Re: filmscanners: This Gamma Thing...?

["shAf" <michael@shaffer.net>]

Tom writes ...

> Thanks for the explanation. Now I just need to get some kind of idea
of a
> good value for gamma. Windows defaults to 2.2. My scanner software
defaults
> to 1.4. If I change the scanner software to gamma=2.2 images look
WAY too
> bright... Why the difference?

    We need to be a bit careful about what your scanner's gamma (1.4)
means.  Is it the scanner's "absolute" gamma, or is it a request to
modify the data's gamma by a relative amount ("relative" gamma).  It
is difficult to know and answer your question.
    My "guess" is it is a relative gamma parameter.  It asks you "how
much do you want this scanner's data to be changed", and it is not
asking what your Windows gamma is.  That is, if you imply 2.2, then
you imply "2.2 on top of 2.2", which will be way too much.  If you
imply 1.0, then you mean don't change a thing, and you simply put your
scanner data in Windows' 2.2 gamma.  In between is probably some
optimal value ... it may be 1.4 ... but then your scanner software
probably had no idea (exactly).  You need a way to match what you see
on your monitor to what it's supposed to look like ... eg, light table
for your slides, or good proofs for your negatives.

shAf  :o)