--- Tom Reese <[EMAIL PROTECTED]> wrote: > 1. the real world differences between the older EF > (electronic focus) lenses and the newer EF USM > (electronic focus ultrasonic motor) lenses?
Hi Tom, All current Canon EOS SLR Lenses are EF lenses (Electro Focus). Look here for more info: http://www.canoneos.com USM Lenses are further subdivided into categories. Perhaps this dated but useful article could help: http://www.photo.net/equipment/canon/lens-motors > Is the newer EF USM demonstrably faster with long > telephotos? Fast AF is a function of many factors, inlcuding lens design, whether USM or not, in camera AF capabilities, ambient lighting, max aperture of the lens etc. I do not know if there are versions of USM that are different for longer lenses. > 2. Are the newer IS telephotos optically better than > the earlier non IS telephotos? AFAIK, presence of IS has no bearing on the optical charactersitics of any lens. IS just reduces external vibration so that, a shaking hand, for example is prevented from completely ruining a shot. IS is present on a wide variety of lenses, some with a reputation for optical excellence, some not. Presence of IS grows critical the longer the focal length. I wish my 70-200F4 had IS. Even though it is a darn good (optically) lens, even minute vibrations are amplified easily at the long end and tend to ruin handheld shots, esp. in low light with slower shutter speeds. In the absence of IS, use of the following may mitigate the bad effects of vibrations: a tripod or a bean bag or even mirror lock up (for absolute peace of mind) on a tripod ! HTH, - 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 ***********************************************************
