When I first started using the Carl Zeiss Jena Tessar 50/3.5, I noticed that it could not focus further than about 1 meter. I even thought that my way of adapting M40x1/44 lenses was wrong.
But then I compared the appearance of my copy and other copies (found on the Internet). And the optical unit of my lens is moved forward even when focusing to infinity.
Obviously, the lens was assembled incorrectly, so I partially disassembled the lens to fix it.
First I found the right start of the multi-start thread of the helicoid. This made it possible to focus to infinity, but also to focus beyond infinity.
Second, I found the right number of turns of the single-start thread of the helicoid. This allowed the lens to focus properly.
The lens after these corrections:
The part with the focus limiters:
Looks like someone removed the close focus limiter. Now the lens can focus much closer than 0.6-0.7m.
This copy also allows the aperture ring to be turned beyond f/3.5 (without actually changing the aperture).
I found some photos of lenses with the same behavior. I decided to keep it. It doesn't bother me because the aperture ring is pretty stiff to turn.
Now the lens is fully usable.
See also related notes:
- Carl Zeiss Jena Tessar 50/3.5 (M40x1): Uncoated (non-T) version (2024-05-30)
- Praktiflex M40x1 lenses on modern cameras (2023-08-25)
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