Optical unit replaceable between J3 and J8?

[Alberti]

Can I place a 50mm Jupiter 3 head (optical assembly) in a J-8 barrel and the other way around? Does it then keep the correct distance if I take along the shims that were used for the lens to the new barrel?
Can that be done on a Contax mount and on a M39mm barrel?

Sometimes there are only optical blocks for sale. 😎

 

[goamules]

I hardly think that a bigger, faster piece of glass will fit in the smaller F2 barrel.

 

[Alberti]

Of coarse you are right.
The opening is at the diaphragma, and that increases. So the thread would.
While the outside rim 40.5mm is chosen to encompass the both lenses outer glass (and Leica could stay within 39mm ).

 

[Mr_Flibble]

I think Brian Sweeney would be the best person to ask.
He mostly hangs out at Cameraderie.org these days, though.

 

[Alberti]

I think Brian Sweeney would be the best person to ask.
He mostly hangs out at Cameraderie.org these days, though.

Thanks. That Cameraderie.org is an interesting site indeed for those hacking questions.

 

[xayraa33]

Brian in his hacking heyday was known for putting pre-war Zeiss Sonnar 50mm f 1.5 lenses from the Contax RF bayonet mount to J-3 LTM focusing units. I believe he did some pre war f2 Sonnars to J-8 LTM mounts too and did an I-61d/l LTM lens in Nikon RF mount also. He was a lens hacking expert second to none.