Tommy Lee , Dec 08, 2008; 11:56 a.m.
I think the most future proof is the Tamron's manual focus adaptall (latest but just before discontinued) version of the 90mm "f2.8" macro. IMHO, it is just as good as the auto focus version but has better mechanical. You can change the mount (via adapter) to all current 35mm format film/digitals, Nikon, Canon, Pentax/Samsung, Sony, Olympus (via OM), Sigma (via M42) and Leica. Should Contax decided to go back to 35mm, it cover that too.