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Old Apr 7, 2005, 8:52 PM   #1
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What does the USM mean. i see this USM with certain lenses?
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Old Apr 7, 2005, 9:31 PM   #2
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I think it means Ultra Sonic Motor.

It means the zoom is quick and quiet.

Which is true, in comparison to other non-USM zooms.
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Old Apr 8, 2005, 2:25 AM   #3
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[email protected] wrote:
Quote:
I think it means Ultra Sonic Motor.

It means the zoom is quick and quiet.

Which is true, in comparison to other non-USM zooms.
survey says...... Ultra-Sonic Motor!!!!!

you win.

anyways, as terry said the USM is for Ultra-Sonic Motor, which refers to the focusing mechanism in the lens. Canons USM lenses are much quieter (almost silent) and much quicker than their non USM equicalents. if you are using a body that supports AI servo (continual) focusing mode i would definately spend the extra dough on the faster focusing lens.
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Old Apr 8, 2005, 9:30 AM   #4
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With the one caveat that Canon has now created two different "USM"s -- the Ring (the good, most expensive one, that allows continuous manual focus override without having to flip an AF/MF switch) and a Micro USM (which is actually just a small motor.

There are not a lot of advantages to Micro USM--- so when looking for USM lenses, make sure they're Ring USM.



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Old Apr 8, 2005, 6:08 PM   #5
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Isn't it true that ring USM lenses have the gold band after the word Ultrasonic, and the non-ring USM lenses just say Ultrasonic, with no ring?

Hmm, apparently that's not true, because the 50mm 1.4 has a gold band, but is a Micro USM. According to Canon: "Only lens in the EF System to combine the extra-small Micro USM and still provide full-time manual focusing"
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