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

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

> > > > 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.
>
> I don't see any mention of amplitude in the statements you backquoted.

Signals have more than frequency as a characteristic/component, and
amplitude is very important as it relates to film scanners.

> > That is not correct.
>
> Eight years of application of the principle provide strong
> evidence for its
> correctness ... considerably stronger than your assertion to the contrary.

I don't know what you've applied to what, but it sounds to me like you've
never designed a film scanner.  Have you?  I have and therefore have first
hand knowledge of what I talk about with respect to this subject.

> > You do not get any guarantee of accurate
> > amplitude reconstruction with 2xf, nor do
> > you know what the waveform was.
>
> You know what the waveform of a periodic signal is.  And with two samples
> per cycle you can reconstruct it entirely.

Well, for film scanning, periodic signals don't really mean much, unless
that's what you want to scan...but they are good for testing and
characterizing a system.  For film scanning, the two most important
characteristics are "position" and amplitude.

> > 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.
>
> I'm not the only one who said it.  It is nearly self-evident.

I don't care if 100 people say what you say, it doesn't negate that what I
said is absolutely correct, and if you'd take the time to do the little
index card experiment I suggested, you'd understand what I have been saying.

> > Some understanding you appear to be missing is
> > that film scanners are NOT "point" samplers.
>
> Either a sample exists, or it doesn't.

The information content of the sample is very important.

> > They sample a physical "area", and get an average
> > "reading" from that area that the sensor "sees"
> > (is in its FOV).
>
> In other words, they take multiple samples.

Er, huh?  Who takes multiple samples of what and for what reason?

Austin

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