Re: Is there such thing as a wide gamut CMYK workspace?
Re: Is there such thing as a wide gamut CMYK workspace?
- Subject: Re: Is there such thing as a wide gamut CMYK workspace?
- From: "Stephen Marsh" <email@hidden>
- Date: Mon, 11 Feb 2002 02:24:12 +1100
Paul Schilliger writes:
>
Just for the sake of curiosity or for the anecdote, I am curious to
>
know if there is a wide gamut profile for CMYK. I
>
had been told that scanning in that space gives a better control
>
over black for Lambda output.
Bruce Fraser writes:
>
While it would certainly be possible to create a synthetic wide-gamut
>
CMYK space, the Lambda is a true RGB device, so any additional
>
control the black plate seemed to offer would be entirely illusory...
Stephen Ray writes:
>
As for "better control over black" this is probably suggested by someone
more
>
experienced in color-correcting CMYK than they are at RGB files. That is
fine
>
but they should really soft-proof thru the Lambda profile to see where the
>
surprizes might be...
This is an interesting topic, which has popped up before on other lists.
I agree with Stephen Ray that to a CMYK user - having access to a light
black plate such as in Photoshop's built in UCR or as in a Light GCR type
separation can be beneficial to some types of image content correction. But
even users who never go to CMYK can benefit from having a black plate -
since it provides an editing possibility that does not exist in RGB or LAB
(mostly for sharpening and targeted shadow detail adjustments). There are
other reasons why the CMY channels can be beneficial as well, but I see the
most benefit to a skeleton black plate over the other channels for a
synthetic wide gamut correction space.
I also agree with Bruce Fraser that this is possible and that the Lambda
would not care for any wide gamut CMYK space - you would still need to
convert to the correct Lambda output profile, since the separation data in
the wide gamut CMYK space would not be used. But this does not mean that
once an image had been tweaked in a 'idealised wide gamut CMYK' space that
those edits would be ignored - the benefits gained would be translated into
the final output space (just like edits performed in one mode get
transformed into another mode).
Yes there is a wide gamut CMYK profile - which attempts to make the RGB >
WGCMYK > RGB move as lossless as possible, so that the black channel can be
edited for more natural effect than by sharpening via selections or for
targeted luminosity or shadow detail enhancement.
Some users are playing with RGBK profiles and separation tricks to take
advantage of skeleton black without loosing their wider gamut.
The RGBK approach seems more practical than WGCMYK, mostly it is a more
intuitive principle with no new custom gray balance rules to figure out and
it is easier to edit in.
There are quite a few problems with the WGCMYK profile that has been
developed - with the biggest being that the black generation is too heavy
for any practical use and gray balance is totally screwy, as well as the
move being far from 'near lossless' and often doing more harm than the
supposed benefits gained (it varies on different image content).
I would not use this WGCMYK profile for production work - I have only
briefly played with it when the subject first came up, and the author does
state that it is a work in progress - so with caution in mind:
http://geigy.2y.net/DigPhoto/WideGamutCMYK/Default.htm
I do not use this profile and do not agree with the WGCMYK principle - I
much prefer the RGBK profile or editing technique idea if it could be made
near lossless (the result of using RGBK would have to outweigh the
conversion, just as in LAB edits).
And two points to keep in mind:
i) Some (but not all) images do not greatly suffer from conversion to CMYK -
it is amazing how many deep shadow areas are often out of gamut.
ii) And if you had no choice but to output a SWOP or even newsprint
separation on a wider gamut device (nor RGB or original to rescan) - it does
not mean you are stuck to the limited gamut of the CMYK original. You will
not get the original RGB wider gamut colours, but you can apply some linear
curve edits to steepen the AB curves in LAB (without moving the midpoint) -
before the file goes to RGB (less than ideal CMYK > LAB linear colour edits
>
output RGB). With LAB it is all too easy to increase gamut.
All colour spaces and channels have something to offer - which is why I
would like to have access to HSB mode again in Photoshop, which has been
missing for so long. I like the LS curve editing option on some CreoScitex
scanners, and having HSB mode again in Photoshop would offer these and other
possibilities (I never really found out why they were dropped).
Just my $0.02
Regards,
Stephen Marsh.
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