Originally posted by cdurfor At the base of the lens it says O/OM.
I have the same lens in the M42 mount (which includes the A/M-mode switch). I prefer it to the DA 50-200, for instance, at 200mm. IQ's good and f3.5 vs f5.6 when you need it too.
The mount IS interchangeable to some degree and fairly easy to do IF you have a Pentax mount to replace it with. There are three very small screws just above the aperture ring that allow you to remove the camera-specific mount. I haven't explored this particular lens to determine whether there would be issues with M42 vs P/K vs OM swaps but if you're satisfied with only K/M-mount functioning something could likely be done. OTOH, these aren't expensive lenses and I wouldn't pay to have it done.
Or, make lemonade. Consider mixing an OM and PK extension ring combination to make an adapter ring for a 200mm close-up/macro kit. This doesn't have to be complicated -- just file or sand two smooth mating surfaces and use epoxy glue! Typical FOV results with the associated lose of ~ 1 to 1.5 effective f-stop:
Normal FL = 4 x 6 inch FOV @ ~6 ft
15mm ring = 3 x 4.5 inch FOV @ ~ 4.5 ft
30mm ring = 2 x 3 inch FOV @ ~3 ft
H2