Re: Comparing output profiles
Re: Comparing output profiles
- Subject: Re: Comparing output profiles
- From: bruce fraser <email@hidden>
- Date: Sat, 19 Jul 2003 16:37:33 -0700
At 7:10 PM -0400 7/19/03, Derek Cooper wrote:
Bruce,
In RWCM we have instructions for doing the same kind of comparisons
for output profiles, but I suspect that that's not what you're
looking for.
Page reference? I flipped through it but couldn't find any reference
to that process. I think there's a leap made assuming that the
reference file is already in LAB space.
pp247-250.
No, the reference file is always in the color mode for which you're
building the profile -- RGB or CMYK.
You have one set of LAB values from the measurements. These tell you
what actual color the device produces when fed the numbers in the
target (or target reference file).
You can produce a second set of LAB values by assigning the profile
to the target and converting it to LAB. This gives you the LAB values
the profile predicts. Comparing those to the measurements shows you
the accuracy of the device-to-PCS tables.
You can then take these LAB values, print them through the profile,
and measure the results to produce a third set of Lab values.
Comparing those with the predicted LAB values shows you what's going
on in the PCS-to-device tables.
Finally, you can compare the original measurements with the Lab
values that result from the predicted LABs printed through the
profile.
The best tool I know for doing what you want is Steve Upton's
ColorThink. It lets you compare both the gamut of source and
destination profiles, and, more usefully, the gamut used by a
source image with the destination profile, as 3D graphs. (It does
much more, and I find it indispensible.)
Ah, more toys! I'll check it out and see where it takes me. I've
been running in to some "issues" profiling a 2000P for a client. I
know those printers have issues, but they do have the ability to
perform quite nicely.
The biggest issue I find with the 2000P is that the yellow ink has a
green response that isn't triggered at all by tungsten, but gets
progressively stronger at illuminants above 5000K. It's more
sensitive to variations in the illumination than any other print
process I've encountered.
--
email@hidden
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