Doing a Postscript on this old thread as it was referenced recently. I had twenty-five 50mm lenses in LTM in 2009. I'm somewhere around 75 now. Did about 50 conversions of Sonnars to LTM, kept 5 of them. Skyllaney now offers this service. Have 10 "cherry-picked" Jupiter-3's, three of them are German Wartime Sonnars including Zeiss SN on the rear fixture. Also have a pair of Jupiter-3+, superb.
The rear triplet of the Canon 50/1.5 is often damaged by etching from lubricants used. I was given a Canon 50/1.5 with missing rear triplet for some work done. Opitcally: The rear group of the Canon 50/1.5, Jupiter-3, and Nikkor 5cm F1.4 are very close to each other. Diameter and fixtures: not interchangeable. SO: I wrapped the triplet in copper tape so it would screw into the Canon. I had to do a two-point calibration for position: near and far. That meant getting focus correct at infinity by screwing the triplet into position and setting the main shim correctly. This would be easy on a modern digital, but I used a TTL viewer and a Canon III rangefinder. I did this out of curiosity, wanted to see how far the Sonnar design can be pushed. It worked. Originally, I used a J-3 triplet. I later replaced the J-3 triplet with a Nikkor 5cm F1.4 triplet that I got on Ebay. After getting the rear triplet into the correct position, used epoxy to secure. Not pretty, but works. I'm doing an article on Sonnars, will include some shots with this one of a kind lens.
