[argyllcms] Re: wtpt/chad in input V2 sRGB profiles from color.org

  • From: Roger Breton <graxx@xxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 03 Aug 2012 07:23:00 -0400

In my opinion, any profiles must encode their white point as D50, that's per 
the ICC specs.

If the encoded white point is actually D65, then it's not surprising that there 
is a color cast when using AbsCol. Provided the profile is not used in Adobe 
CreativeSuite since Adobe ignores the profile encoded white point to use D50 no 
matter what. Same with conversions.

I know Graeme has a lot to say about this issue... I wish I could trace his 
arguments better.

/ Roger 

-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx] On 
Behalf Of Alexey Blinov
Sent: August-03-12 1:44 AM
To: argyllcms
Subject: [argyllcms] wtpt/chad in input V2 sRGB profiles from color.org

May be question to a wrong place..

Could somebody (knowledgeable) comment on wtpt/chad tags in (the two) V2 sRGB 
profiles from color.org (http://www.color.org/srgbprofiles.xalter) ? More 
specifically:

They say they set wtpt=D50 to eliminate color cast when absolute colorimetric 
intent is used. To me it's vice versa: it introduces a yellow cast, when I set 
it as (sRGB) profile in GIMP.

{r,g,b}XYZ tag values (colorants) from those profiles coincide with those from 
Argyll's sRGB profile. However, iccgamut+viewgam show whitepoints around D50 
and D65 correspondingly for color.org and argyll profiles. So it looks like 
color.org assumes a transform using chad, making white point D65->D50. Why?

No issues with sRGB profile supplied with Argyll.


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