:It seems the most likely source is a Tamron Adaptall 2 lens that has a
:designation of "OM" on the camera side of the mount.
(..)
:I have heard that there is a possibility that some older Vivitar lenses may
damage
:the button, but I've got some pretty old Vivitar lenses
:(1975 vintage) and can't see any possibility of damaging the button with
them.
Rumours, suspicions... Here are the rules: ALL OM Zuikos, even archeological
excavations like the 55/1.2 and the 28/3.5, have three, evenly spaced screws
in the mount. This setting 100 0uarantees that the spot reset button in the
lens mount of the OM-3/OM4(Ti) is spared.
Now some third-party mounts have more than three screws: 4 or even 5,
sometimes evenly spaced and sometimes not. These are possible
button-smashers. To be sure, just mark the posistion of the button and the
position of the suspicious screw, and watch what happens when you slowly
mount the lens. The button isn't shred off immediately, only by continously
mounting and demounting.
The thing to do when you find a problem screw is to fill the space with
epoxy / two component glue. If you want the lens ever to be serviced, you
better remove the screw before filling the hole. After this little surgery
the mount is 100% reliable.
Problem lenses that I have are both my Adaptall 2 mounts (but the recent
thread showed that there are also good ones, but that their identification
other than the method described above was unclear), my Tokina 500/8 and my
Panagor 100-300/5.6. Fortunately most third-party lenses are ok, so this is
not a reason to avoid them.
Hans
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