ICC v4, was: Gretag's IQueue 140 not processing correctly with V4 profiles
ICC v4, was: Gretag's IQueue 140 not processing correctly with V4 profiles
- Subject: ICC v4, was: Gretag's IQueue 140 not processing correctly with V4 profiles
- From: Chris Murphy <email@hidden>
- Date: Thu, 17 Nov 2005 11:00:06 -0700
On Nov 16, 2005, at 3:38 PM, Graeme Gill wrote:
And the fact that the reference PCS gamut hasn't been officially
released
yet.
Right! (A small point.)
Lets say you were using perceptual (because that's where v4 is meant
to make the biggest difference), then for v2->v2 where the v2
destination
profile is set to expect the gamut of the source v2, the results
should
be good.
The v2 destination doesn't really expect (explicitly) the gamut of
the source profile in any event. That's a big part of the problem
with ICC v2 is that the destination profile's gamut compression is
pre-baked at the time it's built, rather than being dynamically
computed based on the gamut of the source profile. The gamut mapping
for an sRGB image being converted for a photo inkjet printer (or
press) is the same for a ProPhoto RGB equivalent (i.e. take the sRGB
version, convert to ProPhoto RGB, then convert to printer).
With v2 it's a crap shoot as to whether you get something reasonable,
or substantially desaturated.
If you change this to v2->v4 where the destination v4 is set
to expect the reference PCS gamut (which is quite a bit bigger than
many
typical source gamuts), then you might well get a desaturated result.
Perhaps. I was under the impression the reference gamut was output
referred so while it would be bigger than sRGB, it would be no where
near as big as ProPhoto RGB. So maybe the reference gamut isn't
output referred, and it's going to be the job of the CMM and output
profile to do that. If that's the case, yes I'd expect desaturated
results.
If you are using a colorimetric intent, then it would be a surprise to
get any noticeable difference between v2 and v4 (modulo the
redefinition
of what absolute display colorimetric means of course.)
The white point handling is different so AbsCol conversions might be
better. I'm curious about comparing v2>v2 and v4>v4 proofing
conversions in this respect. That's something we can do today.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
-------------------------------------------------------------
Co-author "Real World Color Management, 2nd Edition"
Published by PeachPit Press (ISBN 0-321-26722-2)
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