thanks anthony. you wrote what i was going to. the ZD 35 Macro and ZD 25 focus quickly but with nowhere near the speed and silence of the Olympus pro-class lenses I have (ZD 11-22/2.8-3.5, ZD 50-200/2.8-3.5) or Panasonic/Leica lenses (Vario- Elmarit-D 14-50/2.8-3.5, Summilux-D 25/1.4). Obviously better quality focusing motors in those four. The newer generation pro lenses with SWD focus drives are much faster and quieter still.
of course I haven't seen a Panny G1 body yet (and the optional adapter) to test the two 25s on it. i expect they'll work pretty well however. G On Sep 14, 2008, at 3:13 AM, Anthony Farr wrote: > Screwdriver AF doesn't require a lens to be compatible with any > particular > mode of AF control. Hell, it doesn't even need any embedded > electronics > associated with focusing, save for distance reporting not critical > to focus > operation. These lenses can just be dumb mechanisms following the > camera > body's instructions. Compatibility is no issue at all. > > Focus by wire is entirely a different kettle of fish. The lens is an > integral part of the 'brain' of the system, and who other than the > designers > knows what requirements need to be fulfilled. But I can offer this > observation. My old EVF style camera has CDAF focusing. When it > focuses, > the gross movements happen at a fast motor speed, but when it > approaches > correct focus the motor slows considerably for the last fine focusing. > Clearly, this focusing motor has variable speeds. My DSLR is the > "bottom > feeder" model from Olympus, the E-410 which has only PDAF (CDAF not > being > added until the 420 mode, AF during live view is achieved by a > quick mirror > flip into reflex view, and back into live view all in about a > second). Even > considering the humble status of this camera, the AF flies like shit > off a > shovel. It will snap into focus in a trice with no hunting. But my > observation is that the motors in the two consumer zooms I have run > only at > a single high speed. I'm guessing that CDAF needs AF motors that > slow down > as they approach correct focus, and that the cheaper lenses weren't > enabled > for this mode in their original firmware versions. Someone with the > better > 4/3 lenses might comment on their operation. > > IMO this thread is a storm in a teacup, because Olympus has issued > firmware > updates to enable CDAF in live view with the "incompatible" lenses. > > Problem solved. > > Regards, Anthony Farr -- 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.
