Archived posting to the Leica Users Group, 1996/04/04

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Subject: La in Leica glass
From: (Charles E. Dunlap)
Date: Thu, 4 Apr 1996 10:39:34 -0800

So, are the optical elements in all current M lenses made with glass
containing Lanthanum (or other REE)? Is the incorporation of REE now common
among modern lens manufacturers or does Leica still lead in formulating
better glass and/or using it more extensively?

>The first "glass explosion" occurred in the late 1800's when Ernst Abbe
>convinced Otto Schott to dedicate his glass research to the development and
>production of high-refractive index optical glasses.  The second occurs in
>the late 1940's when Leica developed the use of rare-earth glasses,
>especially Lanthanum mixtures.  As Laney wrote in his Leica Collectors Guide
>(p. 123):
>        The decision of Leitz to set up their own glass research
>        laboratory after the war, probably to reduce their dependence
>        on Schott who naturally favoured their parent, Zeiss, was
>        the step that revolutionized Leitz lenses in time for the
>        M3.  Its first major achievement was in making practical,
>        highly refractive glasses with low dispersion by incorporation
>of lanthanum oxide in the melt... The first fruit of this
>        investment was spectacular -- the 50mm f/2 Summicron of 1953,
>        which set entirely new standards for 35mm camera lenses.
>And, later (p. 132):
>        Summicron 50mm f/2:  Clearly derived from the Summitar, but
>        with a superior performance brought about by new glasses giving
>        the designer greater freedom... Three of the elements were made
>        from glass developed by Leitz.
>The prototype Summicron -- the prized "Star Summitar" -- dates from early 1952.
>Other authorities discussing these developments include Keller and Rogliatti.
>Leitz pioneered the use of computers in lens design (1949) and the use of
>rare-earth glasses.  The Wetzlar, and now Solms, insistence on being at the
>cutting edge of technology is quite, quite impressive!
>  FAX:  +540/343-7315
>Cha robh bas fir gun ghras fir!