Originally posted by hangu I'm curious as to what the lens contacts do on the back of the lens. There are several of them and I'd like to know what function is attributed to each contact. I'd appreciate any help.
If anyone's curious, I've been meaning to convert manual focus lenses to auto focus. I have problems, I know.
Bojidar Diminitrov has the answer, start from here:
K-Mount Evolution, Features and Operation
Six of the contacts (that are there from the A-generation lenses) are like a binary code for the min and max apperture. The 7th contact that came with the autofocus lenses transfer an analog signal that code much more info. It is not hard to change a K mount into an KA mount with the info on min and max apperture. Unfortunately, this is not enough. In the generation shift from the K mount (and the M-generation lenses) to the KA mount (and the A-lenses) Pentax changed the mechanical transfer of apperture from something like logarithmic to linear. So a DSLR (or any camera with the crippled mount) will still be confused when metering (it meters wide open, then try to stop down for the actual shot, but makes the wrong assumtions on how far to move the apperture leveler). Only a few of the late M lenses were made with linear transfer. I hope I got it mostly right.