Archived posting to the Leica Users Group, 2001/07/26

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Subject: Re: [Leica] Nyquist again (was scanning)
From: "Mxsmanic" <mxsmanic@hotmail.com>
Date: Thu, 26 Jul 2001 11:56:23 +0200
References: <NABBLIJOIFAICKBIEPJJAEBAKMAA.darkroom@ix.netcom.com>

Austin writes:

> The problem is "virtually any alignment".

Not really.  Only a handful of very precise alignments will produce artifacts,
and those alignments are extremely improbable in practice.

> Of course I disagree, because your claim is
> wrong.  It would be a range, equal to 53 lp/mm
> down to 1/2 that.

I didn't ask for a range, I asked for a specific figure.  If you are going to
give a range, then I expect to see the MTF curves themselves.

> This is really really simple to understand.

Perhaps, but since there is so much more to resolution, image capture, and
visual perception, it may also be simplistic in consequence.

> 1/2 that and I've explained why.

No.  You've mentioned it, but you haven't explained why.

> You haven't explained why, nor have you
> explained why my correction to your mistaken
> assertion is not correct.

In my previous post, I explained a great deal about why 53 lp/mm, apart from
being quite achievable in the scanner, is also more than adequate for virtually
all purposes.

> Yeah...and isn't 44.1kHz slightly more than
> 22kHz?

Yes ... but you said 20 kHz.

> Reliable is hardly amorphous.

Well, provide some figures that define it, then.

> I have given you a very clear definition of it.

No.  A clear definition is something like "50% modulation transfer at 40 lp/mm."
Something with numbers, that is.

> As I stated, it is a standard term in signal
> processing, and if you have any experience in
> signal processing, as you claim you do, you would
> understand what "reliable" means, and that it
> is a VERY specific term.

I'll understand it when you put numbers behind it, as I have been doing for my
assertions all along.

> You made the original claim, and you still fail
> to substantiate it.

I gave the numbers and sources in my previous post.

In reply to: Message from "Austin Franklin" <darkroom@ix.netcom.com> (RE: [Leica] Nyquist again (was scanning))