Re: How to force profile conversion in Photoshop?
Re: How to force profile conversion in Photoshop?
- Subject: Re: How to force profile conversion in Photoshop?
- From: Klaus Karcher <email@hidden>
- Date: Tue, 09 Dec 2003 17:20:05 +0100
- Organization: schrift & form GmbH
Chris Murphy wrote:
On Dec 8, 2003, at 4:08 AM, Klaus Karcher wrote:
If you try to do it in 16 bit, you need 4 Steps:
(8bitCMYK -> 16bitCMYK -> 16bitLab -> 16bitCMYK -> 8bitCMYK) and up to
Version 7 you also lose transparency and layers (maybe not in CS?).
Any suggestions for a simpler workaround?
Script it and assign to a function key. If the source and destination
profiles are differently named (external and internal) then Photoshop
will use them; you won't get a null conversion.
As I mentioned yesterday, this won't work in Photoshop 6-7
(maybe in CS?):
Up to Photoshop 5.5, it was possible to force conversion by unsing two
copys of the same profile with different internal names - but since
Photoshop 6 even this workaround won't help anymore.
(the Conversion does nothing -- it even does't say that it does nothing!)
If all you're looking to fix is ink limits, this is probably not the
best way to do it if the destination is a press. You should probably
consider using a DeviceLink profile to restore an appropriate ink limit,
while preserving as much unique channel behavior as possible.
How can I create such kind of DeviceLink profile?
And at the point in time you care about finalizing ink limits in the
image, why do you care about preserving layers and transparency? I'm
currently not thinking of a case where compositing can occur after color
management, and for it to be successful because after compositing you
will get color shifts and even changes in ink limits if it were done in
CMYK.
I often have to work with layered CMYK files delivered by customers. In
many cases they are intended to be used in European Sheetfeed Offset,
but contain either no profile or the wrog one (SWOP, Photoshop 5
default, ...).
Often I have to guess the primary printing process as well as the
intended appearance. If I am in the lucky situation that the intended
appearance is achieved simply by assigning the supposed output profile,
but the image does not meet the required black generation and ink
limits, IMHO the indicated policy is to convert the image *from* this
profile *to* this profile - but this is what Photoshop forbids without
any comment, even with internal differently named profiles!
It also happens that delivered files were alredy printed before and have
to be modified partially for a new edition or composed with other CMYK
images for a new purpose.
There are as many reasons to use layers in CMYK as in RGB or any other
Color Space, e.g. the need for
- documenting the changes on CMYK images
(by keeping them on different Layers)
- making them reproducable or transferable to other images
- making them undoable (also patial by adding masks)
- create intermediate versions (by changing the opacity of a layer)
Another frequently appearing requirement is to achieve a given CMYK
value (like 100/80/0/0) in order to obtain a seamless transition to
adjoining text or vector elements.
And sometimes it's just practical to keep different versions in one File.
As long as adjustment layers and modes like "multiply" or "color burn"
are used with care, the risk to exceed the ink limit is quite small. By
a similar way it's possible to preserve the requested black generation
in the most cases widely (and if not its's just another reason for a
CMYK 2 CMYK transformation ;-).
Fortunately, all our scans have been stored, color corrected and
archived in the thoughtful, media independed LabLH color space for a
realy long time. But unfortunately this great color space is neither
vendor independed nor supported in Adobe Products, and meanwhile not
even available in current Heidelberg products.
Nevertheless, as you can validate on the examples above, there are many
situations in my everyday work where it's still advisable to keep files
in CMYK and sometimes it's more advantageous to re-convert parts or
single layers then transfering everything to a media independed working
space. And I think it will take at least several years until this
situations will disappear from everyday life.
Regards, Klaus Karcher
P.S.: ...and please excuse my clumsy english ... i'm working on it ;-)
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