USM lenses

[Camper Dave]

hi folks,

my first post!

bit of anewbie question this, but what's the difference between a USM and a non USM lens? and what does it stand for? i'm looking at a new telephoto lens for my camera and it's become a bit of a sticking point.

thanks in advance
dave

p.s. nice site!

 

[Big Mike]

USM --> Ultra Sonic Motor. It's the motor that moves the elements to focus the lens.

USM is great feature to have on a lens. The focus is quicker and much quieter.

Non-USM lenses, I think they use gears to focus.

Also, I think (but I'm not sure) that with USM lenses you can simply turn the focus ring to manually focus...while with Non-USM you have to flick a switch before you can use the focus ring.

 

[Camper Dave]

cheers dude

think i might drift toward the USM one then if it's a quicker focus.

thanks again,
dave

 

[markc]

Canon was a bit deceptive with this, though. Not all USM motors are equal. The ring USM lenses are the ones that are the quickest and the quietest.

 

[Camper Dave]

cheers for that marc, it's a canon i've got. i'll have to keep an eye on that when looking. seems a bit sly selling two different 'types' under one name.