What is USM?

An ultrasonic motor lens has a motor built into the lens body that enables the lens to focus faster. The USM technology requires very little power and is extremely quick.

USM Types

There are two types of USM from Canon: a ring ultrasonic motor, designated FTM (full-time manual focus), and a micro ultrasonic motor. The FTM system is used on Canon's best lenses and is noticeably quieter than other lenses; it also allows the photographer to use auto focus and manual focus at the same time. The micro USM is not as quiet as the FTM, and does not allow simultaneous auto focus and manual focus.

What Types on What Lenses

Canon uses FTM on its super telephoto lenses and on large aperture lenses, where the speed advantage is noticeable. Canon uses micro USM on its compact lenses, which allows Canon to create smaller lenses that still focus quickly.

Uses

USM lenses are useful for sports and action photographers, who need a faster-focusing lens. FTM type lenses are especially useful for wildlife photographers, who want to be able to focus and shoot quickly while not spooking the wildlife.

Disadvantages

USM lenses, whether they are micro USM or FTM, are more expensive than non-USM lenses and can also be heavier.

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What Does USM Mean

About USM