Re: MS Color Control Applet
Re: MS Color Control Applet
- Subject: Re: MS Color Control Applet
- From: Chris Murphy <email@hidden>
- Date: Tue, 4 Jul 2006 19:02:01 -0600
On Jul 1, 2006, at 12:53 AM, Graeme Gill wrote:
It's more complicated that that. All (useful) V2 profiles adapt the
monitor white point
to be D50 already. What's changed in V4 is that now even absolute
colorimetic intent
in display profiles have to adapt the display white point to D50,
because the ICC
have (wrongly IMHO) declared that an emissive devices white is to
be regarded
as the illuminant, rather than the devices media white point.
The idea is to prevent chromatic adaptation from occurring twice.
When the human has fully chromatically adapted to display white, and
the assumption on the part of the display profile is that the human
has not fully chromatically adapted, the profile building does some
chromatic adaptation when they should do none and leave any chromatic
adaptation to the CMS.
In an ICC v2 world, the end user's relative chromatic adaptation is
not defined and each vendor would assume something different. So they
fudged their profiles in a manner that meant you really weren't
getting actual measurement data in them anyway and it wasn't reversible.
In an ICC v4 world, they are chromatically adapted to D50 so that by
default there isn't going to be double chromatic adaptation. But the
CHAD tag being required if the media white is NOT D50 means that we
can reverse the adaptation to actually get measurement data and adapt
as needed - anywhere from none to full adaptation. The results are
actually better, both when converting from display profile to output
device as well as output device to display.
What this means in practice is a reduction in ICC functionality.
Using V4 profiles
and the ICC intents, it is no longer possible to do absolute
colorimetic
matching on monitors. You're stuck with relative colorimetric.
Umm, no. The assumption is that the human has chromatically adapted
to their display's white point, regardless of what it is. Further
chromatic adaptation for that white point is unnecessary when making
that assumption. BUT this doesn't mean that you don't get paper white
simulation to the display anymore with AbsCol (i.e. paper white
simulation in Adobe apps). All you have to do is try it. It still
works and in my view it's working a lot better than it used to.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
---------------------------------------------------------
Co-author "Real World Color Management, 2nd Ed"
Published by PeachPit Press (ISBN 0-321-26722-2)
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