I recently received a Jupiter-12 in Contax/Kiev mount. This 35mm f/2.8 lens is a Zeiss Biogon copy, including the extremely prominent protruding rear element. I bought the lens knowing it had a "smudge" on the rear element, but the photo didn't clearly show it as being perfectly centered on the rear surface -- it's a collection of little scratches forming a circle not quite a quarter inch across.
I've filled the scratches with India ink, so far as I'm able, and I don't yet know whether they'll have a significant effect on images (but I suspect they will, due to the size of the affected patch).
As a hedge, I've got a low bid on some spare parts, a lens block from the same model lens, but without the mount and focusing parts; it's just the glass and diaphragm.
Now, the rear element/group unscrews pretty readily on the one I have, leading me to wonder...
Were these lenses manufactured consistently enough to permit swapping the rear groups without changing focal distance or destroying image quality? If so, the spare bits I'm bidding on will fix me right up; the rear elements appear in excellent shape. Otherwise, I'd be stuck trying to swap the entire lens block into the mount and focusing system I have, possibly also having to set the focus to sync with the rangefinder. Is that a hair-raising project, one that will make me wish I'd just spent another $40 for a different Jupiter-12? Or is it reasonably accessible to someone who fixes stuff (including 60,000 rpm pencil grinders and pneumatic scribes the size of a fountain pen) for a living and has cleaned and lubed a number of leaf shutters?
I've filled the scratches with India ink, so far as I'm able, and I don't yet know whether they'll have a significant effect on images (but I suspect they will, due to the size of the affected patch).
As a hedge, I've got a low bid on some spare parts, a lens block from the same model lens, but without the mount and focusing parts; it's just the glass and diaphragm.
Now, the rear element/group unscrews pretty readily on the one I have, leading me to wonder...
Were these lenses manufactured consistently enough to permit swapping the rear groups without changing focal distance or destroying image quality? If so, the spare bits I'm bidding on will fix me right up; the rear elements appear in excellent shape. Otherwise, I'd be stuck trying to swap the entire lens block into the mount and focusing system I have, possibly also having to set the focus to sync with the rangefinder. Is that a hair-raising project, one that will make me wish I'd just spent another $40 for a different Jupiter-12? Or is it reasonably accessible to someone who fixes stuff (including 60,000 rpm pencil grinders and pneumatic scribes the size of a fountain pen) for a living and has cleaned and lubed a number of leaf shutters?
