[filmscanners] RE: Pixels and Prints

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

> From: Austin Franklin
>
> How do you know you don't?

I dunno. How do I know this isn't all a dream?

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

I assume drum scanners do much better, but they're a heck of a lot more
expensive than a Canon Digital Rebel.

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

This is not a semantic issue. Noise is _fundamentally_ different from
distortion. For some purposes, distortion can be analyzed as though it was
noise, but only in the case of things like quantization, where the spectrum
of the distorion is noise-like.

But the point here is that if a Bayer pattern generated "noise" then it
would be filling in the pixels in some unpredictable, and therefore
ultimately useless, manner. But it doesn't. On the sort of image detail that
matters, modern Bayer interpolation algorithms do the Right Thing, and do so
consistently and effectively.

So while it's theoretically possible that a Bayer camera will miss a red dot
on a white wall, because light from the red dot happens to fall only on a
red pixel, who cares? Qualitatively, Bayer sensors work extremely well, so
it's closer to the truth to say that a six-million sensor Bayer chip
produces a six megapixel image than to say that it really only produces a
1.5 megapixel image.

--

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

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