[filmscanners] Re: Dynamic range

["Todd Flashner" <tflash@earthlink.net>]

Todd wrote:
> These values can be obtained from testing, and the bit-depth/resolution
> within that range is immaterial to the DEFINITION of DyR. It may be material
> to the values you will measure in testing, but it is immaterial to the
> definition/formula.
> <<<<<<<<<<<<<<<

David J. Littleboy wrote:
> Yes, I think, sort of, maybe. If you are looking at the analog signal prior
> to the A/D converter.

Yes, I am, because that is where the DyR will be captured. The bits are just
there to represent the DyR digitally, no?

> But the bit-depth is material to the scanner user, since if it is
> inadequate, then the quantization error will be larger than the noise, and
> value of the minimum discernable signal rises. If the bit depth is
> excessive, then the noise becomes the limiting factor, since the device will
> return a distribution of random values for a given density on the film. If
> you start throwing away excessive bits, the range of the distribution of
> those random values will get smaller and smaller...

I think I agree with this - not sure about the last line, but I'll take your
word for it. HOWEVER, this is where this conversation often bogs down and it
is simply immaterial to what DyR is, and what DyR is is what this
conversation is really about. I believe the only way to really get at what
DyR is is to discuss it in the analog domain, (though I'm not sure how to do
it since most references seemed geared to digital applications). After we
understand DyR then we can look at how it applies to scanners, if we still
care to.

Todd

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