I recently got a K-5, my first Pentax DSLR, though not my first Pentax camera. (I own a K1000 and two MX bodies.)
I have read and understood
the post by Adam on shooting K and M lenses (without the A capability) using the Green Button and so on. Works great!
So I finally got around to trying out a cheap old used manual focus Vivitar 28mm lens that I own (that works fine with my old film bodies). But the Green Button does not make the body meter; and the DOF Preview function (on the on/off switch) doesn't make the lens stop down. The settings on the top display blinks. Worried, I went and tried my various other lenses (with and without A capability) and everything is OK. Just this 28mm lens doesn't work.
The only thing I can figure out that makes it different from all my other manual focus lenses is that it has a plastic mount. Is the K-5 using the metal mounts of even non-A capable lenses to tell if there's a lens mounted? Maybe the camera thinks there's just a plastic body cap on, so it won't meter. (Though it will shoot wide-open only.)
If so, has anyone gotten past this? Maybe a bit of aluminum tape strategically placed on the lens's mount?
I mean, I can l can live without ever using this lens with the K-5, if I have to. It's not a great lens, so no terrible loss really. But I was surprised to see this happen. Any thoughts?