I third (fourth? fifth?) the motion- I-50 are really mean lenses. No need to get an Elmar if you've got one of these. My 1961 Elmar 2,8's only advantage is its slightly larger aperture. This German lens also feels "cheap".
Your I-50 may need to be adjusted (usually by shimming) to focus right. Jason is right, by the time I-50 and the Zorki in question were made, the "standard" Leica registers had already been adopted by the factories. But then again, that's not always necessarily true.
Many of the Zorki (later ones at that) I got often were not on the 'dot'- having slightly shorter or longer registers than the standard 28,8mm they were supposed to have.
Or someone else, long before you got your camera, may have adjusted its shimming to conform with the lens he had for it (the lens on the camera now may be different, as these could change as they change hands). Adjusting the camera is easier than adjusting the lens, so this is very likely.
Or it could be that the lens was serviced improperly. It's so easy too, to forget to put the right shim in place, or to put all that were needed - after working on the lens.
Jay
