Archived posting to the Leica Users Group, 2000/10/30

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Subject: RE: [Leica] Film megabytes and some curious contradictions
From: Austin Franklin <austin@darkroom.com>
Date: Mon, 30 Oct 2000 19:16:04 -0500

Erwin, I don't know if you're aware of this, but you will never just 'line 
up' your digital sensors pixels with your target.  Say you are shooting 
1:1, and you are trying to record a line that is .001".  You would need to 
sample at at least twice that frequency, or .0005" to pick that up, since 
it could fall exactly between two sensors, and not get picked up by either 
one.

So, when you calculate the resolution you need for a digital sensor to 
record information, don't forget to multiply by (at least) 2x the target 
size you want to resolve to.

I also believe line pairs, are exactly that, line pairs.  So, 40lp/mm would 
be 80lines/mm or 2032 lines/inch but in order to pick them up, multiply by 
2, and you get 4064....  Imagine that ;-)