Re: ColorSync and PostScript printing
Re: ColorSync and PostScript printing
- Subject: Re: ColorSync and PostScript printing
- From: Chris Murphy <email@hidden>
- Date: Sun, 6 Mar 2005 11:45:09 -0700
On Mar 5, 2005, at 5:54 PM, Rolf Gierling wrote:
1) There is no difference between untagged and Generic CMYK tagged
files.
If the printer is set up to use an output profile, same color matching
ocurs.
(this is in opposite to what I understood Chris said)
The PPD for the printer must register printing conditions with
ColorSync. You will find these in the ColorSync
Utility>Devices>Printers (or Proofers). Chances are there isn't a
registered profile for the printer, which means it's using Generic
CMYK. Since you also used Generic CMYK for your tagged file, there was
a null transform. This is why I never use Generic CMYK (or Generic RGB)
when testing.
2) If the file is tagged with anything else, matching ocurs, but I
don't get the
numbers that I get for example in Photoshop. (This is what Chris sees)
Good to know I'm not the only one!
3) If the printer is set up with no profile in the ColorSync utility
(unknown or
lost profile, I don't know the english phrase), things get silly:
If I print directly to the RIP, the file is obviously RGB!
Hmm, interesting.
If I save the file as postscript first (and I would have suggested
that this is the spool file)
and then drag that file onto the printer symbol, its CMYK again, but
again the numbers
are not reproducible in other apps.
Save File as PostScript from the print driver is not the same thing as
the PostScript file that would have been sent to the printer. You need
to extract it from /var/spool/cups/tmp - and the only way to do that is
to print without the printer connected. Otherwise the PostScript file
is sent to the printer, then deleted shortly thereafter.
Another observation is, why can you select non CMYK-profiles for an
CMYK-device
in the colorsync utility.
Yes. It seems like a bad idea to me too.
This and the behaviour of RGB-files has still to be done.
In my tests, all RGB is converted to CMYK. The problem is that the CMYK
values are wrong, given what the source and destination profiles are
supposed to be.
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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