micromoogman
Well-known
Hi
I have a T-coated Jena Sonnar with heavy cleaning marks on frontlens. My question is if it's possible to use a glass from a Jupiter 8? It's for a Contax II.
I have a T-coated Jena Sonnar with heavy cleaning marks on frontlens. My question is if it's possible to use a glass from a Jupiter 8? It's for a Contax II.
sevo
Fokutorendaburando
The chances are somewhat slim - I've seen 1930's manufacturing documents for a large format Tessar, and it had dozens of recipes combining different variations of each element, so they obviously compensated for product tolerances by matching the elements and shimming accordingly. The Sonnar is even more complex, and presumably less failure tolerant, and Kiev 4 age Jupiters seem to have deviated from the original Jena formula.
Even if you have access to a collimator, have the right shims and start out with a early (Jena glass) Jupiter, you will most likely end up with a somewhat different lens - probably with enough of a different focal length that it will not rangefinder focus accurately any more.
If you already have a dead Jupiter and can collimate, go ahead - reducing from two dead to one odd lens is an improvement. It won't be worth while buying one, or destroying a good one - Kiev 2 era Jupiters are barely any cheaper than their Jena counterpart...
Even if you have access to a collimator, have the right shims and start out with a early (Jena glass) Jupiter, you will most likely end up with a somewhat different lens - probably with enough of a different focal length that it will not rangefinder focus accurately any more.
If you already have a dead Jupiter and can collimate, go ahead - reducing from two dead to one odd lens is an improvement. It won't be worth while buying one, or destroying a good one - Kiev 2 era Jupiters are barely any cheaper than their Jena counterpart...
dexdog
Veteran
Brian Sweeney has done this with a number of lenses; he swapped out the front lens group from my CZJ Sonnar dating from 1945 using the front group from a 1954 J8. Should work just fine. As Sevo noted, collimation may be required.
Dez
Bodger Extraordinaire
There is a very slight difference in the diameter of the front element, as I recall, with the J8 being a tiny bit smaller.
Cheers,
Dez
Cheers,
Dez
micromoogman
Well-known
OK, thanks!
Highway 61
Revisited
The Sonnar front element is serrated into a heavy brass ring, the J-8 front element is free, just held in place by the lens front namering.
Yet the swap is fully possible : first you have to break the Sonnar front element to get a free brass ring (don't breathe the glass debris, wear a mask and do it under tap water so that all the glass powder will go away) and then install the J-8 front element in the Sonnar ring. Then you have to center the new front element by slightly tightnening the brass ring lip from several diametrally facing points using a piece of wood (doing this you progressively reduce the diameter of the brass ring lip) until the element doesn't rattle any longer.
All in all it works perfect - you may end up with a front element which won't be centered to the most perfect accuracy but this is not as critical as for the rear group elements.
I did it once with great success, my collapsible Sonnar performed beautifully after that repair (it was having a very heavily scratched front element too).
Yet the swap is fully possible : first you have to break the Sonnar front element to get a free brass ring (don't breathe the glass debris, wear a mask and do it under tap water so that all the glass powder will go away) and then install the J-8 front element in the Sonnar ring. Then you have to center the new front element by slightly tightnening the brass ring lip from several diametrally facing points using a piece of wood (doing this you progressively reduce the diameter of the brass ring lip) until the element doesn't rattle any longer.
All in all it works perfect - you may end up with a front element which won't be centered to the most perfect accuracy but this is not as critical as for the rear group elements.
I did it once with great success, my collapsible Sonnar performed beautifully after that repair (it was having a very heavily scratched front element too).
micromoogman
Well-known
Sounds encouraging. Thanks. I was about to give up on it after reading this:
http://www.sovietcams.com/index.php?-1090910983
http://www.sovietcams.com/index.php?-1090910983