Also including the Zuiko 35-70mm f3.5-4.5 PF, and 50mm f2.0 PF lenses. After a mediocre attempt at SLR autofocus with the OM-707, Olympus came up with the idea of Power Focus. This was focussing by a knurled ring at the back of the camera instead of a ring surrounding the lens. It was probably a case of too little, too late, as AF had taken off in the consumer market.