zeiss jena tevidon beyond repair?

skyegreen42 · Joined: 22 May 2024 Posts: 2 Location: usa

check photos for better context. I apologize for the likely improper terminology

l went beyond my abilities and opened my (rare) carl zeiss jena vario-tevidon 15-150mm c mount to spray out dust in between two of the elements just below the aperture section. upon reinstallation, one of the stationary glass elements went into a tube sideways and got stuck. (there will be three times in this order of events which you may call me an idiot. this is the first.)
I got the glass out by bending the metal tube parts so I could relieve enough pressure to pop the glass out, but of course now the threads on the metal tube aqre damaged and I cannot hold the final elemnt in this selection in the tube.
I'm fucked, what next? ive been thinking about either shaving off the mangled parts so the cap which holds the final element in place can catch something. I loved this lens, but I guess not enough to pay someone professionally to clean it for me. ive got no choice now because its become a pretty serious job

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Zamo · Joined: 08 Feb 2019 Posts: 167

visualopsins · Expire: 2025-04-11

Welcome skyegreen42!

screwing into a 1" x32tpi thread-repair die might fix that. (I'm not certain that is correct thread size, but you get the idea, eh? Find the correct size die...)

kiddo · Joined: 29 Jun 2018 Posts: 1185

Probably the best thing it would be to machine a ring as the one damaged and try to insert it into it's place (by threads, so the actual one it would need to be cut and threaded of course it would be a very precise job and not cheap I guess)

skyegreen42 · Joined: 22 May 2024 Posts: 2 Location: usa

I wanted to provide an update to my barbaric toying with a (rarer than I first understood! https://zeissikonveb.de/start/objektive/sonstige_objektive/tevidon.html) cine zoom lens. I bought a second example of the lens with serial number 1530 and was pleased to find that it was in much healthier shape optically than the 1186 I've been working with. It exhibited higher contrast and cleaner performance wide open. It displayed no signs of tampering unlike the 1186, which was a welcome surprise UNTIL I tried using the zoom function.

I discovered that at exactly 80mm, the two lens groups waltzing within the tracks of the zoom barrel would kiss and subsequently shift the elements out of alignment for the duration of the movement (to 150). It would lose its parfocality and in fact not even hit infinity within this range. The seller claimed mechanical wear, but inspecting the barrel gave no clear signs as to what could have changed over time. No signs of a drop and because of the condition of the optics and other movements... aperture blades are spotless and focus is still smooth... and upon further inspection of this zoom barrel versus the other shows that the 1530 seems to have a rougher machined piece as opposed to the 1186. I swapped the groups into the barrel of the 1186 and now the zoom performs smoothly and accurately. Of course I also regreased metal on metal parts and thus the movements feel transparent. It also seems to have improved sharpness and aberration uniformity. But I must live knowing that I have acted as the fun police for the two lens groups as they can't embrace physically anymore.... such a sadness.

Here are two demonstrations of works I've done exclusively with this lens paired to a GH5s.

https://youtu.be/BIav1fvZgbM

https://youtu.be/R3UmQxDInjM

And a photo of her.

____

Now here's some weird observations on these guys.
The front enclosure of the 1186 is painted black and the 1530 is not, instead sporting its natural bronzing (?)
The grand front doublet of the 1186 is thinner than the one on the 1530, but the spacer of the 1186 between it and the element behind it is longer than the one from the 1530. Coating on the 1186 is cooler looking than the 1530.
Some of the doublets/lens groups on the 1530 have far more reflective edges than the ones from the 1186.
The 1530 has none of the screw holes which facilitate installation into the VFA1021 enclosure.
1530 also has finer pitched gears than the 1186, and the zoom ring is completely smooth. (Neither of the units are the 0.8 pitch standard)
The mount holes spanning the entire body of the 1186 are direct points for atmosphere (humidity... moisture... spit....) to contact and hang out on the face of every element as well as all of its mechanics within.
Though everything is marked with matching serial numbers, the 1530 had its uppermost moving zoom element group as well as both rod retaining plates marked as 1450 IIRC. Interesting....
The haze on 1186 I'd previously observed and thought to be just grease turned out to be little pits in the glass? Because this element is relatively free from, like, a sandblaster I am having trouble guessing what's up here. Here's a photograph

Cheers

visualopsins · Expire: 2025-04-11

Nice hand grip too!

Congrats