[argyllcms] Re: Using BtoA1 table with rendering intent absolute
- From: Gerhard Fuernkranz <nospam456@xxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 07 Sep 2007 22:08:32 +0200
John Weissberg wrote:
> Can you supply details of which CAT we should use? Bradford? Von
> Kries? Another?
At least the ICC V4 spec assumes a wrong Von Kries transformation
(diagonal scaling in XYZ space) for the transformation between
illuminant and the media color under the illuminant, while the CAT
between the illuminant and the PCS illuminant (D50) is described by the
"chad" tag in the profile (the latter is an identity transformation
though, if the illuminant is already D50).
The V2 spec was not interpreted uniquely by profile vendors, so I would
not rely on a particular CAT being assumed by the profile. However, for
the small chromaticitly difference between D50 and paper white under
D50, the used CAT method will not make much difference anyway.
>
> Any reference to the actual formula would be appreciated?
http://color.org/icc_specs2.xalter
http://color.org/ICC1v42_2006-05.pdf
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