On 12 Feb 2003 at 14:38, gfen wrote: > As for USM? Perhaps I'm missing the point of just what makes USM > special..I was under the impression that the biggest difference was that > there was a motor in each lens to focus, and not a motor in the body with > a screw... While there may be a patent for the Canon way of doing this, I > can't imagine it would be that difficult to come up with the same concept > in another manner and avoid the patent law?
USM has many advantages including; compact and light, shape allows it to be fitted exactly where it is required to limit need for geared coupling, near silent operation, huge torque, easy to control, few moving parts, high reliability and low expense to manufacture. That's all, ie they were a very good idea. Cheers, Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications.html
