Spot Color tables in Best ColorProof
Spot Color tables in Best ColorProof
- Subject: Spot Color tables in Best ColorProof
- From: Marco Ugolini <email@hidden>
- Date: Sun, 01 Jun 2003 13:13:37 -0700
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Roberto Michelena wrote:
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The problem lies in the gamut mapping built into the profiles.
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Provided your proofer (meaning BestColor+printer+media) is well profiled,
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the Lab value you ask for should be the Lab value you get, within a
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tolerance (for example 2 dE), *if* it is within the gamut. That means, for
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the in-gamut Pantones, filling their Lab values into Best's table should be
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enough.
That may be true some of the time, but each printing device lives within its
own color space, and the same coordinates that describe an LAB color in the
abstract do not necessarily produce the closest result to the ideal on the
device at hand without further intervention. One may still have to move the
values around somewhat to find a closer match, specially if the Delta E
starts to exceed 3.
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Probably the best solution would be for Best to implement an algorithm
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similar to Praxisoft's ColorCompass Xtension for Quark, in which for spot
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color it iterates Lab values in and out of the profile until it finds the
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minimum possible dE. It is easy and fast given that you're looking for a
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single point.
That is exactly what I would have in mind. Isn't there a product out there
for general use, or a function in one of the existing professional packages
(ProfileMaker, etc.) that offers a routine for zeroing in onto that single
point in the device's color space where the Delta E is minimized?
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Meanwhile you could try a Photoshop trick in which you paint Lab gradients
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around the value you want, then transform to the device profile and back to
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Lab, and subtract that resulting image from a flat tint of the Lab value
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you wanted to achieve.
Correct me if I'm wrong, but that device profile in your test would need to
be something other than the one created via a CMYK test chart for CMYK
output (say, the TC3.5 CMYK): it would need to be one that charts the
LARGEST printable color range on the device, which, I guess, would be done
via an RGB test chart (like TC9.18 RGB). Is that correct?
Point is, if you are trying to proof an image containing both CMYK
continuous tones AND areas of PANTONE colors (a typical scenario in
production work for packaging), how do you output it to proof so that you
RIP the correctly color-managed values for the CMYK elements of the image
and at the same time the color values for PANTONE colors that may be OUTSIDE
that CMYK space, all in the same one printout?
In other words, if the device's CMYK profile only describes A PORTION of all
possible colors achievable on a specific inkjet printer, how do you map line
colors that are outside that CMYK range but still INSIDE the device's
printable range?
Thank you for bearing with me, Roberto.
--------------
Marco Ugolini
P.O. Box 1838
Mill Valley, CA 94942
home (415) 383-4527
cell (415) 902-8344
email@hidden
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