On Sun, Jan 10, 2010 at 04:24:50PM +0800, Sandy Harris wrote: > I have never used an autofocus system. I find myself comparing lenses > with an SDM motor to ones without. For example, the 17-70 f4 has SDM > but 16-45 does not. 55/1.4 does but 50/1.4 and 70/2.4 do not. > > There are plenty of other differences -- notably price, weight and > focal length -- and I have some idea how to balance those in relation > to my usage and preferences. However, I don't have much idea how > important or useful the SDM motor is, so I am asking here. > > Is this something that should be ignored in making a choice? An > important factor? Somewhere between?
My belief is that the screw-drive AF system is a feature which will eventually disappear from Pentax bodies. I see it as analogous to the dreaded Aperture Simulator; it will start off with some low-end body dropping the feature to shave a little off the cost, but a few years later it will spread throughout the product line. At this point I wouldn't buy anything except SDM lenses, just as in 1995 I decided to only buy A-or-later lenses. Not that there's any imminent danger of screw drive disappearing; Pentax still support A-series lenses for (almost) everything, and I expect that to go away long before Pentax drop any support for later lenses. -- 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.
