Re: colorsync-users digest, Vol 2 #398 - 12 msgs, Of black point compensation (short version -:))
Re: colorsync-users digest, Vol 2 #398 - 12 msgs, Of black point compensation (short version -:))
- Subject: Re: colorsync-users digest, Vol 2 #398 - 12 msgs, Of black point compensation (short version -:))
- From: lasse seppala <email@hidden>
- Date: Wed, 4 Jul 2001 00:34:07 +0300
Message: 8
Date: Tue, 26 Jun 2001 18:37:17 +0200
To: email@hidden
From: Henrik Holmegaard <email@hidden>
Subject: Of black point compensation (short version -:))
Cc: email@hidden
Or to put it briefly, because
a. Perceptual is white point and black point relative,
b. Relative Colorimetric is white point relative and black point absolute, and
c. Absolute Colorimetric is white point and black point absolute.
Then to separate with Relative Colorimetric, the black point should
be relative and not absolute, which is what Black Point Compensation
does.
And to soft proof and proof print with Relative Colorimetric, the
black point should be absolute as otherwise the lighter offset black
gets mapped to the deepest black of the monitor and proofer, which is
what Ink Black does. The implementation for Adobe tools until PS6 was
to soft proof with relative white and relative black, dressing up the
grayish black of the printed page in more eye-catching designer black
-:).
Simply saying to separate with Perceptual and proof with the standard
implementation of Relative Colorimetric with absolute black (: no
BPC) works every time. And is also easy to understand, no?
--
Henrik Holmegaard
TechWrite, Denmark
I agree with these points except for softproofing. For softproofing
you should use the rendering intent (perceptual<>relativ) you are
going to use for actual separating. So you can get the best softproof
setting manually View_ProofSetup_Custom_Profile(cmyk-profile you are
going to use)_Intent(you are going to
use)_Simulate(PaperWhite/InkBlack/Preview checked).
You can test it easily making a couple of copies of the file (good
and saturated picture) and separeting them with differennt intents
(perceptual/relative BPC), softproofing CMYK manually as above. Then
you softproof RGB/Lab -file as above (with two views
View_NewView...), other view vith perceptul, other view vith
relative. Relative-CMYK should match relative-RGB-view and
perceptual-CMYK should match perceptual-RGB-view. Paper white -box
checkink makes softproofs look even more "grayish", but it can
simulate paper color and tonality with that paper quite well.
With these settings you can get a quite close softproofs with PS6 assuming:
1. You have good quality profile for a good monitor and profile
(good) for press/paper-combination (hopefully not drifting so much...)
2. You have good working conditions - especially lightning (5000K,
dim, no reflections)
3. You have dimmable booth stand to match monitor color temperature
and ligtness with final prints
4. You have an open mind to accept the fact that monitor is no paper
and vice versa. Don4t expect 100% matching, but quite a good
(especially) tonal response
For future use you can save these settings with descriptive names and
you are one click away from softproofing (with different views for
different intents/presses) picture before actually separating file.
This is very important especially when you have a color server and/or
you are using a profiled press/many presses with different papers.
Lasse Seppdld