Re: The meaning of letters in lens names?

[Paul Stenquist]

Thanks John for straightening this out. Of course you're correct. The 
AF enses incorporated a bulky motor. It's a complicated history that's 
difficult to present accurately.
On Sep 1, 2004, at 11:08 PM, John Francis wrote:

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.