Re: ColorSync and PostScript printing
Re: ColorSync and PostScript printing
- Subject: Re: ColorSync and PostScript printing
- From: Chris Murphy <email@hidden>
- Date: Mon, 7 Mar 2005 09:53:49 -0700
On Mar 7, 2005, at 8:57 AM, Rolf Gierling wrote:
Prelimary for further discussion:
As far as I can see until now postscript printing using
ColorSync->Standard
in the printing options behaves like this:
Conventions:
source is the profile of the tiff image I used
destination is the profile for the printer assigned in ColorSync
Utility>Devices>Printers
If you print to a registered CMYK device and:
source and destination are the same, the numbers are unchanged,
if source and destination don't match, matching ocurs, but the numbers
are not what you get in Photoshop or with AppleScript. (see below)*
I'm with you up to and including this point.
if source is untagged, Generic will be applied in both CMYK and RGB
(untagged to ISOcoated gives the same numbers as Generic to ISOcoated)
Untagged CMYK going to a CMYK destination is left alone regardless.
If the source is RGB, it gets matched to Generic CMYK first and is
then matched to the destination. (You can proove this by using
a manipulated Generic CMYK profile)*
That's very interesting, but I'm unable to reproduce the same values in
the PostScript spool file, to a test image converted with this
sequence. The numbers are still off by a significant amount. I'm
getting values for red of 74M, 46Y in one case, and 9C, 79M, 83Y, 3K in
the other. They are really two different numbers.
What printer and PPD are you using Rolf?
if the PPD says *DefaultColorSpace: RGB, matching of RGB-data is
source -> destination, but again the numbers aren't what I would
expect.*
I've changed a PPD to have a default color space of RGB, but it still
converts everything to CMYK even when I set up a whole new printer
using that PPD. I'm admittedly hacking a PPD and maybe there are other
things that have to be changed in order for the system to consider the
device described by the PPD as being RGB and needing to normalize to an
RGB space. Currently I haven't been able to get the system to do this
(for a PostScript destination of course).
You simply can't get reliable output if the source is in RGB.
It's increasingly looking like that is the case.
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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