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Chris Murphy wrote:
You're making it sound like there is no difference between RelCol and
AbsCol in both an ICC v4 soft proofing context, as well as a Photoshop
context.
As I said, I can't speak for Photoshop, but in ICC V4, there is no
difference between RelCol and AbsCol for display profiles,
because ICC V4 mandates that a display profile have a media
white point tag the same as the PCS, and it's the difference
between the PCS white point and the white point tag that
makes a difference between RelCol and AbsCol.
There is white simulation.
I'm sorry, what's that ? There is no "white simulation" intent
or function in the ICC standard. There are just the usual 4
intents.
> It's just predicated on the end
user being adapted to display white, and that happens to work whereas
when it's predicated on the end user not being adapted to display white
it doesn't work.
I'm not following what you're saying I'm afraid.
Actually it didn't provide it because there was no specificity as to
the level of adaptation of the end user.
It doesn't need to have such a thing. The intents provide a certain
mechanism. The mechanisms may serve certain functions depending on
the adaptive state of the users. Reducing the mechanism for
display profiles from 4 to 3 doesn't make a shred of sense to me,
since it reduces the scope of potential functionality. Perceptual
is often well suited to a situation where the viewer is assumed
to be fully adapted to the white point. Absolute is well
suited to the situation where the user was not assumed to
be fully adapted to any one white point, hence it's
broad use in hard proofing. Nothings is fundamentally
different about displays in that regard though.
> No matter what, something had
to be assumed because it wasn't specified.
It doesn't have to be assumed by the ICC standard. It's up
to the application and the user to make choices from the
available mechanisms in order to serve a particular purpose.
> And what most
implementations did was assume the end user was not fully adapted to
display white, and those implementations yielded inferior results.
So you say, and I don't agree with you. Irrespective of whether this
is the case though, I can't fathom the logic of folding what was a
distinct and potentially useful intent (Absolute) into being identical
to Relative for display profiles.
When you check "Simulate Paper White" it is using Absolute Colorimetric
rendering to the display. The on-screen result is the same for a v2
display profile, or a v4 display profile. And if you do the conversion
using an ICC v4 display profile, and AbsCol using the Apple CMM with an
AppleScript you get the same result as well.
But is this the same, or different to using a v2 display profile and the
Apple CMM and AbsCol ?
Graeme Gill.
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