[filmscanners] Re: Density vs Dynamic range

["" <peter@softwell.co.uk>]

> Plain and simple, do you agree that a dynamic range of 5000:1 REQUIRES
> 13
> bits to represent every integer value between 1 and 5000?  If so, then
> where's the problem?  If not, then plain and simple, why not?
>
> Austin
>

I think where we differ is the assumption the a 5000:1 dynamic range
yields 5000 discrete integer values. Light intensity is a linear value so
that 5000:1 range can be divided into as many steps as you'd like to use.
It is in any case only a ratio and therefore has no units or integer
values. 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.

If the CCD has an integrated A to D and thus the number of output bits is
fixed, then I'd agree with your statement.

If not, then your statement is still wrong, or at best, an
over-simplification.

I've followed this discussion with some interest and realise that many
people are confusing number of bits (i.e. the number of discrete values
that can be represented) with the dynamic range of the CCD which could
with the right A to D behind it, provide as many bits as required.

I'm sure you'll agree that it's the noise floor and the saturation level
that define the true dynamic range.

Peter

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