Re: Microsoft's color-management claims
Re: Microsoft's color-management claims
- Subject: Re: Microsoft's color-management claims
- From: Robin Myers <email@hidden>
- Date: Thu, 22 Sep 2005 23:11:23 -0700
On Sep 22, 2005, at 8:57 PM, Graeme Gill wrote:
<snip>
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.
Not a very likely story. Matrix based profiles only work on devices
that have additive behaviour (essentially the colorants don't
interfere
with each other). Practically no subtractive devices (such as
printers)
behave this way, so matrix profiles work really badly for them. LUT
based profiles on the other hand, are very general, and will work OK
to very well on almost any sort of device.
Dear Mr. Gill,
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.
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.
Robin Myers
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