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RE: filmscanners: Scanner resolution (was: BWP seeks scanner)
> > I think there are two issues here. One is that a 4000 dpi scanner
> > doesn't capture 4000 dpi, and I've yet to get a straight answer on what
> > they actually capture.
>
> You won't get one - it simply isn't calculable and varies empirically
> according to subject contrasts, luminance and colour.
>
That is what MTFs (Modulation Transfer Function) are for. The MTF for
optical systems can be either computed (see Canon's EF Lens Work) or
measured. This can be done taking into account any system variables you
want, such as contrast, luminance, or color. Normally MTFs are used for
systems that are linear-shift invariant, i.e., they have the same response
if you shift the object and if you double the light on the object the image
gets twice as bright. But this is not a requirement, it just makes the
application of MTFs much easier.
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