[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Rollei] OTish: Origins of the Sonnar

- ----- Original Message ----- 
From: "Nick Roberts" <nickbroberts  
To: "RUG" <rollei  
Sent: Tuesday, February 24, 2004 4:05 PM
Subject: [Rollei] OTish: Origins of the Sonnar

> 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
   Bertele developed the essential design for the Sonnar at
Eranamann. He developed the lens from the Cooke Triplet. The
Ernamann versions were called Ernostar and were used on the
Ermanox camera. The name Sonnar was evidently first used on
a camera which much predates the lens. Bertelle's idea was
to use low index glass in place of air spaces to reduce
flare. The f/1.5 Sonnar, for instance, has seven elements
but only six glass air surfaces, the same as a Triplet or
   The f/1.5 Sonnar also has a "Merte" surface in the rear
element which helps to correct off axis spherical
aberration. It must have been a difficult lens to make
because of the number of cemented surfaces and steepness of
some of the curves.

- ---
Richard Knoppow
Los Angeles, CA, USA