Quote Originally Posted by Kym View Post
The 50/1.4 A autofocuses
The Ricoh 50/1.7 may jam on your camera unless you cutaway the lug thing
Personally either of the 1.4's would be my choice

What Kym said is right, Ricoh lenses although they are Pentax K mounts have an extra pin and there are many horror stories on these and other forums that start with "Help my lens is stuck on my camera". It`s OK if you know what you are doing and can remove the offending pin.