Paul Stenquist wrote: > . . . One or two lenses were made as an early attempt at > autofoocus. These had a drive mechanism in the lens and depended on a > motor in the camera. They were designated SMC Pentax AF. This short > lived series was soon replaced with lenses that had a drive motor in > the len. This first series of true Pentax autofocus lenses was > designated SMC Pentax F.
That's exactly backwards. The AF lens, only usable with one specially-adapted body, had the motor in the lens. The later series of F lenses have no drive motor, but rely on the body to focus the lens via a mechanical drive coupling. > . . . Next were the SMC Pentax FA lenses. These were > a refinement on the F series, at least cosmetically if not > functionally. There's a considerable functional enhancement; the FA lenses pass far more information to the camera body via the digital contact pin.
