Following standards (rendering intents)
Following standards (rendering intents)
- Subject: Following standards (rendering intents)
- From: "Andre Schützenhofer" <email@hidden>
- Date: Mon, 10 Dec 2001 21:17:57 +0100
Please let me point out some issues from my point of view, regarding those
statements Henrik Holmegaard made. No need to bash you. With most you've
said I totally agree, -
If Black Point Compensation is a non-standard processing implementation,
then it is surely right as diplomatic default for the source to output
step, even if it just as surely wrong for the output to destination step,
because applying it here leads to a soft proof and a proof print which do
not match the output print. This is the current problem in Adobe software.
If BPC is checked in the color settings dialog, the softproof settings are
correct. The only difference respective BPC switched off is that selecting
rel col as priority applies BPC automatically, as wished. I can see no case
in which BPC influences the softproof settings in a wrong way. For CMYK to
PCS direction PS always uses relative lightness (L = 0-100), except for the
case black ink or paper white is checked which rescales lightness to the
deepest visual tone (total ink limit) or/and paper white regarding the
specific characteristics of the destination profile.
If a CMYK file is opened it works the same, if preserve numbers is checked
the softproof shows the file itself. And if preserve numbers is not checked
the softproof simulates the look of the file after transformation with the
chosen priority, in the case BPC is checked in the color settings dialog
with BPC if rel col is selected.
So I think there are no problems using BPC within PS. And there is another
thing I find interesting: in comparision with the perceptual and
colorimetrical intents in Adobe standard profiles there are marginal
differences in the transformation result (BPC on), so it seems perceptual
LUTs are build like rel col with BPC. - Good work :-)
But is it doable at this stage to tell newbies that they should use RelCol
BPC for SourceRGB to OutputCMYK in a manual conversion, revisit the Color
Settings dialog to uncheck BPC, and then select RelCol in the Print dialog
(a three step workflow)? Personally, I don't think so because pulling a
proof print becomes so very complex compared to recommending BPC off and
Perceptual for Output followed by RelCol for the proof print and soft proof
I think its not this difficult, all we have to do is check BPC and nothing
can be done wrong. The bigger problem is to end up with a correct softproof
by using abs col, but this is a different matter.
What would be really cool is to let the operator decide which kind of
default intent should be generated, dependent on the requirements the
workflow needs. Which means for instance the smaller the gamut the more
perceptual rendering is required or something like that, on the other hand
if the destination is big enough to contain most of the source colors, rel
col BPC is more suitable.
And let's open up BPC to the rest of the colormanagement world.
And yes, this technology has made things much easier then they were. And who
has arguments that this will never work??? Did they ever really tried?
- Andre Schuetzenhofer
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