Canon Lenses - USM vs DC

[Podie]

I'm looking at Canon EF 75-300 mm f4/5.6 Mk3 lenses… and there are two versions available… one with a USM (ultra sonic motor?) and one with a DC motor. What's the difference between the two (cost aside) and which am I best purchasing if most of my photos will be of scenery or moving objects..? (eg cars and animals)

TIA.

[simpo two]

USM every time (or HSM in Sigma-speak).

[Bee_Jay]

USM is faster, quieter.

Some people refer to USM to mean you have full-time manual adjust aswell...

[bga]

I have found my canon USM lens much faster & quieter when autofocussing than my canon DC lens. The DC seems ponderous in comparison

[Podie]

Thanks... seems odd that the USM lens is circa £20 cheaper then...!!

[nighthawk]

Not all the USM lenses are the same though, I have the 75-300 IS usm and it's not capable of full time manual focusing, it's also noiser and slower than the Ring type USM system on my 17-40 L

All that considered the USM on the 75-300 kicks the @rse of the non USM lenses in the range.

[SDK]

There are two types of USM Focus systems – Micro and Ring-type.

Ring-type USM-equipped lenses, found in large aperture and super telephoto designs, allow manual focusing without switching out of the auto mode.
Micro USM designs bring the performance benefits of Canon's USM technology to a wide assortment of affordable EF lenses. Extremely compact and light.

[simpo two]

SDK said:

Micro USM designs bring the performance benefits of Canon's USM technology to a wide assortment of affordable EF lenses.

You didn't write the brochure by any chance?