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

["Mike Kersenbrock" <michaelk@aracnet.com>]

Stan McQueen wrote:
>
> At 11:10 AM 5/15/2002 -0400, Austin wrote:
> >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.
>
> As I understand the Nyquist Theorem, 2f is the _minimum_ frequency needed
> to reconstruct the waveform. Are you saying that the theorem has been
> disproven, or that technical considerations make it impossible to achieve
> the theoretical results? Or something else?

I agree with you.  I'd also like to know the justification of why
the "frequency" of the black/white bars has anything to do with
the Nyquist rate (which it doesn't in this case).

Mike K.

P.S. - An experiment for those who like to do such things.  Most all
       phone lines that travel any distance are digitized at a 8Khz
       rate (PCM), which by Nyquist gives a 4Khz bandwidth.  It's really
       less than this due to implementation imperfections and because
       it has to travel analog-style perhaps a few miles through wire
       before getting to the CO where it's digitized.  Try send a 2Khz
       square wave (Black and white) over the phone across town and
       see what comes out the other end.  Then send a 2Khz sinusoid.
       One will work pretty well, the other will not. Even though the
       sampling is at "4f".

P.P.S. - To summarize this "argument", one side says Nyquist was an idiot
         and here's some scanning samples to prove it. Others (like me)
         say Nyquist was a genius and of course the samples don't work
         because the sample rate isn't anywhere near Nyquist's rate, let
         alone more than it.  We at least agree on that "it doesn't work",
         only whether Nyquist's math was any good or not.

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