RE: Photoshop 6/7 problems with OptiCAL Monitor profiles
RE: Photoshop 6/7 problems with OptiCAL Monitor profiles
- Subject: RE: Photoshop 6/7 problems with OptiCAL Monitor profiles
- From: "Bruce J. Lindbloom" <email@hidden>
- Date: Fri, 14 Feb 2003 12:20:22 -0600
Bob Chase wrote:
>
Thank you so much. I have a feeling I'm about to finally understand the
>
complexities that give rise to this situation. By understanding, I (and
>
others if necessary) can adapt procedures accordingly.
>
>
I'll send you a separate email with files and data attached.
Bob sent me ICC profiles made with OptiCAL v2.5 and v3.7 (Windows), along
with the corresponding OptiCAL Information windows. From this, I can see
exactly what is wrong.
The OptiCAL Information window displays the actual instrument measurements,
including the white measurement (which was D65 in Bob's case).
The ICC profile that was made by OptiCAL had these exact same RGB
chromaticities in its colorant tags. This is *wrong* because the primaries
were not adapted from D65 to D50 per ICC specifications. This ICC profile is
plain old wrong.
When this (wrong) profile is loaded into Photoshop's "Color Settings" dialog
(as Bob had previously described), Photoshop did what it should, and adapted
the primaries from D50 back to the profile's white point (D65). But since
the "forward adaptation" had not occurred, this "backward adaptation" yields
chromaticities that bear no relationship to reality. This is not Photoshop's
fault -- it is a consequence of the broken ICC profile.
Profiles made with OptiCAL v2.5 and v3.7 both had this same problem.
If you use OptiCAL to calibrate your monitor to a D50 white, you will not
see the problem. The farther away from D50 you go, the worse the problem
becomes.
The copyright tag on the v2.5 profile is 1998. It is hard for me to believe
that this sort of problem could have been present for five years without
anyone knowing...
--
Bruce J. Lindbloom
email@hidden
http://www.brucelindbloom.com
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