Re: filmscanners: Image alignment/registration

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

Michael Moore writes ...

> Shaf: I think that what the question intended is the same holy grail
I am in
> puruit of... that of being able to make TWO or more EXPOSURES at the
time the
> picture is created... in the camera... one shot for shadow, one for
mid tones,
> one for highlights, all without moving the camera... then making
scans of each
> exposure, and then combining these three in Photoshop... I have an
article on
> this technique that I have misplaced, but I know it is possible.. I
have also
> seen the section of Caponigro's book, which I highly recommend...
and he
> specifically takes you step by step through his creation of a long
tonal range
> color landscape of Death Valley.... so the question is... How do you
> accurately register multiple scans of different negs of the same
subject?

    Different negative frames are are different issue.  That is, I
thought the initial post was about acquiring as much information
possible form the same negative ... which given the latitude of
negative exposures should be possible ('cept for extreme ranges, of
course).
    Let me ask if your "holy grail" is with respect to a scanner which
can only deliver 8bits/channel?  If so, then 'yes' you need to scan
multiple times before you can "blend" the information gained from each
into what you're satisfied with.  On the other hand, if your scanner
can deliver more than 8bits/channel, then there is "probably" enough
info there for not needing to scan multiple times.  Take a
underexposed backlit subject ... in 12bit depth, there is probably 100
levels of luminosity available in the underexposed subject ... plenty
for a brightness/contrast/gamma 'levels' adjustment.
    Granted ... the information in the shadows, even in highbit space,
needs to have the noise removed with multiple passes.  Much of this
capability is why I bought my particular scanner.  BUT, I also need to
read up on your references ... if you find them please pass them
along.

shAf  :o)