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[filmscanners] RE: LS2000 Shadow Detail problem



Jerry writes ...

> ...
> ... I ran across a curious problem with the Nikon LS2000
> losing shadow detail that was captured in the scan, but
> not retained when color management was used.
>
> I've detailed it with pictures and descriptions of my
> methodology at:
> http://www.astropix.com/CURIOUS/CURIOUS.HTM
> ...

  This is one reason I do not use Nikonscan (even the latest versions), and
use Vuescan instead.  That is, I notice this "effect" not even in shadows
... what I saw was posterization in skin tones!  Understand that the Nikon
profiles for the scanner are essentially look-up tables.  The CLUTs cannot
contain a value for every RGB=>RGB*, and while I believe intermediate RGB
values are supposed to be assigned some interpolated value, I don't believe
the Nikon software does this very effectively (accurately).  You can see
examples of this same effect if you soft-proof a color gradient with some
printer profiles, i.e., you'll see some banding.  It is impossible to
understand Nikon's method exactly, but the end product implies something
like this is going on.

  Vuescan's approach to profiling a scanner is to assign it a matrix-type
"color space" ... which isn't entirely as accurate, but its transitions are
smooth, ... and more importantly, such color artifacts are correctable.

cheerios ... shAf  :o)
Avalon Peninsula, Newfoundland
www.micro-investigations.com (in progress)

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