"Experimental" 1933 Carl Zeiss Jena LTM 5cm F1.5 Sonnar

Sonnar Brian

Sonnar Brian

Product of the Fifties
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This lens is on loan to me to test out. I believe it was done as an experiment by Zeiss to test the feasibility of using their lenses on the Leica. The SN of this lens is from the 144 block, years before the 272 block of production LTM lenses.

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I doubt this particular design was ever considered for actual production in it's present form: the exposed helical would be a problem.

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AND- the focal length is the Zeiss standard. The lens appears optimized for close-up and wide-open work, but actual focus falls short of infinity. Stopping down to F4 results in the actual focus shifting backwards- and increased DOF making the results acceptable for infinity work. Bottom-line, 15m at F1.5 is good, beyond that- stop down.

100% crop, treetop at F1.5.

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100% crop, at F4:
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the full-frame, F4

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Other than its historical significance, Brian, does this lens have any special features that set it apart from later CZJ lenses? Is it the focus shidt?
 
raid said:
Other than its historical significance, Brian, does this lens have any special features that set it apart from later CZJ lenses? Is it the focus shidt?
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My opinion: the optics are the standard used for the Contax mount, and it was made into this Leica test mount instead.
 
Looking at these images, compared to the Leitz Xenon and even the coated Summarit that replaced it...

Zeiss could have sold a lot of these lenses. They needed to move the rear module in slightly to reduce the focal length. And use a realistic focus mount, as they did beginning with the 272 block of lenses that followed ~7 years later.
 
Brian, thanks for posting these test images. That Sonnar is a beauty used close up and wide open; impressive for a 70+ year old lens. The resolution is quite good, and wonderful color rendering too (as far as one can tell with a digital image posted on the web). Also good to hear that it can be used at infinity, if stopped down to f4 or so.
 
I approach old lenses more as an Engineer. If an RF coupled lens agrees with the RF when used close-up, but not at infinity- the focal length is different from what the RF is calibrated for. That simple. Either change the focal length, or shim the lens for the desired sweet spot and be aware of the short-comings. I do that for Jupiter-3's and Jupiter-8's, and when converting pre-war Sonnars to Leica mount. So when this lens fell short of infinity when used wide-open, no surprise. The focal length is longer than what the RF is calibrated for.

I stopped following the Zeiss list a while ago.
 
I thought that it would be interesting to compare the 1933 LTM experimental lens with standard Contax mount lenses of the period. The f:2 Sonnar on the left was made one year before the experimental lens, in September 1932; the f:1.5 Sonnar on the right was made 6 months after the experimental lens, in April 1934. Not a lot of similarity in the lens barrels of course, given that Zeiss had to produce a helical in the barrel for the experimental lens. Assigning a small group of skilled designers and craftsmen to produce a mere handful of lenses would have involved a lot of time and considerable expense.
 
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Called "IR&D", Internal Research and Development- and sometimes you just let the engineers and machinists have some fun. I'm guessing the lessons learned from this lens led to the changes made for the wartime LTM Sonnar. It's fairly amazing how a skilled machinists can "knock something out" fairly quickly. I've had some custom fixtures done at work with a local machine shop. I have two wartime Sonnars in LTM, and a couple "post-war" in LTM that are more unique.
 
dexdog said:
I thought that it would be interesting to compare the 1933 LTM experimental lens with standard Contax mount lenses of the period. The f:2 Sonnar on the left was made one year before the experimental lens, in September 1932; the f:1.5 Sonnar on the right was made 6 months after the experimental lens, in April 1934. Not a lot of similarity in the lens barrels of course, given that Zeiss had to produce a helical in the barrel for the experimental lens. Assigning a small group of skilled designers and craftsman to produce a mere handful of lenses would have involved a lot of time and considerable expense.
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My 1.5 Sonnar is three numbers away from the one on the right, interestingly enough.

JT
 
The testing continues. Borrowed this lens today from dexdog (thanks!) & hope to put it through its paces. Not sure what happened to the earlier photos, but I will be posting some example shots ASAP.
 
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