Simviation Forum - Difference between a non USM and USM lens??

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Difference between a non USM and USM lens?? (Read 226 times)

Nov 15^th, 2007 at 11:17am

MrJake2002 Offline
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Porthleven, Cornwall, UK

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Hello. I'm looking to buy myself a DSLR camera (probably a Canon EOS 400D Digital Rebel XTi). It comes with the 18-55mm lens kit and you can get a EF90-300mm non USM lens fairly cheaply with it. I was wondering, what is the difference between a non USM lens and a USM one? I've noticed most people have USM lenses but im not sure what it means. Embarrassed

Help appriciated.

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Reply #1 - Nov 15^th, 2007 at 11:23am

Hagar Offline
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My Spitfire Girl
Costa Geriatrica

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USM means Ultrasonic Motor. http://photonotes.org/cgi-bin/entry.pl?id=USM

"USM.

(Canon) Ultrasonic motor. Canon’s name for their ultrasonic lens motor system.

Ultrasonic motors work through the principle of motion induced by very high-frequency vibration. USM lenses are thus very fast-focussing lenses and nearly silent (to human ears, anyway) in operation.

Ring USM lenses (lenses with USM motors in a ring configuration around the barrel) do not use gears and so FTM (full-time manual) focussing is possible. Cheaper micromotor USM lenses, however, use gears and usually do not support FTM. Non-L lenses with USM motors are identifiable by the striped gold ring printed around the end of the lens barrel."

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Reply #2 - Nov 15^th, 2007 at 1:02pm

Mictheslik Offline
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Me in G-LFSM :D
Bristol, England

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The focusing is much quicker, but personally, I don't notce a difference in noise....

I would reccommend USM, especially for aircraft/fast moving abject shots Wink