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 12:28:29 -0700
On Mar 2, 2005, at 11:37 AM, Uli Zappe wrote:
\/ Printers
\/ ColorLaserJet 5500 *
CMYK Matching Profile *
Gray Matching Profile
sRGB Matching Profile
Do they let you associate a custom profile for the "sRGB Matching
Profile"? This isn't making much sense. Is the manufacturer specified
profile in this location sRGB? That would make sense. And then you
could replace it with something better if you made a custom profile.
But calling the setting "sRGB Matching Profile" doesn't make sense to
me unless a.) the manufacturer specified profile is sRGB, and b.) you
can't change it to anything else.
The EPSON Stylus Photo R200 that I show as a comparison has several
entries for different profiles, too. However, these are all RGB, and I
suppose they get chosen automatically dependant on what kind of paper
I specify in the Print panel.
Theoretically. The Epson drivers are luny when it comes to supporting
ColorSync correctly.
But OTOH the PPD specifies factory profiles for all color spaces:
*% =================================
*% Product/PPD Version Information
*% =================================
*% PPD File Version Information
*cupsICCProfile RGB../sRGB Matching Profile:
"/Library/Printers/hp/Profiles/sRGB_A.icc"
*cupsICCProfile CMYK../CMYK Matching Profile:
"/Library/Printers/hp/Profiles/CMYK_A.icc"
*cupsICCProfile Gray../Gray Matching Profile:
"/Library/Printers/hp/Profiles/Gray_A.icc"
Now, of course the question is, why would the PPD specify RGB and Gray
profiles if these cannot be used in any way?
You would think ColorSync would normalize everything to Gray and CMYK
for a CMYK device. Any RGB content would be converted to CMYK as well.
I'm a little mystified as to what exactly the OS is going to do if an
application submits RGB data for a printer that has a default color
mode of CMYK.
Maybe the idea is if you edit the PPD to change the default color space
to RGB? Then the OS would normalize everything to sRGB and the printer
would have to do an internal conversion to print sRGB color correctly?
Documentation is underrated.
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
What exactly means "register" in this context? That CMYK is specified
as default? I mean, the PPD seems to "register" CMYK, RGB and Gray
with the ColorSync Utility ...
Registered print conditions. For your laser printer, it's based on
color model. For your Epson printer it's based on media type.
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.
<Sigh> This goes on for over a year now ...
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.)
Compared to what I see on the screen in my original document, for me,
"In Printer" is, well, acceptable, while "Standard" is far too dark.
It is consistent with the Soft-Proof in Preview, though, that is also
far too dark! (E.g. a blue of HSV 216-73-79 becomes 214-69-65 in the
Soft-Proof mode of Preview, and the print looks accordingly.)
Sounds like a jacked up profile. The B2A portion is converting too
heavily (incorrectly) and the A2B portion is predicting it! It would be
interesting to take a granger rainbow and round trip it through this
profile. Lab to CMYK and then CMYK back into LAB and then compare the
LAB values. they won't be identical, but they should be in the ballpark
for in-gamut colors.
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.
Always? I mean, even when I have an image with an embedded CMYK
profile? This gets converted to Monitor RGB and then back to CMYK in
case of a CMYK printer?
Yes. Preview is not a good color management citizen.
On a side note, wouldn't that mean that you should always use Monitor
RGB as your working space? I mean, it's one conversion less, and
that's good, isn't it?
"working space" is an Adobe term for settings found in Adobe
applications. You can't set a working space for non-Adobe applications.
Or do I get this wrong and the PDFs Mac OS X creates for printing do
not contain an ICC profile? [...]
They do contain an ICC profile.
My confusion is that Preview does show an ICC profile and a color
space for images (TIFF etc.) I open in it directly, but *not* for
PDFs. Is this simply a bug in Preview's info panel?
Two points of view:
1. It's a limitation of the info panel because it appears designed to
show only one profile. PDF is a container format where each object can
have its own profile, so an interface showing only one profile would be
misleading. So the interface, when it comes to PDF, allows us to either
be mislead (show only one of possibly dozens of embedded profiles in
the PDF), or to be confusing (show nothing).
2. Upon opening the PDF, the pages are converted to Monitor RGB, so the
source profile is technically Monitor RGB, even though it's not
embedded in the PDF.
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.
Over that long last year, I think I have come as close to the HP
engineers as I will ever be able to come ... :-(
How far away are you from Barcelona? I think they have an entire cabal
of engineers there. You could just pay them a visit. Ha!
You may invariably need a custom profile anyway.
Well, that's what I intend to do. It's just that before I start
dealing with/investing in that, I wanted at least to make sure that I
am ready for that in that I have understood the necessary
prerequisites. So far I haven't. Up to now, I didn't even know if I
need to build a custom CMYK profile, a custom RGB profile, or both ...
:-/
I think just a CMYK profile. From that you can have someone use the
trick in Photoshop to output a grayscale profile based on the K channel
in your CMYK profile. Any gray content will still require the gray
profile, not the CMYK profile. The RGB profile seems superfluous if the
default model of the printer is CMYK. The question is whether the OS
is really going to normalize everything, RGB, CMYK and Gray to just
CMYK and Gray.
Email me the PPD for the printer. I'll set up a dummy printer, print
PostScript to a file and see what I get from a few apps.
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.
If possible, I'd want to avoid buying an Adobe app for just *that*.
=8-} Any other way? What about printing directly from the command
line (lpr)?
Never tried it. Surprisingly enough Mail.app might be able to do this :)
If you take the CMYK target, and use the Embed Specific Profile
AppleScript to embed your canned CMYK profile into the image, then open
it in Mail.app and print it from Mail.app - the source profile is
manufacturer profile, and the destination profile is the same profile
(still set in the Colorsync Utility) so ColorSync should null
transform. Build a profile from the target, and replace the profile in
ColorSync Utility. It might work, you'd have to test it.
And BTW, this illustrates the rather poor state of affairs of color
management on OS X. We are so needy for Adobe applications, and there's
a lack of an explicit OFF switch for color management that we can't
even easily print profile targets to make custom profiles for our
devices without having a square dance under a full moon with a dog, a
pig, and a pony. The situation is pretty ridiculous...
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.
What I find additionally confusing, though, is that even converting an
RGB image into the Generic CMYK Profile (in the ColorSync Utility)
makes the image noticeably darker. Shouldn't at least this generic
conversion from RGB to CMYK leave the image as identical as possible?
I thought that's what color management is all about?
Yes.
Tell you what you should do. Try changing the CMYK profile in the
ColorSync Utility for your printer to some other CMYK profiles and see
what happens when you print. Is there a difference?
(But the user interface is far far less than intuitive.)
Apple writes in the introduction of "Color Management with Mac OS X
Panther":
"With Panther, it is faster, easier [...] than ever to achieve
consistent color."
Faster and easier than what? Jaguar perhaps? That was Mac OS X public
beta #2.
That book, commissioned by Apple, laments the bypassing of ColorSync by
Adobe applications and yet that's the only way to get the best possible
results due to lack of black point compensation and rendering intent
selection in Apple's implementation. Plus, the lack of an
aforementioned Off switch so we can easily print targets without an
Adobe application.
A big part of the problem is the lack of effective communication and
documentation between developers and Apple. I'd bet that the reason so
many developers aren't doing the right thing with color management in
their applications is because of the lack of adequate documentation
explaining how to do it correctly. So far the situation from the end
user perspective hasn't improved much with successive releases of the
OS.
And I thought I was an experienced computer user ... :-/
That's not enough. You need a dog, pig, pony and a full moon. Oh and
you need to learn how to square dance. (Didn't you know color
management has an obscure cowboy origin to it?)
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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