Re: Camera profiling with ICC et al
Re: Camera profiling with ICC et al
- Subject: Re: Camera profiling with ICC et al
- From: email@hidden
- Date: Mon, 15 Sep 2008 10:18:41 EDT
Hi Graeme,
I knew when I wrote this that it would probably catch your attention, but
this really is the subject of another thread. Mechanically you can, of course,
put whatever you want in an ICC profile, and many do to fix real workflow
issues. But earlier in the spec the reference is made about picture-referred. Your
interpretation is not at all unreasonable or uncommon because of the poor
structure/style and other ambiguities in the document. This is one of the things
we tried to fix with v4, but didn't quite, hence the new image state tag. But
lets not debate that here. You can corner me at CIC if you like...
Eic Walowit
Tahoe
<<
> A) All v2 ICC colorimetry is picture-referred and may assumed to be
> output-referred. This means that all v2 ICC rendering intents represent the
colorimetry
> of the desired reproduction, not the scene. Yep, even for the colorimetric
> rendering intent.
Hmm, I don't think so. ICC v2 profiles are perfectly capable of representing
scene referred values, since they contain pretty generic color transform
machinery, and colorimetric is certainly not meant to represent desired
reproduction, but instrument values. See the V2.4 spec A.3
"Rendering Intents" Page 68:
"The colorimetric rendering intents operate on measurement based
colorimetric
values as chromatically adapted to the reference viewing environment."
and the bottom of Page 80 in section D.3 "color measurement", and see
D9, D10 and D15 page 83-85.
> C) In v2, v4, and many other non-ICC profiling methods, there is no way
that
> I knew of to commmunicate weather the colorimetry is scene-referred or
> output-referred. This means you have to assume its output-referred, the
colorimetry
> of the reproduction, not the scene.
Since colorimetric intent should reflect instrument measurements, you can be
pretty sure then that it is scene-referred, and only relative or saturation
intents may have had a rendering transforms applied to them (although
there are problems in doing this well without knowledge of the output
medium).
Graeme Gill.
>>
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