Re: Microsoft's color-management claims
Re: Microsoft's color-management claims
- Subject: Re: Microsoft's color-management claims
- From: Tim Vitale <email@hidden>
- Date: Thu, 22 Sep 2005 18:04:06 -0700
If the XYZ PCS uses matrix-based profiles, and WCS will be using XYZ
PCS, then profiles in WCS will be matrix-based rather than the
predominately LUT-based device profiles in the ICC system. Of course,
this generalization excludes the matrix-based ICC working space profiles.
The earliest version of ColorSync was based on color equations, XYZ
matrix equations, <http://en.wikipedia.org/wiki/ColorSync> rather than
LUTs. However, as the story goes, it was converted to a LUT-based
system to allow peripheral manufacturers to differentiate their product
lines.
Assuming the above, it would seem that WCS is closer to the original
intent of ColorSync. It might restore the purity of the original
equation-based color correction system from the current LUT-based
profiles with their "secret sauce" and Lab PCS. OK... I do have problem
with the Lab PCS, so I'm not troubled by trying something new. ...but
when did MS make an improvement in anything...
The problem I have with the Lab PCS is that it makes the following
irreversible changes in the actual color numbers, not the perception of
the color:
(1) desaturates yellows
(2) desaturates greens
(3) some blues go purple
(4) some reds go orange
due to the non-uniformity of the Lab space shown in
<http://www.brucelindbloom.com/index.html?MunsellCalculator.html> and
<http://www.brucelindbloom.com/index.html?MunsellCalculator.html>. Most
folk don't notice these issues, but for me, I spend considerable time
correcting their effects in the proofs, after those great Atkinson
profiles makes the grays neutral on the Epson 9600.
I know there are *profound* problems with "perceiving" color in the XYZ
color space. And, I know that adjusting neutral lightness in XYZ is not
a uniform function, but I assume that the WCS profile editing software
will have to translate back and forth through XYZ matrix equations. If
that is so, I wonder what the color space for perceiving color will be?
Back to RGB again? That would be an improvement for me, anyway. I have
so many problem jumping between RGB and Lab with most clients.
Just for completeness of information, see
<http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html>
for 3x3 matrix equations used for converting between RGB and XYZ. And,
Wikipedia for a explanation of XYZ and its sources
<http://en.wikipedia.org/wiki/CIE_1931_color_space>.
Tim Vitale
Preservation Associates
1500 Park Ave
Suite 132
Emeryville, CA 94608
510-594-8277
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