Lens to adapter alignment

[minoltist7]

I solved incompatibility between APO-Lanthar 90/3.5 and my R3A without messing with rangefinder alignment.
I added thin shims between adapter ring and lens mount. I cut it from piece of aluminum foil , intended for cooking.
This recipe also may work for some FSU lenses.
So now, my APO-Lanthar focuses precisely on R3A, when I start to focus from 1m . But when I start to move focus ring from infinity in reverse direction, I still get small focus error.
Is it normal for Bessas to have some "freeplay" or clearance in rangefinder coupling?

 

[payasam]

Unusual for a lens and a body from the same manufacturer to have such an incompatibility. Hardly reassuring.

 

[former member]

> between adapter ring and lens mount.

I'm reading that you put the shim between the lens and the LTM to M adapter. That makes the stand-off between the RF cam and the follower-arm of the camera larger. If the LTM adapter was not the proper size, this will fix the problem.

BUT- if the problem is with the shim of the lens, it shifts the problem. Be sure to check infinity focus wide-open, an error might have crept in. The problem is that the 90/3.5 RF cam is "geared" or "reduced" to translate the motion of the 90mm lens to the 51.6mm stabdard that the Bessa expects. What you did will work for part of the range, but probably not all of it. The nice thing is the DOF covers most of the error at infinity.

The problem that creeps in with the direction that you focus- sounds like the adapter shifts a little in the mount, and that knocks the cam alignment off. I wonder if the groove to pick up the lock pin of the camera used to hold a lens in place is just too big.