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



- ----- Original Message ----- 
From: "Marc James Small" <msmall  >
To: <rollei  
Sent: Thursday, May 01, 2003 7:01 PM
Subject: 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
> >Zeiss.
> >  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.
>
> Richard
>
> 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.
>
> Marc
>
> msmall    FAX:  +276/343-7315
> Cha robh bàs fir gun ghràs fir!
>
  Thanks. I wasn't sure of the life of German patents but
seem to remember seeing a reference to twenty years
somewhere. Presumably, the life of the US patent is 17 years
from date of issue whatever the life of a foreign patent is.
  Since B&L continued to make Zeiss design lenses for many
years after WW-1 it would be interesting to know what
arrangement, if any, they had about the _names_. B&L
continued to use the Zeiss names on a number of lenses for
decades. Were they not covered under some copyright law or
did the two companies have some sort of agreement.
- ---
Richard Knoppow
Los Angeles, CA, USA
dickburk  

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