Archived posting to the Leica Users Group, 1998/12/01

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Subject: Re: [Leica] Accuracy of x.72 range finder
From: Nathan Wajsman <>
Date: Tue, 01 Dec 1998 18:22:52 +0100

Hi Peter,

According to the depth-of-field tables in Eastland's Leica M Compendium,
at a distance of 2 meters the depth of field of the 75mm Summilux extends
from 1.97m to 2.03m, that is 6 cm. At 1 meter, the DOF is 1.3cm (from
0.993m to 1.006m).

Some time back, Erwin Puts published a table of maximum apertures at
which the M cameras with the 0.72 rangefinder could be focused. The
numbers for the most common focal lengths are:

21mm: f0.15
28mm: f0.26
35mm: f0.41
50mm: f0.84 (so the Noctilux comes close to the limit)
75mm: f1.88 (so the Summilux slightly exceeds the limit)
90mm: f2.71 (so the Elmarit comes close to the limit, while the Summicron
exceeds it)
135mm: f6.1 (so all current 135mm lenses exceed the limit)

Morale: focus carefully with the longer lenses!


Peter Niessen wrote:

> Dear all,
> in his famous article ,,J'accuse Leica'' Mr. Ross proposes the
> following experiment:
> Place a Leica M 2m apart from an object, focus, move 6mm away and
> check if you can see a difference. He states that the depth of field
> for the 75mm Summilux is 6mm at 2m distance. Is that really true and
> not a typi? Common Literature tells that d.o.f. is 6cm.
> However, I wonder about two things:
> 1. Can you see a difference with an SLR there?
> 2. Are there other errors on the range finder? Is there a formula
> which tells you delta_d = delta_d (distance, aperture, rf_base, ...)?
> Cheers, Peter.
> Peter Nießen
> e-mail

- --
Nathan Wajsman
Overijse, Belgium

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