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[filmscanners] RE: Number of colors (tones) was: Re: Dynamic range

Hi Preston,

> Bit depth: It isn't so important how many bits a scanner records, but
> rather how good those bits are.

That is, of course, true.

> I suspect most consumer (i.e. under
> $10,000) scanners have difficulty "seeing" 8 bits deep. They can't
> reliably discern the difference in a 253 and 254 shadow value (or is
> that a 2 and 3 shadow value? I never can remember.). Whether they report
> the value as 253.34 or 253.35 is immaterial.

As I said in my other post, the only time the full density range of the
scanner is used, is when it's scanning positives, since they have a higher
density range than B&W negative film...and therefore, you'll only get a few
thousand (if that) differentiated tones somewhere in the 16k (for 14 bits)
range of the CCD.

It's the noise in the system, that will determine the appropriate A/D
converter, which determines how many bits you will have.  I can easily say,
that the current crop of 14 bit scanners can get 14 bits of "pretty good"
data, at least 13 bits...



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