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Re: [Rollei] Search for highest 5 element Planar -- how about Tessar

At 06:09 PM 4/30/03 -0700, Richard Knoppow wrote:
>very good performance. It was patented in 1902 originally as
>an f/8 lens.
>  Faster versions were rapidly developed at Zeiss by Merte
>and others.
>  Nearly every lens manufacturer has made Tessar type
>lenses. In the USA Bausch & Lomb made them under contract to
>  I don't know the date the Schneider Xenar was first
>produced but it would have been sometime after the Tessar
>patent expired, about 1918. 


The life of a German patent is twenty years.  Thus, the Tessar patent
expired in 1922.  This led to the modification of the original Leitz
"Anastigmat" lens to the Elmax, leading to the long-lived Elmar.  The
relationship between Zeiss and Bausch & Lomb was terminated, of course, by
the First World War, but B&L continued to produce a variety of Tessars,
including their famed Micro Tessars, in recent times.


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