Re: Epson Printers/Colorsync/OSX
Re: Epson Printers/Colorsync/OSX
- Subject: Re: Epson Printers/Colorsync/OSX
- From: Dave Camp <email@hidden>
- Date: Fri, 11 Oct 2002 11:22:54 -0700
Oh yes! My favorite topic. :-)
On Thursday, October 10, 2002, at 10:53 PM, Chris Murphy wrote:
>
However, Epson's not using ColorSync by default on either OS 9 or X
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(or ICM on Windows as far as I can tell). They use their proprietary
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color management, and use Photo-realistic mode. So ColorSync isn't
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doing a conversion as far as I can tell (with these settings, I get
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the same results in OS X and OS 9; which tells me ColorSync isn't
>
being asked to do anything at print time).
I don't think this is technically quite true (at least not according to
the latest ColorSync tech note and the printing group at Apple). While
you may not be observing any changes, that does not necessarily mean
ColorSync is not involved. As far as I know, and I've been told this
directly by the printing group, all raster data going to printers is
color managed by ColorSync and it cannot be avoided. OS X Print Modules
have no say in the ColorSync process, other than to provide a set of
default profiles to be used. There is no API to do this.
This of course has the downside of not being able to easily print
targets, which the printing group is aware of.
From the ColorSync tech note:
>
Printing Back-End
>
>
When printing on Mac OS X, ColorSync will match source data to
>
whatever profile the printer driver provides. For this reason, printer
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drivers should register profiles for their devices using the Device
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APIs as discussed earlier in this note.
>
>
Here are some profile changes which were made in Mac OS 10.2 by the
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printing system back-end for both raster and PostScript printing:
>
>
Raster Printing
>
>
If a printer driver provides no profile, ColorSync on Mac OS 10.2 will
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substitute the Generic RGB profile. ColorSync on earlier versions of
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Mac OS X would substitute the system profile.
>
>
Also, in earlier versions of Mac OS X, RGB ROMM was used as an
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intermediate color space by the raster back-end when the printer
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driver provided a profile for the printer. On Mac OS 10.2 the RGB ROMM
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space has been removed altogether, resulting in cleaner, more accurate
>
color.
This says that on OS X 10.1 and 10.2, in the absence of a default
profile from a print module, the source document was converted to
Generic RGB or the System Profile. There was not a case where a print
module would get unaltered raster data, unless the source and
destination profiles matched.
Again, I won't dispute what anyone is observing in their output.
However, I don't think the conclusion that no observable differences in
output necessary means that ColorSync is not in the print path is
correct. I think the imaging folks at Apple are just very very clever.
:-)
Dave
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