Sorry a Leica thread mount (LTM) J12 is not compatible with lots of LTM bodies, it can foul shutter blades of Bessas (or Bessa clones) and the anti flare boxes on late Canon VI and P bodies, and the meter arms of CL and M5 bodies. It wont allow TTL meters to work normally even when it will physcially fit as well.
You can only use J12 on some bodies Leca LTM, FSU LTM etc., you only options are get a compatible body or return to vendor or sell on to a 3rd party.
You can damage both the lens and body if you ignore the problem.
P.S. you can use a j12 on an M with a normal adapter, but you should not try this on a M5 or CL. However if you have the adapter machined it is safe on a M5 but not on a CL.
Last edited by Xmas; 01-20-2013 at 08:54 AM. Click to view previous post history.