[filmscanners] RE: Newish Digital Tech

["Paul D. DeRocco" <pderocco@ix.netcom.com>]

> From: Karl Schulmeisters
>
> That's not how the Foveon chip works.  There are no filters. They
> are taking
> advantage of the fact that different light frequencies have
> different depth
> penetrations into silicon.  This is likely in part what is
> causing the color
> rendition problems.  Essentially there is not going to be as clean a
> differentiation between the amount of light at the R,G and B
> sites, and they
> are relying on subractive calculation to compute the R and G
> values.  Since
> the photo-electric effect is a statistical (quantum) phenomenon, I can see
> this being a source of sensor error.

Yes, I've read the Foveon patent. Just because there aren't separate filters
doesn't mean that the light doesn't get filtered. It's happening in the
semiconductor layers. There are indeed three outputs, and they respond to
the range of visible frequencies as I described.

You seem to imply that it's desireable that there be a sharp separation of
light into red, green and blue bands, when indeed that would result in
terrible color rendition because it would make certain wavelengths that look
different to the eye produce the same numeric output. It's important that
the three spectral responses have overlapping slopes, so that different
wavelengths will produce different outputs. The fact that some subtractive
calculation is involved doesn't matter--heck, there is much more elaborate
arithmetic going on in a Bayer decoder.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@ix.netcom.com

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