Re: Microsoft's color-management claims
Re: Microsoft's color-management claims
- Subject: Re: Microsoft's color-management claims
- From: Graeme Gill <email@hidden>
- Date: Fri, 23 Sep 2005 17:12:33 +1000
Robin Myers wrote:
As the inventor of the algorithms that formed the basis for ColorSync
1, I can assure you that the algorithms were matrix based and worked
extremely well on subtractive printers. In fact, for in gamut colors, I
was able to achieve very accurate colorimetric matches (within the
measurement error of my spectrometers and the printer tolerance). All
the calculations were performed with XYZ data. The algorithms also
handled seven colorant printers, and had a mechanism for gamut mapping
and primary adjustments such as adjusting the yellow colorant so there
would be no scum dots in the pure yellows (at the expense of some
colorimetric accuracy). The final ColorSync 1 release unfortunately did
not have these features and was restricted to a 4 colorant printer
model only.
I suspect this depends on the definition of "matrix". My use of "matrix"
was in the ICC, 3x3 sense. If you expand the definition to include
the type of colorant combination matrix used for Neugenbauer type models,
then I have no doubt that acceptable to very good printer models are
possible. That sort of thing doesn't plug into an ICC "Matrix" profile
though (although it could be fitted into an XYZ Lut profile I suspect),
and in my experience the approach works well on some types of printing
systems, and poorly on others, while LUT based models work more broadly.
If you are talking about 3x3 matrix models, then all I can say is that
I haven't stumbled across many printing systems that seem to work well
with such an approach. Even many CRT's that I've characterized have been
a poor fit to 3x3 matrices, in spite of them being additive devices !
When the ICC was formed it was decided not to unveil the algorithms I
invented but to work with the ICC to develop a LUT system. I do not
believe that the reason cited above was the determining factor for the
ICC using LUTs. More likely a LUT system was chosen because LUTs were
well understood by the members of the ICC and they already had
functioning LUT color matching solutions they could quickly convert to
use ICC based profiles. LUTs also allow for very non-linear behavior to
be encapsulated easily.
Well, of course I was not privy to the ICC's deliberations, so my
comments are naturally speculation based on my experience comparing
ICC Matrix profiles, Neugenbauer type models, and LUT based models.
That "LUTs also allow for very non-linear behaviour to be encapsulated
easily" was precisely the type of argument I was making.
Graeme Gill.
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