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     áòèé÷ :: Filmscanners
Filmscanners mailing list archive (filmscanners@halftone.co.uk)

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[filmscanners] RE: Pixels and Prints



Hi Paul,

> when you look at the sky, you don't.

How do you know you don't?

> But the point is that
> the amount
> of noise you get in the digital image depends upon the hardware, so it
> obviously can't all be actual noise coming from the sky. My old
> DiMage 7 is
> _very_ noisy, even at ISO 100. My Nikon LS-2000, scanning
> Kodachrome 25, or
> for that matter E6 slide film, has a lot of noise, presumably from film
> grain, too. My Canon 10D has much less noise in the final result.

But that doesn't mean that every combination of film/scanner has noticeable
noise generated by these things in sky regions.

> Noise is random

Noise does not have to be random.  It can be random, or deterministic.  It's
still noise.  Anything that decreases fidelity is considered noise.

, meaning that if you repeat the process, you get different
> answers. If you repeat the Bayer interpolation on the same raw
> data, you get
> the same answers. That's not noise, it's distortion.

Distortion is noise.  I really don't care what you want to call it, and I'm
surprised you're arguing semantics here...instead of arguing the points.

> What's more, for
> real-world images, with the sort of detail on which people would
> recognize a
> loss of resolution, e.g., sharp edges, modern Bayer algorithims
> _correctly_
> interpolate, producing what looks right to the eye.

No, they don't %100 "correctly" interpolate the information %100 of the time
(unless you're talking about someone with very diminished vision).  Edges
aren't always "sharp", and "sharp" is really an amorphous term as well.  I'd
love to see some actual data you base this claim on...having written quite a
few Bayer pattern reconciliation algorithms, I know it's just simply not
true...and we did experiment with full three color data to see how well the
algorithms worked.  "Looking right to the eye" has nothing to do with
fidelity of the image.

Regards,

Austin

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