Re: ColorSync and PostScript printing
Re: ColorSync and PostScript printing
- Subject: Re: ColorSync and PostScript printing
- From: Uli Zappe <email@hidden>
- Date: Fri, 4 Mar 2005 19:45:24 +0100
Am 04.03.2005 um 18:46 schrieb Chris Murphy:
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.)
It would be interesting to know if this behavior changes for a printer
that, unlike the CLJ 5500, defaults to an RGB color space.
The reasoning could be: tag untagged images with a color space other
than the printer's default color space (because they have to be
converted), but leave alone untagged images in the printer's default
color space (because they can be sent to the printer as is).
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.
So this definitely means that for the printer, the whole document is
either RGB or CMYK. Since cgpdftops will probably always convert to the
default color space of the printer (CMYK in case of the CLJ 5500), and
this default color space cannot be changed in ColorSync Utility, it's
really hard to see why the printer also registers RGB and Gray
profiles.
You said that PostScript files print directly. That would presumably
mean that you can print to RGB if you have an RGB PostScript file, but
on the other hand, in this case the (RGB) destination profile specified
in the PPD or ColorSync Utility wouldn't be used either, correct? If
not, this case could be an explanation for the necessity of RGB (and
Gray) profiles in the PPD.
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.
But the fact that changing the printer profile in ColorSync Utility
influences the result argues that the system does use the designated
destination profile, doesn't it?
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.
:-(
Have you tested this with the destination profile set to something
other than the factory preset in ColorSync Utility? I mean, if this
setting influences the result (as you say it does), then you can be
quite sure that the system uses this explicitly specified profile.
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),
What do you mean by "not a good one"? That should depend on what
destination profile you select, shouldn't it?
Bye
Uli
________________________________________________________
Uli Zappe, Solmsstraße 5, D-65189 Wiesbaden, Germany
http://www.ritual.org
Fon: +49-700-ULIZAPPE
Fax: +49-700-ZAPPEFAX
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