Biometar 120 2.8 infinity problem

[Srdjan]

I have 2 copies of black zebra Biometar 120 2.8 that they couldn't rich infinity. Is their common problems with this lenses. Can someone confirm me how have same lens?

[Attila]

It was opened and assembled wrongly, I had same experience when I did clean a Biometar 80mm f2.8 myself, I lost infinity, I had to give to an expert to adjust infinity

[Srdjan]

I m a expert
Story goes like this
For long time I m trying to find Biometar 120 2.8, it was my last lens in P6 collection. So finally before 6 mounts I bought one. Unfortunately the last glass was in fungi, I tried to clean but I just destroyed it (it was deep fungi). So finally before two weeks i got 120 again in some bigger collection of lenses. The lens was stuck and wrongly assembled.
So yesterday finally I decided to open it, clean the glasses, clean the blades and re-lube it. The parts was not in please.
Because I didn't knew the right position of zoom ring I decided to go as fader as can to camera (infinity direction), a then find the right position. But then surprise!!! in that position (closes to camera) lens doesn't reach infinity. I tried everything dissemble again and assemble, back and forth at least 20 times. There is no solution (without modifying some parts of lens). Ok so I just decided to to replace beck group of glasses with other lens I have. I figure it out that that lens have the same problem, I changed and combined in all possible ways, nothing.
I use it on Canon 6D with adapter (that is ok with other P6 lenses). Then i tried on P6 with magnification and realized same thing.
When I open lens to 2.8 and put it on infinity, focus is on about 20m.
Both versions of my lens are the same, zebra ones with black body. So if someone have this version can confirm me that he can focus infinity, and can measure how much barrel that holds front elements glasses is out of the body when infinity is focused.
Thank you

[Srdjan]

I read read that sometimes east Zeiss have problems with quality control. So I was guessing maybe something is wrong with design.
I sad it is not possible to fix without modification. In one point trying to fix the lens I figure it out that screw-limiter (the one that not allows to move rings more that infinity) blocks whole barrel to go more close to the camera. So maybe this is design problem, maybe fabric change design of lens and forgot to change the size of this screw.

[themoleman342]

There should be no problem with the design. I've never read about the issue before so my guess is it's wrongly assembled. Screw the finely threaded portion in all the way until it won't go any more (doesn't matter the thread, it always ends up in the same place). Then try to screw in the other part. The slots for the guides should stop VERY shortly before where the guides would be. Undo the finely threaded part until it lines up then put in the guides. That's should be the farthest back point. If it doesn't reach infinity after that, then there's a mechanical problem.

[Srdjan]

Yes I tried that, and still I can't reach infinity. That way i was asking about help, if I get time I will post some photos. I m very confused because it's case with two lens. But it also very interesting that I see that firs front barrel is not same length (less then mm but still)...