ColorSync and PostScript printing, was: CMYK/RGB printing confusion - please help!
ColorSync and PostScript printing, was: CMYK/RGB printing confusion - please help!
- Subject: ColorSync and PostScript printing, was: CMYK/RGB printing confusion - please help!
- From: Chris Murphy <email@hidden>
- Date: Fri, 4 Mar 2005 10:46:18 -0700
OK after playing with Uli's PPD and figuring out how to get the final
PostScript file that would have been sent to the printer, here's what
I've found:
1. Well behaved Cocoa applications like Mail will produce a PDF spool
file containing mixed mode objects as they were in the application
itself. All embedded profiles are retained in both RGB and CMYK.
Untagged RGB is tagged with Generic RGB. Untagged CMYK is left untagged
CMYK. (So you could print a CMYK target to a PostScript printer from
Mail.app, and reliably get an unmodified target from which to build a
profile. Not so for an RGB target.)
2. cgpdftops converts the objects in the PDF to a single CMYK space
based on their source profiles embedded in the PDF, and an unknown
destination. That is, I'm not absolutely sure what profile the system
has selected as the destination. Did it correctly select the
destination profile specified in the PPD file by the manufacturer? I'm
not sure.
3. If I change the profile specified by the manufacturer in the
ColorSync Utility, the CMYK values in the PostScript file are
different. So this setting for this printer does affect the end result.
4. When I use what I think the destination profile SHOULD be with
Photoshop or AppleScript, I get different CMYK values (sometimes
substantially different), than the system produced PostScript that
would go to the printer.
Unfortunately this means I can't confirm where the problem is. I can't
confirm for certain the OS is using the destination profile I want it
to use, and I don't know if that might be a PPD problem or a system
problem. Based on the PPD, which is rather straight forward, and the
fact that changing the destination profile for this printer in CSU
causes a change (but not a good one), something is awry somewhere in
the system. But without more PPD's and printers and testing, and a way
to confirm what the destination profile the system is actually using -
I can't be sure. But at this point, I can't say I'm confident in
ColorSync color managing any output to a PostScript printer correctly.
(This is using ColorSync>Standard, not ColorSync>In-Printer.)
If *anyone* has gotten this to work with their printer, I'd REALLY like
to hear about it.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
-------------------------------------------------------------
Co-author "Real World Color Management, 2nd Edition"
Published by PeachPit Press (ISBN 0-321-26722-2)
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