Re: Profoto
Re: Profoto
- Subject: Re: Profoto
- From: Steve Upton <email@hidden>
- Date: Fri, 30 Nov 2001 22:10:38 -0800
At 5:16 PM -0800 11/30/01, email@hidden wrote:
Bruce wrote: "The ICC profiles supplied with Photoshop, Illustrator
and InDesign are full-blown ICC profiles that support all rendering
> intents, and have true media white and black points."
>
Robin Myers said in my interview with him that "the ICC only
includes a relative colorimetric table and uses a mathematical
transformation to create an absolute colorimetric result" and that this
isn't always the best; are you saying that these Knoll profiles actually
include an absolute table as well as a relative and don't have this issue?
No, the "Knoll profiles" are regular ICC profiles that have relative
colorimetric tables. The CMM can use the white point of the profile
to create abs col transforms if desired.
The main issue that can occur with this is the chromatic adaptation
algorithm used. When a profile is originally built, the measurements
are - by definition - absolute. That is, the white point is the paper
white point. When the tables are calculated the paper-dependence is
removed from the numbers through chromatic adaptation calculations.
When the profile is used by the CMM, it needs to choose an adaptation
algorithm that matches the one used in the original calculation of
the profile if you are to get the best results. The current ICC spec
does not have a mechanism to note the method used though, so the CMM
is left guessing. The newer, not yet released version of the spec is
to include a tag which allows this to be recorded. Then the profile
can be used in a more appropriate fashion.
Regards,
Steve
________________________________________________________________________
o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX
o email@hidden 206.985.6837
________________________________________________________________________
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