> > From: Toralf Lund <[EMAIL PROTECTED]> > Date: 2008/01/28 Mon PM 08:42:00 GMT > To: Pentax-Discuss Mail List <[email protected]> > Subject: Re: k10d vs nikon d80 handling > > Adam Maas wrote: > > On 1/28/08, Brendan MacRae <[EMAIL PROTECTED]> wrote: > > > >> --- Toralf Lund <[EMAIL PROTECTED]> wrote: > >> > [ ... ] > >>> He was talking about hunting. Surely the motor does > >>> not affect that? > >>> > >> Ah, you're right, he was. My bad! Yeah, that's a > >> function of the AF sensors themselves. > >> > >> -Brendan > >> > >> > > > > Not always. SDM lenses hunt a lot less because they won't overshoot > > the mark, they are in effect stepper motors, and are told how far to > > turn the lens, screwdriver AF tends to overshoot more. > > > It should also be possible to hit dead-on every time with an > encoder-based setup like the one of the screwdriver, but I suppose that > may be the case. I'm not sure this overshot may be described as > "hunting", though. It should at least be possible to correct with just > one extra movement in all cases.
Where there is a mechanical focusing linkage joining body and lens on a separable system there has to be some free play, otherwise it would be problematical to get the system to connect when lenses were changed. Free play = focusing error - even with perfect electronics. The trick is reducing the free play enough that the system connects every time but does not have to search for focus too much. The other way around it, which seems to be the way employed in lower end Canons, is "close is good enough". My fathers 350D rarely has a picture in what I would call correct focus. But it gets there much faster than the DL2. ----------------------------------------- Email sent from www.virginmedia.com/email Virus-checked using McAfee(R) Software and scanned for spam -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
