On 4 Oct 2005 at 11:59, graywolf wrote: > In comparison you could say Pentax uses a Hemi Motor for focusing. Old, > big, but powerful. And you don't have to have a separate motor for each > lens. Canon does not use those linear motors because they are better, > but because they are cheap (there is almost nothing to them). Such is > the power of advertising. > > My camera has more buzz-words than your camera. Yadda, yadda, yadda....
Except of course that the USM ring motors are high torque direct drive units which are fast, quiet, accurate and don't suffer gear/drive train slop like remote drive systems so are not prone to overshoot if correctly driven. Also inherent in the design is the fact that as soon as the AC drive is withdrawn the system effectively becomes de-coupled allowing the lens to be focussed by hand without the need for additional clutch components. Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
