--- John Chennavasin <[EMAIL PROTECTED]> wrote: > If a lens is available in both USM and non-USM > versions, keep in mind > that the USM motor is used primarily for marketing
Are you trying to start a religious war ? :-) More seriously though, I have had non-USM and USM lenses. I see USM as much faster and incredibly silent and tack on. Maybe it is only my impression.... > purposes. You > won't get full-time manual focus with any lens that > lacks a distance > scale. USM comes in multiple flavors - hence it behooves to do one's research well. "Ring" type is what I would want. Micromotor USM or AFD lenses may not neccessarily offer FTM (Full Time Manual). I have the 28-135 USM and the 70-200F4L USM - both have excellent FTM capabilities. Perhaps Canon always equips it's Ring USM lenses with Scales - hence your impression. In my view the Ring Type USM is Fast, very silent and tack on - depending on the lens max aperture and ambient lighting and of course, in camera AF capabilities/algorithms. Look here for Phillip Greenspun's article explaining the different characteristics: http://www.photo.net/equipment/canon/lens-motors - Harman __________________________________________ Yahoo! DSL Something to write home about. Just $16.99/mo. or less. dsl.yahoo.com * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
