Archived posting to the Leica Users Group, 1997/11/17

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Subject: Some weird mathematics
From: Erwin Puts <imxputs@knoware.nl>
Date: Mon, 17 Nov 1997 20:29:09 +0100
 
There is a mechanical/optical relationship between the accuracy of the
rangefinder and the baselength in relation to the maximum aperture/.
The equation will be published elsewhere, but here is the result:

Focal length	Max aperture	Max aperture
		M3		M2, M4, M5, M6
21 mm		0.12		0.15
28 mm		0.21		0.26
35 mm		0.33		0.41
50 mm		0.67		0.84
75 mm		1.5		1.88
90 mm		2.17		2.71
135 mm		4.88		6.1

This equation then tells you that the 21 mm can be reliaby focused when the
maximum aperture is f/0.12 (incredible!).
At 50mm the Noctilux approximates the theoretical maximum values when
attached to the M6.
The 135mm seems to be overstretched when used at its maximun aperture of 2,8.
Hope this info has some value
Erwin