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[OM] rangefinder resolution

Subject: [OM] rangefinder resolution
From: William Sommerwerck <williams@xxxxxxxxxx>
Date: Thu, 11 Feb 1999 06:22:26 -0800
> Doris Fang wrote:

>> I was reading the other day that an M6 can discern focus to the depth 
>> of one human hair at 3 feet. No SLR, especially AF, can do that.

> yes, but can *you*?

That is exactly the point. You can see the difference with the long-base
rangefinder. Not academic at 1.4...


When this was originally posted, I assumed Doris Fang was joking. To
quote Douglas Adams: "This is, of course, impossible."

A human hair is less than .01" in diameter. Suppose a rangefinder can
focus down to 3'. A resolution of .01" at 3' is better than one part in
a thousand!

Even assuming you could turn the focusing ring such a tiny amount
without backlash, could you actually see a 0.1hift of the double
image in the rangefinder? I really, Really, REALLY doubt it.

A rangefinder would have to have a VERY long effective baselength to
provide .01" resolution. Such resolution isn't needed anyway, because
it's much greater than the minimum depth of field of any lens.

"Think, people, think!" -- Lex Luthor, "Superman -- the Motion Picture"

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