Re: MS Color Control Applet
Re: MS Color Control Applet
- Subject: Re: MS Color Control Applet
- From: Steve Upton <email@hidden>
- Date: Fri, 30 Jun 2006 17:41:51 -0700
At 11:10 AM -0500 6/27/06, Scott Campbell wrote:
>Hi Marco and Oliver,
>
>I just upgraded to ColorThink Pro. I also assumed Prophoto encompassed Adobe RGB. I just quickly viewed a 3D comparison of Adobe RGB 1998 and Prophoto RGB and found that Prophoto did "encompass" Adobe RGB 1998. I went back and looked at both in Colorthink 2.1.2 on my Mac, and Prophoto did not encompass Adobe RGB as Marco noted.
Hi All,
I wondered when this topic would come up....
To begin, there's some history and logic around this one. In the beginning of time I designed the gamut volume so that it would correspond directly to the measured data that built the profile. So if you graph target measurements with the resulting profile, the target colors match up with the profile volume quite nicely.
Cool, makes sense, expected behavior, etc.
When it came to graph monitor and working-space profiles I left ColorThink to behave the same way. What this means is that if the monitor profile has a non-D50 white point it maps to a non 100,0,0 white point in the graph as you described. All Lab graphing in ColorThink is in PCS-Lab which has a D50 white point.
While this could be argued to be the correct way to do things there are also arguments against it:
- to the "adapted eye" each monitor would appear to have a "white" white point and all colors would fall out relative to that white. So to the adapted eye the white points should line up.
- it turns out that any white point other than D50 in monitor profiles was not intended in v2 profiles and has been "outlawed" in v4 profiles. All colors are to be adapted to D50 and the white point should be D50 from now on.
- gamut comparisons should be done with the white points adapted in some manner. This will give a better indication of how two gamuts compare that when one of them has a shifted white point.
With this is mind it makes more sense to map all monitor gamuts to 100,0,0 which is how ColorThink Pro now plots and non-pro ColorThink will follow as well.
It is fair to say that either method could be used and their might be valid reasons for both. In canvassing many opinions and looking into an ICC v4 future it makes most sense to change the way things were done. I'm sure it will create some discussion along the way...
At 9:16 AM -0700 6/27/06, Marco Ugolini wrote:
>
>When comparing color spaces on a 3D graph, I think the correct way is to use the absolute colorimetric rendering intent (which is the way ColorThink does it), that is to say, *not* to adapt the white point, and certainly not to perform any black point compensation.
Ultimately what I decided to do was go with a hybrid approach. Because I really wanted the measurement data cloud to match up with the gamut volume for printers, I left print profiles graphing as absolute colorimetric by default. ColorThink Pro will recognize display/workingspace profiles that have non-D50 white points and graph them as relative colorimetric.
Because Pro is, well, 'pro' level, I also left the ability to change this behavior exposed to the user. So when a profile is graphed in Pro the default intent will be "device gamut" which determines the appropriate intent based on the above logic. You can also override this setting to graph D65 spaces offset, or pull print gamuts' white points up to 100,0,0 and so forth.
I hope this helps. Gamut graphing seems to be an area where there hasn't been a lot of research and discussion so sometimes we're forging ahead into new territory.
Regards,
Steve
________________________________________________________________________
o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX
o email@hidden 206.985.6837
o ColorGear ColorThink ColorValet ColorSmarts ProfileCentral
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