Re: Photoshop CS4 DeviceLink CMM Engine
Re: Photoshop CS4 DeviceLink CMM Engine
- Subject: Re: Photoshop CS4 DeviceLink CMM Engine
- From: Marc Levine <email@hidden>
- Date: Mon, 27 Apr 2009 21:56:48 -0400
On Apr 27, 2009, at 9:26 PM, Joseph Yates wrote:
The reason I ask is that - at least on my hardware calibrated Eizo
monitor -
when selecting a different CMM in Photoshop's Convert to Profile
Advanced
(Conversion Options) I see distinct changes in the preview - mostly
highlight areas.
I would expect this when using standard profile-to-profile transforms,
but not with a link.
No difference when choosing either Adobe (ACS) or Adobe CMM
But a definite difference between the Adobe's and Apple CMM or
BasICColors
CMM
Hence my original query about the option to choose a different CMM
during a
Photoshop devicelink conversion.
In the above example, are you using profile-to-profile (input/output)
or a link profile?
If you are correct also about the benefit of not having to choose the
parameters of the transform - such as rendering intent - then even
though
Adobe does include these "options" - changing these - say from
Absolute to
Relative - will have no effect on the actual transform correct?
That's the way it SHOULD work. Considering the link is prebuilt with
those parameters already defined, they should basically be dead
switches when selecting a link in Photoshop. I am not sure why they
remain active when selecting a link in PS. Maybe some kind of "extra
magic" or maybe a bug. (Gasp!)
; )
Marc
Regards,
Joseph Yates | Pacifica Island Art | Maui, Hawaii
I think the right answer to this question is:
Should it matter? An ICC link transform is a "bundled transform". In
other words, the transform contains all of the color pieces (input
space, output space, rendering) required to make a digital color
transformation from one color space to another. The engine that
applies the link should be insignificant because all of the numbers
were crunched when the link was made, not when the link is applied
(as
opposed to standard input/output transforms, where the CMM needs to
do
some heavy lifting "on the fly").
I suspect that, if there was a big difference in CMMs (which...I'm
not
sure there is these days), then you might see it in the link-building
process. This is trick-answer as well because I'm not sure which (if
any) link profile-building softwares give you a choice in which CMM
you can use to build a link. Chances are, the CMM that a software
uses
is pre-selected by the software manufacturer and then hard-coded.
Last comment is: hopefully, none of this matters because.... one of
the 2 main benefits of a link is that YOU DON'T NEED TO THINK about
all the parameters of a transform (including "Which CMM?" and "Which
rendering intent?"). It's all baked in. This ensures that you get
consistent color transformation by whatever means the link is
applied.
The other benefit, or couRse, are the extra goodies you get by
knowing
the input and output space when you build the transform (e.g. special
handling of pure colors, secondary colors, entire channels, ink
savings, black-point compensation, etc...)
Hope this helps,
Marc
--
Marc Levine
email@hidden
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