Re: [APML] General question

[Alen Koebel <akoebel@rogers.com>]

--- Roland Roberts <roland@astrofoto.org> wrote:

> A common reason to push is also to move the slide
> shadow regions out of the scanner no-man's-land.

That seems to be a major reason for doing it. I've 
got one idea that might achieve something similar
for slides that for whatever reason weren't pushed
but should have been. I think many scanners have
exposure controls where you can (I believe) expose 
the scanning CCD to the light source longer. The
Minolta Dimage Scan Dual III that I use has -2,-1,
0,+1 and +2 settings for this (and "auto" of course,
which I never use on astrophotos). It seems to me 
that if you wanted to push the faint stuff out of 
the CCD's noise floor, then you could simply use a
higher exposure setting on the scanner. I realize 
that since the scanner's CCD is linear, but the 
film's response during initial exposure was not, 
that this is not equivalent to pushing the film 
during development. It will need curve correction
to compensate for the linearity difference at the
low end, and it will blow out the highlights even 
more than pushing would. But the latter effect 
could be fixed by combining scans at two different
exposure settings. It's a lot of work, but this 
could capture more of the faint stuff that ended 
up in the highly non-linear toe region of the film,
thus saving an otherwise un-promising image. 
Comments?
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