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[filmscanners] RE: Film resolution - was: Re: 3 year wait



Anthony,

> > But, one thing that is VERY important is
> > there is a difference between sampling sine
> > waves and square waves.
>
> Not from the standpoint of the Nyquist theorem, which applies to any
> periodic signal of any shape.

Nyquist has nothing to do with amplitude, it is only a detection of
frequency of a signal.

> > Though at Nyquist, you guarantee detecting
> > the frequency, you do not guarantee full
> > amplitude.
>
> You can reconstruct any periodic signal by sampling it at twice the
> frequency of the highest-frequency component of that signal.

That is not correct.  Partial reconstruction, only frequency, yes, but not
complete by any means.  You do not get any guarantee of accurate amplitude
reconstruction with 2xf, nor do you know what the waveform was.

> > To sample square waves, and GUARANTEE getting
> > at least ONE "sensor" that contains full amplitude,
> > you MUST sample at 4x f ...
>
> No, to sample square waves and reproduce them with complete accuracy, your
> sampling frequency must be infinite, as true square waves contain
> components
> of infinitely high frequency.

What I said was absolutely correct, and what you said here is irrelevant as
it applies to film scanners, and actually has nothing to do with the
accuracy of my statement.

Some understanding you appear to be missing is that film scanners are NOT
"point" samplers.  They sample a physical "area", and get an average
"reading" from that area that the sensor "sees" (is in its FOV).

Austin

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