[argyllcms] Re: Camera Profiling using ArgyllCMS
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 29 Nov 2008 12:31:43 +1100
Nikolay Pokhilchenko wrote:
It's exactly what I dream about! You are "hit the mark"! I think the RAW
channel data
can be linearised equivalently at a stage before conversion to XYZ because of
camera
design. I suppose there will be enough simple matrix conversion to XYZ after
linearisation without any LUT. That profile will be most exact because of it
may be
physically natural and correct.
That's one approach, although profiling using a test chart, particularly
one composed of real world spectral samples, leaves other non-linear
possibilities though. The basic issue is that if a sensor has spectral
sensitivities that are not a linear transform of those of a human observer,
then it simply doesn't see the world in quite the same way, and a single
matrix transform may not be the optimal way of making it approximate
a human observer. If something is known or assumed about the statistical
distribution
of different colorant reflective spectra being photographed, then it
may be better to (effectively) use different transform matrices for
different colors. A CLUT based profile has an equivalent effect.
Graeme Gill.
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