I'm familiar with the principles of GCR and UCR. (I usually do the process manually.)
for one particular image, I've opted to let PS do the work, and I've used Convert to Profile and used SWOP, 15% GCR Heavy. I have a lot of gray(-ish) clouds and sky, and this swapped out the predominantly 3-color with mostly black, while leaving (most of) the visual integrity.
But now I'm placing it in an InDesign file, and outputting to a North American Prepress, SWOP (Coated) CMYK profile, and it's putting the colors back where they were!
I can't output the whole layout with the GCR profile, as that would affect the other art, which I can't do.
I've tried embedding the profile, not embedding the profile, changing the color settings when placing the art, and either the color goes completely off in another direction, or if it visually stays the same, it's back to the 3/c "gray" that I don't want swinging wildly in hue on press.
(Next Question: how do you combine part of an image that's been converted to a GCR profile into a normal SWOP CMYK image?)
'Outputting to a new CMYK profile' goes through Lab - the original
Black generation will be destroyed.
In a clean CMYK workflow I would prepare all single images by
appropriate GCR profiles and export from InDesign to PDF by these
1. No color conversion
2. No Output Intent
3. Include all Profiles
A unique Output Intent (2) ist not possible - would be wrong.
Include all Profiles (3) is quite useless for printing, but it would
allow to view each single image more or less correctly.
For the 'Next Question': In the moment I don't have a better
suggestion but Convert to SWOP and apply Channel Mixer
to a selection.
Questions like these are extensively discussed in Dan Margulis'
book about Photoshop:
(In any case of doubt - I'm referring to an older edition).
Best regards --Gernot Hoffmann
thanks for the prompt reply
I'm pretty sure Output Intent is a requirement for PDF/X-4, which we're using as a standard. This way we get accurate (?) color in a computer to plate workflow.
I'm guessing that if I included individual profiles in the PDF, the plate setter at my press vendor would just do the same thing. I guess I need a Device Neutral CMYK, which I seem to recall PS can't do.
Right now I'm trying to do it manually using Curves, but it's clouds with gray, blue and purple areas, and I'm having to do those color ranges each with their own curves, which is painstaking. the GCR did it great in one shot (with some experimenting).
Yes, Output Intent is a requirement for PDF/X-# standards (don't know
exactly for which), but that's definitely not required for printing - it's good
just for a correct preview.
I can see a couple of difficulties: on the one hand, you want to use a
standard process, as defined by a standard ICC profile - on the other
hand you're disregarding the RGB-CMYK conversions, as provided
by such a profile.
The solution, in my humble opinion, is one profile which is better adapted
to your images.
For printing RGB-gray images by 8 inks on an inkjet I have such a profile.
The profile generation is based on one printed target, then using the
strongest available GCR, starting at 0%, which is possible in GMB Profile-
(The purpose is to stabilize the gray against bronzing and metamerism).
Best regards --Gernot Hoffmann
that's what I'm coming to realize — I need to color correct in one profile and leave it there
I'm having a bit of luck with Channel Mixer, but I'm finding it lacks the finesse of Curves. I also have to different ones for different ranges, as it's not uniform. I just liked the Convert to GCR profile, as it did everything quite handily.
As far as I know, the Output Intent (or any embedded profile) just tells the printer, "this is what I want it to look like," before the RIP on the plate setter applies its own curves. It may be a moot point. We use different press vendors (in different countries) with different presses even amongst themselves. I'm saying, "it looks like this in SWOP Web Offset," and they have to match on their output device.
To be clear, neutral colors made up of predominantly CMY tend to vary widely through a press run, especially in the mid to lighter tones, where a 4-6% shift in ink is really noticeable. My aim is to fill the range with mostly black to minimize the shift.
All you have to do is set your InDesign output settings to not convert to the output profile. I'm trying to remember the language in the dialog box - something like "Don't Convert Colors" or close to it in the output tab in the export module. That way, you can combine whatever profiles you want from as many images and they'll all remain intact. I do this all the time and it works perfectly. Another fine example of completely screwed up default preferences from Adobe.
On the actual profile with heave GCR, I would use Gretag's free ColorLab app to basically reverse engineer the profile data from SWOP v2 if that's what you're using and then import the subsequent Lab data into ProfileMaker and build the new profile there. MUCH much better than using the old classic CMYK engine and beats the hell hands down out of using the crappy Channel Mixer method, which was shown to me by a supposedly high end shop in Orange County, but only hosed any semblence of shadow detail.
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