Archived posting to the Leica Users Group, 1997/12/16

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Subject: Re: [Leica] WA infinity performance
From: Alfred Breull <puma@hannover.sgh-net.de>
Date: Tue, 16 Dec 1997 09:52:30 +0100

Milos:

Usually all lenses are corrected for a certain distance, which agrees
to the distance which is probably used most for a certain focal length.
So, while the 50 mm is corrected for a distance at something between
2 m and 5 m, the correction for wide angles agrees to a more close
distance. It would be unreasonable to correct a 21 mm for i.e. infinity, 
if you need the lens's best properties at - let's say - between 0.9 m 
and 2.5 m. So, I think, that both the 28 mms, that I had, suffered at 
infinity from the correction to close distances. 

Different, the infinity "lack" of the 1.4/35 asph M Summilux should have 
another reason. I remember Erwin Puts mentioning, that the 24 mm (I 
believe it was the 24 mm), he was testing some weeks ago, showed the 
same "behavior". Erwin suggested, that this might be a general property 
of aspheric lenses, but he wanted & needed some more investigations. 

Different to my 2/35 Nikkor, the mentioned Leitz lenses have no floating
elements. 

Alf
- -----------------
At 22:40 15.12.1997 +0100, you wrote:
> One possible explanation for unsharpness at infinity
>might be the lens design itself favorizing close distance performance. I
>don't know, but do these lenses have CRC?