Jupiter 12- can we find out which were the smaller ones (to use in non-Zorki/Feds)

[MikeLeFevre]

I want to see if we can identify the smaller rear lens element Jupiter 12's. To try and get a definitive measurement or list. They do exist as some people report they can mount their J12 on a non Zorki/Fed body without the rear lens element getting in the way. The problem is the knowledge of which ones is not known.
A couple of years ago one of the Russian sellers on ebay told me that LTM Jupiter 12's built between the years of x and y had a slightly smaller rear lens element so that they can fit in non Zorki/Fed cameras. Unfortunately I lost the bit of paper I wrote it on, and can't remember the seller now.
It's probably a bit simplistic to think that it will be all J12's between certain years too, more likely ones produced by certain factories at specific times.
So the idea of this thread is to try and find the answer. I'll also post it on the Beststuff Russian camera forum.

Info required:
1. My idea is that everyone with a LTM J12 measures it's rear element somehow, especially the people with the ones we're looking for. How to measure- maybe just a piece of string around the rear lens element diameter? Then you can just lay it out next to a ruler and read off the diameter. Metric measurements in millimeters would be good as then we don't have to deal with that outdated 57/256ths of an inch etc...
2. Also the serial number of the lens
3. The factory that made the lens which you can find out here from looking at the logo on the lens:

http://cameras.alfredklomp.com/logos/

4. Is it one of the smaller ones in your opinion i.e. does it fit okay on a Bessa/Canon etc...?

I think once we establish what the baseline is, that only people with the smaller than baseline ones should post as these are the 'mysterious' ones.
Any other ideas?
M.

[Laika]

Lens - J12 Black (LTM)
S/N - 7602XXX
Factory - LZOS
Dia - 28.9mm (rear glass element)

Lens - J12 Chrome (LTM)
S/N - 6307XXX
Factory - LZOS
Dia - 28.9mm (rear glass element)

[MikeLeFevre]

I'm no good at multi-tasking (the TV was on too loud when I did this post and my girlfriend was talking to me)- someone on the Beststuff forum pointed out that circumference is the measure around a circle not diameter. So I think that was what I was looking for.
A post there has said that their J12 'fits' with less than a millimeter to spare on 1 non Fed/Zorki camera so the elusive smaller element ones may just be normal ones squeezing in, as I was hoping there might be a significant difference. But more postings by J12 users would be much appreciated.
M.

[xayraa33]

Lens J12 bare aluminium ( so called chrome ) ser, no.5300*** {1953] rear element is 28.9mm in dia. Another J 12 ( bare aluminium) from 1960 is also 28.9mm in size. If the J 12 is detrimental to your CV Bessas Health ( or Canon), enjoy it on a Fed or Zorki ,if the Leica or an expensive copy is not an option...... A very nice lens indeed.

[xayraa33]

Use Pi to get circumfrence (3.141 x dia.)

[xayraa33]

I seen some Kiev mount J 12s with the top and bottom sides of the rear element squared off. Would this style of lens in Ltm be usefull to your application?

[FrankS]

black J12 sn.N9009xxx 28.9mm dia. rear element

[MikeLeFevre]

There haven't been too many posts here or on Beststuff, but I coming round to thinking it may just be a case of the odd normal one squeezing in through there being a slight natural manufacturing variance (of under a mm) in the depth of the rear element. One of the posters on Beststuff reported it was dependent on a difference of ~0.7mm in the depth of the rear element between 2 he had, on whether it fitted to a Bessa R he had or not.
~0.7mm sounds like a natural variance in Soviet manufacturing standards to me. So the list idea may be unobtainable, unless someone can come up with an example with a significantly smaller rear lens element.
So it seems like it may be the depth of the rear element that is important not the diameter (or circumference) like I originally thought. The only problem with this is that it's pretty hard to measure differences so small unless you have the right gear.
M.

[Spyderman]

I seen some Kiev mount J 12s with the top and bottom sides of the rear element squared off. Would this style of lens in Ltm be usefull to your application?

I guess that is exactly the thing we (owners of Bessa R) are looking for.

I have a Bessa R and a Jupiter 12. The Jupiter can be mounted on the Bessa, but stops when the rear element touches some light baffle behind the meter cell. At that moment the lens is focussed at about 4m. If the top and bottom were squared off, then the rear element might go deeper into the body, and either work correctly, or touch the curtain and possibly damage it.

[oscroft]

I don't have a micrometer so I can't measure to the nearest 0.1mm, but to the nearest millimetre my two (8705... and 7704...) both measure 29mm.

[OldNick]

I have a black 1987 J 12 which works fine on a Leica IIIf. I don't like to touch the rear element, so I won't attempt the measurement, since everyone seems to get the same number. Great lens!

Jim N.