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[filmscanners] Re: Newish Digital Tech

"Paul D. DeRocco" <pderocco@ix.netcom.com> wrote:

But _any_ pixelated sensor will alias if it doesn't have a diffuser in front
of it. The point of the Foveon chip is that the aliases are the same for all
colors, so you don't get color moire from a monochrome texture.

Exactly. All Foveon does is hide the artifacts so you can't recognize them
when you look at the image. In the res test charts, it "resolves" a 9-band
image as 9 bands for some frequencies, 7 bands for other frequencies, 5
bands for other frequencies; all with the same contrast. This is seriously
unacceptable. Without an anti-aliasing filter, it's not a camera, it's a
random data generator.

It's certainly true that digicams are slowed down by the limited speed of
the storage medium, and this is exacerbated by increasing the file size.
However, the really good Bayer decoding algorithms, like Variable Number of
Gradients, are very CPU intensive. When I decode the raw files from my
Minolta DiMage 7 using their PC utility, or a couple other PC-based programs
I have for this purpose, it takes several seconds to decode them on a 1.7GHz

So? Most serious photographers take RAW images and postprocess on their
PC/Mac. Several seconds per image is no big deal. Also, special-purpose
hardware is always orders of magnitude faster than general-purpose hardware.

 The camera itself is capable of doing the conversion, plus JPEG
compression, in much less time, so I suspect the camera's using a simpler,
inferior algorithm (although I haven't noticed any artifacts).

Again, all the cameras use special-purpose hardware. Hardware is cheap and
fast. The processing time issue is completely bogus.

> Color rendition is problematic in the SD9...

That may just be an implementation problem with that particular camera.

And it may be an inherent problem with the Foveon technology. It's Foveon's
job to prove that it works, not ours to appologize for Sigma.

David J. Littleboy
Tokyo, Japan

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