Re: How do one generate profiling patches (The hen or the egg)
Re: How do one generate profiling patches (The hen or the egg)
- Subject: Re: How do one generate profiling patches (The hen or the egg)
- From: email@hidden
- Date: Wed, 23 Apr 2003 11:35:02 EDT
In a message dated 4/23/03 6:42:43 AM, email@hidden writes:
>
> You seem to be viewing this backwards; your print 100% Cyan, and read the
>
> result as a Lab value. That tells you want value will result from that
>
> recipe,
>
Yes essentially you get a lab (or spectral reading)
>
>
> and also what values of Cyan will be out of gamut on that device.
>
>
How? The lab reading from the printed paper will only tell you the
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lightness
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and a+b coordinates of the printed Cyan.
>
Exactly, which defines that color in a universal (almost) space.
>
You still need the reference value
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to see how far off your reading is,
>
You are mistaking this for scanner profiling, I think. The relationship here
is CMYK recipe to Lab value. You already know the CMYK values involved in
printing that patch. There is no "how far off" involved here.
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and thus define the outer limit of the
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gamut (how cyan can cyan be).
>
Any color with similar hue and brightness, and higher saturation than the
measured Lab value will be out of gamut. There is no meaning to a Cyan beyond
100% C on a given device.
>
Only when you know what is the maximum
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printable cyan is can you define a gamut.
>
We just covered that; there may in fact be no increase in saturation beyond
90% C, which should ideally be covered by linearization/ ink limiting instead
of profiling, but that works in the other direction.
C. David Tobie
Design Cooperative
email@hidden
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