Quote Originally Posted by ntenny View Post
The big question is whether you believe (like Dante Stella) that the Soviet focusing helical dimensions were slightly different from Leica's, or (like Karen Nakamura) that it's just sample variation and a good Soviet lens is dimensioned correctly. It probably does make sense to do some testing of specific lenses with specific bodies in any case.

My own experience with them has been good, but the only Soviet lens I've used much on a Western body is the 50/2.8, where a slight difference wouldn't necessarily be obvious.

You are quite correct that, if one is planning to use a Soviet lens on a non-Soviet LTM body, individual testing is the best route. I tend to accept Dante Stella's argument (I seem to recall among his sources documents detailing the specified dimensions), though the nature of Soviet QC makes it difficult to know anything for sure.

Let's not forget that the OP was also talking, at least initially, about collapsible lenses, and that no specific body (Soviet or non-Soviet) was mentioned. Given that the only Soviet collapsibles are the 50/3.5 I-22 or I-50, any minor focus variation should be a non-issue regardless of the body.