on: January 21, 2009, 09:48:10 PM »
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I don't know anything about ColorThinkPro, but my guess is that it's mapping your photo's colour space's gamut, rather than the gamut of the actual photo itself.

What I'm saying is, your chosen colour space may be capable of very bright colours, but those colours don't actually exist in this photo.

I'm guessing ...
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Damien
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« Reply #2 on: January 22, 2009, 02:22:42 AM »
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Quote from: PeterAit
Something is not working properly or at least not the way I think it should, and I hope someone can provide an explanation.

I have displayed a photo's colors in a 3-D graph in ColorThink Pro, along with the gamut of my printer/paper combination. Some of the image colors lie outside the gamut of the printer/paper. I then open the image in CS4, which has soft proof set up for the same printer/paper profile. When I view the gamut warning, I see nothing - no pixels are displayed as out-of-gamut (and it is set to bright pink so I won't miss anything). Shouldn't the colors that ColorThink shows as out of gamut be marked as such in PhotoShop?

Thanks in advance,

Peter

Things like gamut, gamut boundaries and gamut warning are implemented somewhat differently in Photoshop and Colorthink.
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gianfini
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« Reply #3 on: January 22, 2009, 12:17:13 PM »
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I also found this strange behavior by PS. My guess is that PS maps image toward larger gamut at any L level. Usually colors out of printer gamut are in the darkest or lightest areas but same 'a' and 'b' combination might be in gamut at other L levels.

just my guess.

Indeed it would be great if the out of gamut warning would actually detect pixels outside output color space correctly...

g
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digitaldog
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« Reply #4 on: January 22, 2009, 02:52:51 PM »
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The old, legacy (ugly) gamut warning is of little usefulness these days. Prior to Photoshop 5 and ICC color management, the idea was to have you see the out of gamut colors, then desatruate them with the sponge tool. Now that ICC profiles can do this with far greater speed and precision, plus show you the soft proof, its questionable why this is even in the application.
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Andrew Rodney
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PeterAit
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« Reply #5 on: January 23, 2009, 01:41:53 PM »
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Quote from: digitaldog
The old, legacy (ugly) gamut warning is of little usefulness these days. Prior to Photoshop 5 and ICC color management, the idea was to have you see the out of gamut colors, then desatruate them with the sponge tool. Now that ICC profiles can do this with far greater speed and precision, plus show you the soft proof, its questionable why this is even in the application.

If it worked, it would be valuable to see where the out-of-gamut colors are located. Anyway, here's a response I got from Pat Herold at Chromix in response to my question (posted here with his permission):

It's been known around the industry for some time that Adobe's gamut warning feature is not entirely reliable. It tends to give false positives, or in other words tends to show that colors will be in gamut which actually are not. Adobe has not updated this function through many of the recent releases of the software. I suppose they just expect it to be used for what it is: A rough approximation of what's in gamut.


The best we have been able to determine is that Adobe's system works about the same as a 2D view of the image and profile. If you look at your image and profile in ColorThink's 2D mode you might find that most of your pixels fit within the 2D boundary outline. But we know that the 3D view tells the whole story. We often find that more saturated shadows areas fall outside of the actual profile gamut in that lower area or in the extreme highlights. Is that what you are seeing?


So, the bottom line is that the ColorThink graph should be showing you more accurately what is out of gamut, and that is why you have ColorThink!
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Peter
"Photographic technique is a means to an end, never the end itself."
View my photos at http://www.peteraitken.com
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