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Re: filmscanners: Scanner resolution (was: BWP seeks scanner)

Thank you, Stan. I've seen this test, and I understand it, even though it's 
been a "lot" of years and I didn't know what it was called. :-)  So anyway, 
I'm sorta on the same page now. Not that I've seen the tests, but at least I 
know what they show and what they're about.

Best regards--LRA

>From: Stan McQueen <stan@smcqueen.com>
>Reply-To: filmscanners@halftone.co.uk
>To: filmscanners@halftone.co.uk
>Subject: Re: filmscanners: Scanner resolution (was: BWP seeks scanner)
>Date: Fri, 15 Jun 2001 16:33:11 -0600
>At 08:47 PM 6/15/2001 +0000, you wrote:
>>OK, did I miss something significant here, or did the subject just get
>>changed? I'm *assuming* that "a resolution of 75 lp/mm" refers to 75 lines
>>per milimeter--in which case the "/" is redundant. But of course, film has
>>no lines per anything, it just "is".  Measurable, of course, but any
>>"lines" are artificial.
>Someone else has already mentioned that lp = "line pairs".
>Resolution is tested using special targets that contain sets of lines at
>increasing density. The target is photographed (scanned, whatever) and the
>result is evaluated. The set with the highest number of line pairs per
>millimeter in which you can actually see that the lines are separate
>determines your resolution. It is, of course, an artificial measurement, in
>that, as you imply, an actual scene doesn't have "lines". That's why the
>number is often referred to as the "theoretical resolution" of a lens,
>camera, scanner, or whatever is being tested. It does have a relationship
>to actual picture taking; you would expect a lens, say, that has a higher
>theoretical resolution than another lens to actually take sharper
>pictures--and it really does, all other things being equal. Of course, the
>difference may be too small to see with the naked eye if the difference in
>theoretical resolution is too small. That's because the eyeball also has a
>theoretical resolution.
>Photography by Stan McQueen: http://www.smcqueen.com

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