Re: ColorSync and PostScript printing
Re: ColorSync and PostScript printing
- Subject: Re: ColorSync and PostScript printing
- From: Uli Zappe <email@hidden>
- Date: Sat, 5 Mar 2005 01:53:50 +0100
Am 04.03.2005 um 23:34 schrieb Chris Murphy:
2.
When I compare a conversion using the same source and destination
profile manually (Photoshop or AppleScript or quartz filters), I get
consistent CMYK values between them. But I get very different CMYK
values in the PostScript file generated by the OS, when it supposedly
uses a (non-borked) manufacturer printer profile.
This is strange insofar as the result of using Quartz filters does not
differ from the OS approach for me (see below).
3.
Changing the PPD file so that the default color space is RGB, and then
creating a new printer based on that PPD still causes the the document
to be normalized to CMYK (the PostScript spool file is CMYK). So I'm
not sure what this setting does, if anything.
Very strange. If even this modification does not result in using RGB,
then there's really no point for providing an RGB profile.
OTOH, this explains perfectly well why custom profiles didn't work at
all with the old HP PPD: it registered only as an RGB PostScript
printer, which, as we know now, will still be sent CMYK data, while on
the other hand you could only specify an RGB custom profile in
ColorSync Utility which of course has no influence at all on the (CMYK)
output.
Things I can't answer with the information I have:
a.) Why does the system apparently use the manufacturer profile, but
the CMYK values are not anywhere in the ballpark as a conversion using
supposedly the same source and destination profiles?
Good question, which becomes even more confusing in view of the fact
that for the actual output, Quartz filters do not differ from the
system conversion (see below).
b.) The quality of HP's canned CMYK profile for Uli's printer. (i.e.,
if he still gets bad results using the quartz filter approach.)
I tried the Quartz filter approach you suggested with the following
results:
a) actual print: from what I can judge by the eye, there is no
difference to the print made directly with HP's canned CMYK profile (I
used the "HP Color LaserJet 5500" one that seems to produce the best
results). This result is confirmed by:
b) Soft-Proof in Preview: I measured the colors in the Soft-Proof view
of Preview and found that indeed they differ in no way from the results
I got when simply using "HP Color LaserJet 5500" as the printer
profile, without a Quartz filter. The only difference is that now, if I
uncheck the Soft-Proof checkbox in Preview, the image displayed doesn't
change at all: this is consistent with the fact that the Quartz filter
actually converted the image before.
So from my experience, Quartz filter <> System behaves completely
consistent immanently. So I would be inclined to think that HP's
factory profile is simply less than ideal, and only wonder why even
Apple's Generic CMYK Profile changes the colors more from RGB than I
think a CMYK conversion should.
Of course, this doesn't explain the differences to Adobe etc.
c.) Whether the printer would behave better if it were profiled RGB.
d.) How to get the OS to normalize a printer job to RGB for this
printer, instead of CMYK.
Of course, without d), c) is pointless. ;-)
If I get it right, with the "In-Printer" setting, Mac OS X will send
RGB data to the printer, so this is a way to judge the printer's RGB
capabilities. From casual experience, I used to think this provided
better results, but with the tests I've done now, I'm not so sure
anymore. Basically, the colors seem to be lighter in general; this is
good for blue which is far too dark otherwise, but bad for red which is
far too light now. (I got the impression "In Printer" would be better
by printing documents with lots of blue, but no red ...).
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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