Re: Photoshop CS4 and DeviceLink profile
Re: Photoshop CS4 and DeviceLink profile
- Subject: Re: Photoshop CS4 and DeviceLink profile
- From: Koch Karl <email@hidden>
- Date: Tue, 02 Dec 2008 08:45:02 +0100
Hi Louis,
I wrote an article for a Danish magazine on this subject, here it is
(minus the images). A bit lengthy for a forum like this, but I don´t
have time to edit it.
Good News – Bad News
The good news is, Adobe Photoshop is now – 15 years after the
"invention" of ICC color management and 9 years after Photoshop 5, the
first ICC aware version of this de facto standard in image retouching
– able to use 3 additional types of ICC profiles which were defined
back then in the early 1990s. For the bad news, read the article.
Besides the previous ICC profile types, Photoshop 11 or CS4 now offers
the option of using Multi-channel (nColor), DeviceLink and Abstract
profiles when converting images from one color space to a different
one. Let´s look at the different options one by one:
nColor Profiles
This type of profiles describes output systems with (theoretically)
any number of channels, in real life it´s up to 8 channels. The most
prominent example of such a process is Pantone Hexachrome® with 6
channels.
The author has a dozen or so nColor profiles on his system, besides
"Std Photo YCC Print" which seems to be built-in, only 2 are being
recognized by Photoshop. (Picture 1)
Converting to "Std Photo YCC Print" yields a strange result,
photoshop is obviously not able to interpret this profile correctly.
While the preview still looks good, after the conversion the image is
completely whacked. Admittedly YCC is a color space that never before
had been supported by Adobe products, but even a "normal" 6- or 7-
color space is not being displayed correctly. if such a conversion is
being offered, the image should also be displayed color-correct.
(Picture 2)
Another indication that Photoshop is unable to handle these profiles
is the inability to convert back into a more common color space. Once
in nColor, in the "Edit" menue the options "Assign profile" and
"Convert to profile" are grayed out, and you are stuck in nColor
space. (Picture 3).
As another strange side effect, the channels are numbered from 2 or 3
up and do not contain a selection for all channels. (Picture 4)
Also, the shortcuts "command 2,3,4…" for selecting single channels do
not work any more.
Abstract Profiles
These ICC profiles describe a color edit within the PCS (profile
connection space), normally L*a*b*, and can be used only in
combination with 2 other profiles, an input and an output profile. Not
so in Photoshop 11! Miraculously, abstract profiles can be used stand-
alone. The image remains in the original working space but changes its
look according to the edits in the abstract profile. You can easily
test this on a Macintosh since the so called Quartz filters which are
being installed with the system are abstract profiles. Photoshop
performs 3 transformations here, the first one from working space to
PCS, the second one within PCS and the third one from PCS back to the
original working space. While this seems to be a practical approach,
it bears some uncertainties. When you select a rendering intent, where
is it applied? On the way from working space to PCS, on the way back,
or in both directions? I haven´t found out yet. If you want to apply
the abstract profile on the way from your working space to an output
space, you need to transform another time – you lose flexibility and
each transformation costs image quality.
DeviceLink Profiles
As indicated by the name, a device link profile describes a direct
conversion from one device color space to another one, without going
through PCS. The pros and cons of device link profiles are a subject
for a separate article, only that much: Device link profiles can
improve the quality of a color transformation compared to the usual
profile conversions and they can do useful things like keeping black
as pure black.
So, it´s a good thing that Photoshop can finally handle device link
profiles! The bad news is: They goofed it up! When applying a device
link, the image seemingly remains in the original color space since
the assigned profile remains the same. only after assigning the
destination profile, the image is displayed correctly and can be
retouched or converted again correctly. (Image 5 after device link
conversion, image 6 after assigning the correct destination profile).
That you can only convert from RGB to RGB or from CMYK to CMYK, but
not from RGB to CMYK or vice versa, doesn´t help things either.
Conclusion
While supporting additional types of profile conversions in Photoshop
11 (and only here, not in InDesign or Illustrator) is a commendable
undertaking, it is still in its infancy and leaves room for
improvement. For serious dealing with device link profiles, products
like basICColor demon are still indispensable. Encouraged by the
sloppy implementation of the "new" profile conversions, basICColor
GmbH decided to expand the functionality of demon even more. The
software will offer a correct handling of abstract profiles in
Photoshop as well as in all other programs that allow for selecting an
OS-based CMM, as it does with device link profiles already.
Best regards,
Karl
Am 02.12.2008 um 03:16 schrieb Louis Dery:
Anyone got information or detailed spec about ICC DeviceLink profile
support / compatibility with Adobe Photoshop CS4?
It seems to work only for CMYK to CMYK, not for RGB to CMYK (to keep
neutral RGB on the K plate for example).
Also, be careful to Assign the output profile (used to create the
device link) in order to get accurate preview after the conversion!
Thanks!
Louis Dery
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