Kodak CMM in Photoshop+scum dot Heidelberg+ProfileMaker
Kodak CMM in Photoshop+scum dot Heidelberg+ProfileMaker
- Subject: Kodak CMM in Photoshop+scum dot Heidelberg+ProfileMaker
- From: neil snape <email@hidden>
- Date: Sun, 22 Apr 2001 09:49:19 +0200
a question by pleader was asked to and responded on the Adobe user to user
forum post
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Topic ; by pleader Apr 15 2001
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PS6 ICC Profile Reassignment: 1% Contamination
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Thomas Knoll replied:
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I downloaded the "SWOP TR001 CHROMix ltGCR320.icc" profile run it though an
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internal Adobe profile testing program.
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It has scumdot problems in the Lab->CMYK direction.
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For example, in the Lab->CMYK direction, it convert pure PCS white to:
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CMYK 0.3417% 0.2607% 0.1264% 0.0000% for the perceptual intent.
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CMYK 0.3873% 0.2974% 0.3240% 0.0000% for the relative colorimetric intent.
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CMYK 0.3572% 0.2668% 0.1290% 0.0000% for the saturation intent.
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The problem is with ProfileMaker itself. It does not appear to be using the
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correct PCS white point encoding. Details of the PCS white point encoding can
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be found at www.color.org.
This certainly isn't new. A couple of years ago after converting images to
CMYK I had to manually move the end points in Photoshop to remove scum dot.
A very kludgey workflow and not possible in non image programs. The results
were always the best with the ACE CMM, thus I continue to use it for all
transforms. With the advent of Photoshop 6 most of my images going to press
are put into Eurocoated V2 transformed with again the ACE as this produces
clean reliable results considering the destination presses are assumed to be
run to manual density specs <unprofiled>. It should be noted that Black
Point Compensation MUST be on for this to work. Too bad that there isn't a
Eurocoated Web or LWC, that'd save the dance of cutting the 350% TAC black
back to 320% for Web. There are times that the images can be custom tailored
to Fogra idealised ISO 12647 whereas the profiles are made with
ProfileMaker. Here the scum dot problem is evident on rgb Adobe 98 going to
Cmyk on all of the above renderings with all the CMM's I have. As Chris
Murphy has many times noted the ACE minimizes scum dot better than the
others with these profiles by Gretag and also PrintoOpen by Heidelberg. Even
going Lab > Adobe 98 using the Heidelberg CMM puts 100L Oa 0b to 253 255
255.
I've become a little lazy in correcting out the scum dot especially
considering the presses are normally web or gravure so 1% is not going to
make it to the isolation of the plates (2% maybe).
My question is when the transformations place the pure white in the wrong
place in the Lab area is taking out the scum dot only superficially removing
the end points but leaving highlights and 1/4 tones influenced by this
misalignemnt?
Neil Snape
email@hidden