Re: Camera Profiling question
Re: Camera Profiling question
- Subject: Re: Camera Profiling question
- From: "dpascale" <email@hidden>
- Date: Sun, 14 Sep 2008 14:26:57 -0400
Rich,
Just to add on what Dana and Graeme have already said, and on which I
entirely agree, essentially the only way to re-purpose/correct a shot made
under one illumination to a shot done under another illumination is to
record a spectrum for each pixel as well as the spectrum of the scene light
(assuming it is uniform in terms of spectral content over the entire scene).
Such camera and processing suite do exist but are far from common.
The White-Balance tool and ICC profile technology do quite a good job,
considering that they work on derived tristimulus data (XYZ, Lab, RGB, etc.)
or CMYK, and not spectral data.
Danny
email@hidden
www.babelcolor.com
----- Original Message -----
From: "Richard Apollo" <email@hidden>
To: <email@hidden>; <email@hidden>
Sent: Saturday, September 13, 2008 9:10 AM
Subject: Re: Camera Profiling question
Rich Apollo
Prepress Mgr
Oklahoma Offset, Inc.
email@hidden
918-732-8168
"dpascale" <email@hidden> 09/12/08 8:52 AM >>>
The combination of the smooth or spikey illumination with the smooth or
irregular spectrum of colored objects will produce different colors. This
is
called Color Constancy, and this is the basis for the Color Inconstancy
Index which determines the color shift for a given color when changing the
illuminant.
In practice you can can always "normalize" your images so that they all
match for a given color. Since this is often done for white
(White-Balance),
you can obtain uniform white for all illuminations. However, nothing in
this
process says that a pinkish color will look the same agains a greenish
color
in all shots, since each color will/may shift differently with each light
source.
So there will always be a difference even if you do not want it (unless
you
manually correct the colors).
That's kinda' what I thought. Every time I see this argument erupt it
strikes me that there's a big disconnect in the community based on the
desires of the photographers involved.
The Star-Bellied Sneetches want the elements in the photograph to render
the same color under all lighting conditions, therefore camera profiling
doesn't work.
The Plain-Bellied Sneetches want the elements in the photograph to reflect
the lighting conditions, therefore camera profiling works.
To me it looks a lot like the difference between Absolute Colorimetric and
Relative Colorimetric - white point rendering or white point adaptation.
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