Re: [Rollei] OTish: Origins of the Sonnar

[David Seifert <dseifert >]

Nick,

According to the gospel (_A History of the Photographic Lens_, Rudolf 
Kingslake, 1989)
"A much more profitable way to raise the aperture of the Triplet is to 
insert a positive meniscus element into the front airspace.  It appears 
that the first to suggest this modification was a Chicago optician named 
Charles C. Minor."

The commercial development of this design was the Gundlach Ultrastigmat.

The Ernostar design (predecessor of Sonnar) was developed by Bertele at 
Ernemann beginning in 1919.  By 1923 this design had evolved into the 
famous f/2 Ernostar which was fitted to the famous Ermanox.  In 1926 
Ernemann was folded into Zeiss-Ikon and Bertele went to Zeiss.

Quoting Kingslake "The Ernostar lenses were continued in production under 
their old names for a few years and then dropped.  In 1930 Bertele began 
the development of a series of excellent lenses called the Sonnars, based 
generally upon the second Ernostar type (i.e. each lens had a single 
positive element in front followed by a thick negative meniscus-shaped 
component, with a positive element behind). In the high aperture Sonnars 
the thick negative element consisted of a cemeneted triplet, with 
high-index elements outside and a lower-index element between. In this 
respect the Sonnars resembled the Ultrastigmat except that the narrow space 
between the second and third elements was filled with low-index glass 
instead of air."

As an aside Kingslake comments "It is interesting to note that the name 
Sonnar had been used previously by the Contessa Company for one of their 
folding cameras and for the Tessar-type lens fitted to it.  After Contessa 
became part of Zeiss-Ikon the name Sonnar became Zeiss's property."

Looking at the progression of designs from the basic Ernostar design 
through the famous 50/1.5 Sonnar shows the absolute genius of this young 
man who had done what most would be pleased to accomplish in a lifetime by 
the time he was 32.  The fact that he then went on to create the most 
astounding set of ultawide angle designs in the Biogon shows the true 
extent of his genius.  Truly remarkable.

David


At 12:05 AM 2/25/2004 +0000, you wrote:

>This is probably one for Marc...
>
>As I understand it, the Sonnar design dates from
>Bertele's days at Ernemann both in basic design and
>indeed name. But my understanding has been challenged
>by someone else who states: "The original Sonnar name
>and general type goes back before Bertele. He took the
>existing four element design (the type I mentioned in
>my earlier post), filled one of the front air spaces
>with a low dispersion glass, and changed the single
>rear element into a cemented doublet or triplet.
>Certainly he turned a relatively ordinary small
>aperture design into a world beating wide aperture
>design, but the essential type, as well as the name,
>antedates his involvement". So am I wrong? Is it fair
>to say that "The Sonnar design is generally just a
>lens, typically long focus, with a negative three
>element front component (usually two or more groups)
>and a positive rear component, which nowadays is often
>a doublet, but was originally a singleton"? Or is he
>misquoting Kingslake? Or what?
>
>Nick
>
>
>
>
>
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