Archived posting to the Leica Users Group, 1998/05/05

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Subject: Re: [Leica] 6.8 Telyts
From: "Henning J. Wulff" <>
Date: Tue, 5 May 1998 19:44:52 -0700

>> The 400/6.8 on a VisoIII was always a real delight for me as far as
>> handling went. I shot birds in flight at 20 feet, which you could't do with
>> anything else (except may a Novoflex) before autofocus. Unfortunately, the
>> field curvature in my lens actually changed with time (and the lens got
>> less sharp), so I got rid of it in the mid 70's.
>Anyone know how this could happen? "field curvature in my lens actually
>changed with time"

The explanation given to me was that some glasses (glass being a fluid) can
indeed flow enough in a normal span of years to cause this. Leica has used
a number of exotic glasses, and I was told that this might have been the
cause. Separation of the two elements had not taken place. One other person
has related the same thing (re: a 400/6.8) to me.

   *            Henning J. Wulff
  /|\      Wulff Photography & Design
 |[ ]|