Early I-10, sharp or not?

[ZorkiKat]

Hello Comrade Jay,

Many thanks for this detailed explanation. So I understand that most I-10s are not good for later Russian rangefinder cameras that has a 28.8mm registration distance. Am I right? Kind Regards

Zhang

Comrade Zhang

It's not only the back focal register different with prewar and many early postwar I-10 which prevent them from being used with later cameras or any other LTM camera which conformed to the Leica standard. There is the well-known difference in thread mount pitch which would cause mounting problems or even damage when one type is fitted on the other.

The prewar I-10 and many of the early postwar editions used a different RF coupling cam movement. I've observed that these I-10 have what look to be a shorter camming. A camera whose RF had been adjusted for these lenses will not couple properly with a later lens with 'standard' camming. The first thing which can be observed is that the RF will not line up at infinity with a 'newer' lens. Second, the distance marks will be off in the entire range. The cam depth of these early lenses seem to be shorter than the Leica standard.

Jay

 

[ZorkiKat]

How do you cope with the pressure plate? I always foun d it very difficult to measure depth without either not quite touching the plate or touching the plate and depressing it slightly?

Michael

Michael

You can have a piece of film over the pressure plate when measuring the flange to focal depth. The film will lie where the focal should be, and it's not as easy to depress anymore since the space has become tighter with the film+plate sandwich. Plus, the measuring tool used also matters. I've found that some of the finer calipers have probes which slide down gently and won't bear on the plate. I use a Mitutoyo vernier caliper whose probe behaves this way. On the other hand, my other caliper, a cheaper Dial caliper cannot be used for making focal depth measurements since its heavy probe bears on the pressure plate too much.

Jay