Re: OS X ColorSync Utility
Re: OS X ColorSync Utility
- Subject: Re: OS X ColorSync Utility
- From: Dave Camp <email@hidden>
- Date: Tue, 09 Jul 2002 18:12:40 -0700
on 7/9/02 4:56 PM, bruce fraser at email@hidden wrote:
>
I don't disbelieve you, and I don't disbelieve your guy at Apple, but
>
what you and he say directly contradicts the evidence of both my
>
senses and my Spectroscan, so I suspect that neither you nor he knows
>
the whole story.
And I certainly don9t doubt you are seeing what you say you are. :-) I'd
really like to figure out what is going on here as well.
>
Printing from Photoshop 7 to two different (beta) Epson 2200s, and
>
printing the gretag 9.18RGB profiling target using the same driver
>
settings (salient points being Photoshop Print Space = Same as
>
Source, driver color management settings = No Color Adjustment), I
>
get basically identical prints from OS 9 and OS X. (Maximum delta-e
>
is 0.3, average delta-e is 0.09). I'm tolerably certain I had the
>
same results on the 1270, but I happen to be looking at the
>
comparison of the 2 2200 targets in MeasureTool right now.
My assumption to date has been that existing drivers are making some
assumptions about the source space of the RGB data. For example, some
drivers (especially less ICC savvy ones) are written to assume that the RGB
data coming in is always sRGB. Or the drivers are simply using an inverted
RGB lookup to generate CMYK values.
On OS 9, this would have been the case for images printed from apps that did
not provide a source profile with the print job. Since only relatively high
end apps (e.g. Photoshop) would provide a source profile, a driver would
have to fall back to assuming something to perform the color conversion from
less capable applications. I assume Epson is doing something more advanced
(they have always had good color, but ultimately, with no source profile,
some sort of assumption has to be made).
For OS X, I'm assuming most vendors are simply bringing their printer color
code forward with minimal changes (partly explaining why there are no CMYK
native inkjet drivers yet). This also means that any built in color
assumptions are brought forward by default, or the drivers are modified to
give consistent results to the existing OS 9 drivers so that customers are
not surprised by suddenly getting different looking output. That sort of
thing is very important to vendors, as surprises create tech support calls,
and tech support calls cost money...
Getting back to testing: my test scenario to validate that I could not print
a raw test target (as I was told would not work), was to create an untagged
CMYK TIFF file and print from Preview (this pre-dated Photoshop 7, maybe I
should try again). The driver was set to not give the OS any default
profiles.
As long as the default Document and Output profiles in the ColorSync prefs
panel matched, my driver was sent unaltered CMYK data (because there was no
transformation happening). However, changing the default Document or Output
profiles definitely altered the CMYK values I was passed.
So, having said that, I will step back and say there is at least one way to
get raw output: make the source and dest profiles match. Of course, you
would expect that to work. However, it does not seem to explain the case of
an RGB printer driver, unless your source document is tagged with the output
profile.
Have you tried printing the test target from any app other than Photoshop 7?
That might illuminate whether or not I'm completely high on crack, or maybe
Adobe is doing some behind the scenes trickery to give output consistent
with OS 9.
Dave
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