Re: Is this a scum dot?
Re: Is this a scum dot?
- Subject: Re: Is this a scum dot?
- From: bruce fraser <email@hidden>
- Date: Wed, 13 Nov 2002 19:39:22 -0800
At 2:14 PM +1100 11/14/02, Graeme Gill wrote:
bruce fraser wrote:
It sounds like the scanner profile is the culprit. What happens when
you convert scanner RGB 255, 255, 255 to LAB?
There are certainly many ways a profiling system might create
scanner profiles, but given the way I understand scanner profiles
are normally created and used, I certainly wouldn't expect anything
useful to be gleaned from the answer this question.
Graeme,
If the scanner profile translates RGB 255,255,255, relcol, to
something less than L*100, it is by definition broken.
Typically, scanner testcharts record the actual media white of the
target in the target description file, and profilers try to reproduce
that white in the profile. Different profilers do different
normalizations, but it's unusual and generally undesirable to capture
the white of the target as L*100, or for that matter to set the
scanner to produce RGB 255 from the paper white (or filmbase+fog).
It's entirely likely that a scanner will, at some point, be called
upon to scan something brighter than the white of the calibration
target...
Bruce
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