Archived posting to the Leica Users Group, 1997/12/17

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Subject: Re: [Leica] WA infinity performance
From: Alfred Breull <puma@hannover.sgh-net.de>
Date: Wed, 17 Dec 1997 09:19:56 +0100

At 22:46 16.12.1997 +0100, Erwin Puts wrote:
>All lenses are corrected for infinity (the exception of course are the real
>Macro lenses).

Though I hear that statement every now and then also, the correction 
of super wide angles for a hardly used distance sounds a little 
questionable to me. Additionally, there has been an article in the 
German journal "Foto-Magazin" in the 70th stating, that stronger 
wide angle lenses are corrected for closer distances than infinity. 
They spoke specially about both, the 4/21 M and the 3.4/ 21 M Super 
Angulons. Unfortunately I don't have the correct source anymore -
it never came to my mind that I would need to cite the text 20, 25
years later.

>The factory however tested both lenses and found no
>significant deviation from their norm.

That's certainly true, but a dubious argument. How would you feel, 
if you have caries, and your doctor states that there is no 
deviation from the norm - hence he doesn't need to do anything ?
The cited Leitz statement just says something about these special 
standards, but not about the actual infinity performance of the lens.

Alf