Rob Studdert wrote: > If you are all conversant with the Canon USM and Pentax body driven focus > technologies then you'd know quite simply it's not just another way to do what > Pentax does. Frankly there's nothing particularly smart or appealing about > driving lens focus from a motor in the camera body. Their technology is > cumbersome and dated and isn't noteworthy enough to be able to support a > technology label as a marketing tool or otherwise. If Pentax had some fast, > quiet and efficient AF system with a similarly silly name to USM there would be > something to compare.
IMO, both the Pentax and Canon autofocus systems (and presumably Nikon and Minolta) have enough mutual problems that the noise of the Pentax system is a minor issue. Neither system does well when the frame has various objects at varying distances (they frequently focus on the wrong object) and neither system does well when the subject takes up a relatively small portion of the frame. Neither system is precise enough for critical work. Christian's skimmer pictures worked as well as they did because the skimmer loomed large in the frame, there weren't any other elements in the frame to confuse the autofocus system and there was a lot of contrast between the bird and the background. I believe that the Pentax system would have gotten those shots too. I think the Pentax system is fast enough and efficient enough for most applications. It is a bit noisier but that hasn't been a problem for me. I have far more trouble with the issues I mentioned in the first paragraph and Canon doesn't do any better than Pentax in those circumstances. Tom Reese
