[filmscanners] CCD flexibility re: multiple concurrent scene exposures.

["Dieder Bylsma" <scanners@spacemoo.com>]

Just wanted to figure out if my reading of the reasons why this is
not currently possible at the same time.

Specifically if we have either

a) a filmstrip

or

b) a digital back

is it currently impossible to have, in a single scan/scene capture,
multiple sensitivities of the CCD/CMOS sensor arrays?

Ideally this would offer the opportunity in high contrast situations
(i.e. wedding photography, etc) where a digital sensor would be
suitably (in)sensitive to the high white values of a scene's
components (bridal dress) and sensitive enough to record shadow
detail.

I guess what I'm talking about is multiple exposure bracketing in the
same picture. Given a 16 bit range for independent RGB channels, it
should be possible to produce a picture of utmost range without
clipping. As it is, given a negative/slide which has lovely detail in
the bright areas (be it a bridal dress, or clouds etc) and detail in
dark parts of the shadows, the only way to do it as far as I can see
is either by re-scanning the area for both extremes (a la Vuescan's
double-scan/long exposure technique) or to take two pictures.

My guess (without any substantive knowledge of the mechanics of the
sensors) is that the individual sensors in an array can't all be read
individually and the exposure time has to be the same across the
whole sensor array before the array as a whole can be 'closed' and
made ready for data transmission. Is this correct?


Dieder

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