Re: Photoshop 6 Duotone Mode, Working Spaces & Profiles
Re: Photoshop 6 Duotone Mode, Working Spaces & Profiles
- Subject: Re: Photoshop 6 Duotone Mode, Working Spaces & Profiles
- From: Thomas Knoll <email@hidden>
- Date: Wed, 20 Mar 2002 08:21:15 -0800
Thomas, firstly - thank you for your interest and response. How about
answers to these questions, now that the full depth of the issue has been
noted:
* Why do both CMYK and Spot WS set-ups in ver6 impact on the Duotone file
created with custom colour picker, why not one or the other - why
'calibrate' twice on the same image?
The CMYK working space in version 6 will only affect the duotone
display if one or more of the colors defining the duotone inks is a
CMYK color. The RGB and Gray working spaces can also affect things
if you pick the duotone colors in one of those spaces.
* Why is it that default colour book library colours are NOT linked to the
CMYK WS and are only affected by Spot WS settings? I guess this is the part
of your answer about how things changed in ver6 from 5.
Some default book colors in are native CMYK, some in Lab, and some in
a mixed Lab/CMYK hybrid (e.g. most Pantone books). The mixed
Lab/CMYK books behave like Lab as far as duotone display is concerned.
* How does one stop the Duotone colour picker settings from changing, if you
use custom picker builds - and the file is opened with different CMYK
settings? As you say, CMYK should not matter in ver6 - BUT IT DOES.
Don't use spot colors defined in CMYK space. Pick the colors in Lab
space instead.
* How do you 'tag' the CMYK and or Spot WS to the Duotone file, since this
has a critical impact on opening the Duotone file and converting to other
modes? EPS, PDF and PSD Duotone don't seem to support ICC methods of knowing
about the colour characteristics of the file.
You can't. Photoshop does not support ICC tagging of duotone files,
mostly because there is not such a thing as a "duotone" ICC profile.
The spot ink dot gain profiles used the color settings dialog is
really just gray scale profiles, and encode only one tiny bit of the
information required for an accurate duotone display. Ideally a
duotone ICC profile would have separate dot gains for each color,
information on the Lab values of each ink color, information on how
the colors overprint in all combinations and percentages, etc.
Just embedding the spot ink dot gain profile would not solve the
problem, since the ink colors can be defined also be specified in
CMYK, RGB or Gray spaces, requiring up to 4 existing ICC profiles to
be embedded. I think the resulting profile mismatch dialog with four
embedded profiles might be somewhat confusing to the user.
In any case, duotone files should be files that you intent to output
as duotone files, and are thus already in device space. The working
space profiles only affect the preview, not the duotone output
plates. The preview simulation of duotone files is only approximate
at best. Duotone mode were never intended to act as an editing mode
for files that will primary be output to a CMYK or RGB printer.
Expecting accurate proofs of duotone mode documents on CMYK or RGB
devices is expecting far too much from Photoshop's duotone mode, give
the very limited amount of information it has about ink interactions.
* Why is it that Photoshop is both the inset and dotgain, you only mention
dot gain.
Photoshop is using total reproduction process dot gain, e.g. what 50%
ink in the digital file ends up printing as on the final press run.
How this total dot gain breaks down between various steps of the
reproduction process is completely irrelevant as far as Photoshop is
concerned.
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