Originally posted by Cuthbert I never shimmed any of my SU lenses and they all work fine with all my cameras...am I lucky?
Perhaps! The matter has been tossed around the rangefinder forum at length for a number of years and there are multiple articles on the Web regarding such by many reputable people. Here is the summary:
- The issue is with FSU LTM lenses on non-FSU bodies. FSU lenses on FSU bodies work fine.
- The full explanation is quite long and is related to the Zeiss vs. Leica standards
- Apparently the coupling cam on the lens extends at a different rate on the FSU lenses. The result is backfocus at moderate to close distance when these lenses are mounted to German or Japanese LTM or M-mount cameras.
- The problem is more severe with normal and longer lenses
- Whether this is true for all FSU LTM lenses is not clear, particularly in regards to those originally sold with the Drug camera
- The standard solution (pioneered by Brian Sweeney) is to shim the mechanism for the lens rangefinder cam. The details are published various places on the Web.
The difference is readily apparent when comparing the distance scales for the same lens and subject on different cameras. The gold standard (of course) is actual images on film or ground-glass at the film gate. I have a junk SLR body and am planning on scavenging the split-image focus screen from that camera to test my FSU lenses on my Canon P.
Steve