Re: scanner profiling (again)
Re: scanner profiling (again)
- Subject: Re: scanner profiling (again)
- From: Graeme Gill <email@hidden>
- Date: Wed, 17 Dec 2003 23:42:27 +1100
Armand Rosenberg wrote:
To repeat: I have a pretty accurate exposure and processing is also
reasonably consistent (with positive film). Then I would think that wp
and bp should be reasonably consistent between target and image. I can
understand small deviations, but not major changes.
The classic explanation for such things, is that something about
the device isn't consistent between its use in profiling, and its
use for real work. For instance, settings set differently between
scanning the IT8 chart, and scanning real work. Another type of
possibility may be that there is some sort of "automatic exposure"
feature being applied between the scanner and the pixel data,
that makes the response depend on image content.
Any such device behavior inconsistency throws the whole
ICC approach out of whack.
A careful set of experiments should reveal what's going on.
For instance:
Setup scanner to reference.
Scan IT8
Scan "real world" image
Scan IT8 and real world image together.
Make ICC profile from individual scan of IT8, and use it to convert
all 3 scans to your desired working space.
Make ICC profile from the combined scan of IT8 and the image, and
use it to convert all 3 scans to your desired working space.
Report results (ie. which are the same, which are
different and in which direction).
Graeme Gill.
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