[filmscanners] RE: Density vs Dynamic range

["Austin Franklin" <darkroom@ix.netcom.com>]

Hi Laurie,

> The first point of confusion in your discussion with Austin appears to be
> that what you are referring to as "dynamic range" he is referring to as
> "density range" or that you are using the two terms synonomously
> while he is
> using them as naming two different concepts.

Dynamic range is, in our case, (dMax - dMin) / noise.  Density range is
simply dMax - dMin.  Dynamic range is the number of discernable values
within a density range (in our case).  Density range is simply the max
density value you can get minus the minimum density value you can get.

> For instance, if I may take
> the liberty to put words in his mouth, take the statement:
>       "If we double the number of bits (possible values) that doesn't
>       increase the dynamic range of the scanner, only it's
> ability to represent
>       accurately the value coming from the CCD."
>
> I think apart from maybe disagreeing with "the value coming from the CCD,"
> he would say that what you are saying should read:
>       If we double the number of bits (possible values) that doesn't
>       increase the DENSITY RANGE of the scanner, only it's
> ability to represent
>       accurately the DYNAMIC RANGE value CAPTURED AND DIGITALIZED by the
>       scanner's analog to digital converter.

Well, you HAVE to increase the scanners dynamic range for more bits to
increase the ability to represent accurately the value coming from the CCD,
assuming, as I've said that the number of bits was matched to the dynamic
range of the CCD in the first place.

Doubling the number of bits also does not increase the density range of the
scanner, and it also doesn't increase the ability to represent accurately
the dynamic range (as I said above).

> (Austin, if you are reading this and I am putting the wrong spin on it or
> words in your mouth, please feel free to correct me.)

Yeah, I think things are being confused a bit (sic ;-)...  Too bad ;-(  It's
really quite simple.

Regards,

Austin

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