[filmscanners] RE: IV ED dynamic range

["Austin Franklin" <darkroom@ix.netcom.com>]

> > well I very seldom use 12 bit scanning, perhaps this
> > is a problem ?
>
> Yes, it is a very big problem!  If you don't scan at the highest available
> bit depth, trying to get detail out of shadows and highlights is almost a
> complete waste of time, and will often give bad results even when
> it works.
> You _must_ scan as deeply as possible if you plan to expand shadows or
> highlights.

Hi Anthony,

That's not how scanners work.  They ALL DO SCAN at the highest bit depth
they have...ALWAYS.  The 8 bit file will contain the FULL range available on
the film, if the setpoints are set correctly.  When you choose high bit
data, you do not set any setpoints, or adjust any curves...it's simply raw
data.  When you choose 8 bit data, you set the setpoints, and the tonal
curves (which can be used to expand the highlights and shadows as you say
above), and the scanner does the tonal curve adjustment to the high bit
mode, and maps the setpointed range/tonally remapped data into 256 tones.
So, you still get the full range the film has...and can have your highlights
and shadows as expanded as you like.

The human eye has been shown to be only able to discern 100 graytones, and
16M color tones.  This means grayscale of 8 bits, and color of 8 bits/pixel
(24 bits total)...so any "extra tonal detail" will not be able to be seen
anyway.

Austin

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