[filmscanners] RE: Pixels and Prints

["Austin Franklin" <austin@darkroom.com>]

Hi Paul,

> > Lower noise?  What you are calling lower noise is dubious.  "Perceived"
> > lower noise does not mean higher fidelity.  How do you know it's lower
> > noise?  Have you actually done a comparison of it to the original image
> > scene to see what was noise and what was not?  The Bayer pattern
> > reconciliation introduces substantial noise, it has to by nature.  Also,
> > lack of detail make it appear as less noise.  Again, cartoons
> > appear to have
> > very little noise, and they have no detail.
>
> I may regret getting involved in this discussion, but it's hard
> to let this
> pass. In real life, you don't have to compare a digital image to the
> original scene to know what's noise and what isn't.
> Blue sky is about as
> noiseless a source as you can find, so any noise you see is in the capture
> process.

Blue sky is hardly noiseless.  That doesn't mean that there can't be other
sources of noise, some more significant than others, of course, but to
assume that there is simply no noise in a blue sky is, IMO, a bad
assumption.  Do you have any actual data to back up this claim?  I've
analyzed a lot of "sky", and certainly wouldn't make a generalization like
that.

> Also, a Bayer pattern interpolator doesn't introduce noise, unless it's
> processing an image that already looks like noise, and it can't find
> anything coherent to do edge detection on.

Of course the Bayer pattern reconciliation introduces noise, it has to by
it's very nature.  Any time you are interpolating, you have a high chance of
introducing noise.  Noise is, in this case, is introduced in both the
spatial domain and the color domain.  No field in real life (even sky) is
entirely "even", where all the values are exactly the same (or precisely
linear) across a significant space.  There are many different interpolation
methodologies, of course, some better than others (and I've designed quite a
few), but any interpolation algorithm used for Bayer pattern reconciliation
will introduce noise.

Regards,

Austin

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