50mm Elmar construction

[Neil Purling]

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Are there any diagrams of the internal arrangement in the 50mm f 3.5 LTM Elmar ?

Is the optical design unique, or similar to a Tessar? What differences apart from the location of the iris diaphragm between the Elmar 50mm f3.5 and a FSU Industar, which is a Tessar type?

[brianv]

The block diagram of the optics as illustrated by Neblette's "Photographic Lenses", 1965 edition groups it with the Tessar. 4 elements in three groups, 1-1-2 arrangement (front to back). But- that is the configuration of the optics. The "Prescription" of the lens is the term that an optical engineer uses to take into account selection of glass, spacing of the elements/groups, and exact curvature of the elements. That makes a big difference in the performance and character of a lens, even if they are the same "formula".

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[luigi bertolotti]

When speaking of the Elmar 4 elem. design, it has to be considered that it was born as a variant of the original Leitz Anastigmat (the first lens mounted on the Leica 1... dream of collectors), then renamed Elmax : this was an original Leitz design (Max Berek) with FIVE elements, the last being a triplet; then, the last group was redesigned, stretched to two elements, and entered THE ELMAR ... the final 4 elements design (1926), albeit conceived as a variant of the original five-elem. resulted anyway very similar to the well known Zeiss Tessar (which was, by its part, used in other gear made at Leitz factory at that times) and Leitz waited for 1927 (expiry of the Tessar design patent) to apply a patent for the Elmar.

Btw, the Zeiss Tessar was also designed on the basis of a previous design - the Unar - but this came from the same firm.

[Neil Purling]

I have not got a diagram of a proper 50mm Elmar. Can someone scan and post a diagram of the elements in a 50mm Elmar? Is the Elmar 50mm the same (excepting the diaphragm position) as a Tessar if they had to wait for the Zeiss Tessar patent to expire?

It must have been pretty close.

[luigi bertolotti]

I have not got a diagram of a proper 50mm Elmar. Can someone scan and post a diagram of the elements in a 50mm Elmar? Is the Elmar 50mm the same (excepting the diaphragm position) as a Tessar if they had to wait for the Zeiss Tessar patent to expire?

It must have been pretty close.

 

Not an excellent quality...but here are the Elmar 50 3,5

 

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and the Tessar 50 3,5 (the version for Contax - contemporary of Leica... surely there were others "Tessar 50", like the well known "Kino-Tessar"... I think the design was basically the same, maybe different glass formulas)

 

[earleygallery]

BTW the later Red Scale Elmar differed slightly in design as I understand.

[wizard]

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BTW the later Red Scale Elmar differed slightly in design as I understand.

 

True, but the basic design remained a "Tessar"-type. If I remember correctly, the Elmar patent was directed to the different location of the iris.

 

Andy

[Neil Purling]

It does appear like a Zeiss Tessar at first. There are differences in the shapes of the surfaces of the two seperate elements. The cemented pair at the rear of the Elmar looks pretty much the same as the Tessar. To me it looks like the rear part of the cemented pair is somewhat thicker, but this may be due to a slightly inaccurate drawing.

So the Elmar is a re-design of a Tessar so it couldn't be patented, but Zeiss couldn't accuse them of infringment of their patent if the Elmar did vary in the ways the diagrams suggest.

Does the position of the iris have any influence on the performance of the lens?

Do these optics trade max contrast level for a better balance between center & corner performance?

[luigi bertolotti]

I think the question of patents could be more subtle... german-style... Leitz and Zeiss were indeed competitors, but they also had good business relations... Leitz bought the crude glass from Schott, a Zeiss Group company... I even guess they waited for the expiration of Tessar patents after some plain discussion with Zeiss. And, about the "patents story", all the RF coupling system of Leitz was heavily covered by several patents... a reason for Zeiss made a completely different RF coupling system for their Contax.

[giordano]

Does the position of the iris have any influence on the performance of the lens?

 

It helps minimise flare because more of the air-glass surfaces are (loosely speaking) "shaded" from non-image-forming light by the diaphragm (except of course at full aperture). This is trivial today but was significant before lens coatings were introduced.

 

Do these optics trade max contrast level for a better balance between center & corner performance?

 

I suspect the reverse: using more elements would give the designer more control of corrections but (before coating) at the sacrifice of some contrast.

[Neil Purling]

I have just won one on ebay offered by a bona fide camera dealer so I will have the chance to find out about it's performance. Now I am going after a ABLOO lens shade.

[David Hughes]

Just recently I've been scanning a copy of "The Interchangeable Leica Lenses" of October '37 and have put some of them on smugmug. This (David Hughes : photos : Leica Lenses- powered by SmugMug) will bring up what's there so far and "Lenses 05", 06 and 07 show the Elmar lens in cross section.

 

Not the best of scans, btw, but the book is very brittle and I dare not flatten it in the scanner.

 

Regards, David