Re: CMYK/RGB printing confusion - please help!
Re: CMYK/RGB printing confusion - please help!
- Subject: Re: CMYK/RGB printing confusion - please help!
- From: Chris Murphy <email@hidden>
- Date: Wed, 2 Mar 2005 10:02:29 -0700
On Mar 2, 2005, at 8:38 AM, Uli Zappe wrote:
Hi everyone,
I had asked in
http://lists.apple.com/archives/colorsync-users/2005/Feb/msg00265.html
how you change the default color space (CMYK <> RGB) for a PostScript
laser printer (a HP Color LaserJet 5500 in my case) in ColorSync
Utility. Unfortunately, nobody seemed to have an answer.
I wouldn't expect an output device could be registered as being either
CMYK or RGB. It's one or the other. However I've seen some gimp-print
driven printers appear with both an RGB and CMYK print condition
(instead of media type) where in one I could select an RGB profile and
in the other I could select a CMYK profile.
The reason may well be that evidently this cannot be done. This is
what HP support tells me, and in fact, in the respective PPD there's
an entry to specify CMYK as the default color space, suggesting this
setting is indeed fixed.
But then, how do you manage to print something and use the RGB ICC
profile instead of the CMYK ICC profile of the printer? This must be
possible, or else it would make no sense for a PPD like the one of the
CLJ 5500 to provide an RGB ICC profile as well.
If they don't register the device as allowing RGB, then indeed it makes
no sense for the manufacturer to provide an RGB profile that you can't
use (except by doing an end run around ColorSync, and printing
pre-matched data from an application such as Photoshop).
HP support says that I have to switch the color space I want to print
with in the app I want to print from.
Absurd. HP support sounds clueless. If they a.) register the device
correctly, specify driver defaults that were used to build the profile
they made for the printer (RGB or CMYK), and provide a well built
profile that describes the printer's behavior with those settings - the
conversions necessary will all occur behind the scenes whether you use
Standard or In-Printer ColorSync settings in the print dialog (with
Standard generally being more reliable.)
To make things even more confusing, Preview's info panel provides no
information whether a PDF contains an ICC profile (it does with TIFFs
etc.), so I have no way to control in a print preview what kind of
color space the PDF is using.
Preview converts everything it opens to Monitor RGB (whatever profile
you have set for your primary display), and then displays it. That same
converted data is what gets printed. What should happen is ColorSync
will convert that data from Monitor RGB to the profile for your printer
if you choose to use the Standard ColorSync setting. This happens for
you behind the scenes. It's not something you should need to mess
around with.
Or do I get this wrong and the PDFs Mac OS X creates for printing do
not contain an ICC profile? - But then, how could it possibly tell
ColorSync to print with the RGB printer profile instead of the
(default) CMYK printer profile?
They do contain an ICC profile.
As you can see, I'm utterly confused, and I can't find any
documentation anywhere that's relevant for this problem. (Maybe this
is because several parties - Apple and the printer manufacturer and
maybe even an application software vendor - are involved.) So every
hint how to proceed with this problem would be greatly appreciated,
because I don't know what to look for, and am really lost :-/
HP support is probably not going to be able to tell you squat. You need
to find an engineer who worked on the PPD for Mac OS X, or the guy who
built the ICC profile.
The reason, BTW, I would like to have the option to use the RGB
profile for printing is that the CLJ 5500 prints far too dark colors
in CMYK mode. (I have no idea if this is a general CMYK problem, or a
problem specific to the CLJ 5500). If I switch off ColorSync
completely in the Print Panel (ColorSync > Color Conversion: In
Printer), the colors are much better (reportedly, in this mode the CLJ
5500 uses an RGB profile internally). But with this setting, I loose
the option of fine-tuning color by creating and applying a custom
profile; so I want to stick with ColorSync.
Chances are, the default settings in the driver are not putting the
printer into the same mode HP used to build the canned CMYK profile you
are using (that presumably they have provided to you). Until you find
the magic sequence of settings to get the printer back to that level of
behavior, the CMYK profile will continue to produce poor results.
Arguably it's still possible for it to produce poor results even with
the same settings. When was the original CMYK profile built? Was it
built for a pre-production unit? Have the lookup tables, black
generation, ink limiting functions in the printer changed since the
profile was built and the printer you actually bought?
You may invariably need a custom profile anyway. To print the target
correctly means NOT using Preview. You'll need to print using an
application that does not convert images when opening them, like
Preview does. If you're using any Adobe application, you can ensure
that you're getting a non-color managed target from which to have a
profile built. Then simply use that profile in the ColorSync Utility.
While this has fairly poor reliability with non-PostScript inkjet
printers using manufacturer's drivers, it does seem to work reliably
with the limited testing I've done with PostScript inkjet and laser
printers. (But the user interface is far far less than intuitive.)
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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