Re: UCR in profile
Re: UCR in profile
- Subject: Re: UCR in profile
- From: Graeme Gill <email@hidden>
- Date: Fri, 07 Jun 2002 13:43:04 +1000
Jon Zax wrote:
>
Is there any way to determine the percentage of UCR being generated by a
>
CMYK profile?
First you would have to be able to define "% UCR" in a quantitative
way. The ICC specification certainly doesn't do so, even though
it allows for a tag to contain either a % UCR or a curve.
In practice a CMM is free to choose the amount of black it
uses for each output color in any manner it likes, not
necessarily following any rule that can be characterized
by a single number. For instance, a CMS that I am familiar with
generally uses a rule based on the possible locus of K values
for a given CIE output value, linearized by the L value.
The natural way of specifying this would be as a "% of linearized
locus", and this % can be a fixed number, a curve determined by
the L value, or anything you care to define, including the "% of
linearized locus of the input CMYK value".
Even if you therefore define "% UCR" as something like the
value 100 * K/(K + min(C,M,Y)), and compute it for each
output value in the profile CLUT, it may or may not
have a dominant value.
The answer therefore is "possibly, but in general, no".
Graeme Gill.
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