What are the advantages of USM/SWM?

[wuyongzheng]

Nikon is going to release AF-S 50mm f/1.4 to replace the older AF 50mm f/1.4D. Can someone enlighten me what the advantages of USM/SWM are? I know that the older one can't AF in Nikon D40/D60, but from the reaction on the internet, it seems there are a lot of people expecting/waiting for this AF-S version. I'm sure some of the people are not D40/D60 user. Why are non-D40/D60 users so happy with AF-S version?

Does USM focus faster and/or quieter than traditional motor? Is USM more energy efficient?

I've heard that the AF speed of the USM version of Tamron 17-50mm f/2.8 (Nikon mount) is slower than the older non-USM version. Except Tamron 17-50mm f/2.8, is there anyother case which compares USM and non-USM?

[ahguan]

USM and SWM are special fast motors with very low noise emission... Tamron version just means that the lens carries a motor for focusing, and is definitely not "supersonic" or "ultrasonic"

the other 3rd party lens maker i know who has such tech is the HSM by Sigma

[ortega]

canon usm
http://www.canon.com/technology/cano...ation/usm.html

sigma hsm
http://www.sigmaphoto.com/lenses/lenses.asp#hsm

nikon SWM
http://lens-reviews.com/component/op...0Wave%20Motor/

[wuyongzheng]

Originally Posted by ahguan USM and SWM are special fast motors with very low noise emission... Tamron version just means that the lens carries a motor for focusing, and is definitely not "supersonic" or "ultrasonic"

Thanks for the quick reply. I thought the Tamron lens uses ultrasonic motor. Now I understand why it's so noisy.