Originally posted by alamo5000 A, M, K, Screw...arrgggg...
Somebody here will provide a link to a reference on lens mounts. Here are the basics:
* 39mm screwmount: could be Leica-compatible LTM, or Zenit-compatible M39, or enlarger-lens L39. M39s can be used on Pentax SLRs but avoid these for now.
* M42 screwmount: most Takumars and many many other lenses. An adapter is required. We'll tell you all about adapter pretty soon now.
* M-mount (also K series, marked only as SMC): only mechanical aperture control. You must be in Manual mode to use these. Cheap and fun.
* A-mount: has contacts on the lens base for electric aperture control. Easy to use and more expensive generally.
* AF-mount: these are F- and FA- and DA-series. The DAs are for dSLRs and will vignette on FF film cams. The others work just fine on dSLRs too.
Again, there's much more. This is a start.