Biotar 58/2 (Praktina) with fixed macro extension, how to remove?

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ant!

Member
Joined
Dec 13, 2017
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422
Location
Montreal
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Hi, I bought an ok priced Zeiss Jena Biotar 58/2 for my Praktina. Weirdly, it has a fixed macro extension attached. I have as well a kit of the auto-extension rings described in http://www.praktina.com/puacc05.htm , but it's not like these which are removed like a standard lens. But looking closer, it actually might be a manual extension ring in the same link, type 1a + b.

The seller described it correctly, mentioning the extension ring and that he had seen it before on another lens, and never tried to remove it since he had the same lens without it. But with the ring, infinity is at maybe 30cm, and I prefer it for normal use, so want to remove it now, but can't figure it out. Further, due to the manual extension ring, the semi-auto aperture doesn't work.

I can unscrew the actual mount, which seems to be the ring 1a according to the link above. The next ring (probably 1b) is stuck, I can't figure out how to remove it. It has a tiny screw on the side, but removing it doesn't loosen anything. I guess it could be the ring is seized due to the age? Usually Praktina mount lenses need the breech-lock ring of the camera to turn, so I assume the ring which is stuck is also a breech-lock ring, but doesn't move. Besides force, anything I can use to carefully remove it, without damaging anything (actually, damaging the macro ring would not be a problem...).

Here how it came:
20230711_213742.jpg


Normally, a Praktina mount would look like this: Praktina mount.

Here the side with the screw, removing it doesn't do anything:
20230711_213759.jpg


And here with ring 1a removed, but the other ring still stuck:
20230711_214115.jpg
 
OP
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ant!

Member
Joined
Dec 13, 2017
Messages
422
Location
Montreal
Format
Multi Format
Any ideas how to get this off? Looking at my auto-extension rings, the small screw probably does not need to come off.
For now I just tried turning it by hand, with some rubberbands over the ring and lens to prevent slipping.

What would be next steps? Somehow a larger wrench, I am afraid of damaging something? I guess oil is also not a good idea, any thing else which I could apply to get it loose but doesn't attack glass, coating or metal? Or grinding the ring off, we have at work a dremel tool...

I guess this is in the end not different then removing a stuck filter, just on the other side...
 
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