[AquilaEagle]

I'm looking around at Canon lenses for my 300d. I've seen 3 types of one lens.

EF75-300, EF75-300 USM and an EF75-300 IS USM

Now i know IS is the image stabaliser, but what does USM mean, and what is the difference between the non USM one and the USM one?

Thanks

[IanC_UK]

USM = Ultra Sonic Motor this is the motor used to autofocus and is suppoosed to be quicker, quieter etc than than the non USM types.

Wish i could offer a technical description ! lol

[AndyD]

USM stands for Ultra Sonic Motor. It refers to the focussing motor and means that it is quick and silent! :wink:

[AquilaEagle]

Thanks guys!

[AndyD]

welcome :wink:

[IanC_UK]

Bit of a SNAP moment there !

[AndyD]

:lol:

[AquilaEagle]

You must have both been very focussed

[IanC_UK]

Originally Posted by AquilaEagle

You must have both been very focussed

LOL silent and swift !


Damn thats a bad pun !!!!!! lol

[AndyD]

Ultra silent and Ultra swift (is this pun worse?) hahaha

:lol:

[IanC_UK]

Originally Posted by AndyD

Ultra silent and Ultra swift (is this pun worse?) hahaha

:lol:

Hmm thats as hard to call as the photo competition ! lol

[SDK^]

USM

In order to achieve critical autofocus, the elements within a camera lens have to move quickly, quietly, and with exacting precision. To accomplish this, Canon developed the world's first lens-based Ultrasonic Motor (USM). Based on a totally new technology, the motor spins by ultrasonic oscillation energy. In effect, instead of a large, noisy drive-train system, electronic vibrations created by a piezoelectric ceramic element power the mechanical action of the lens. In a very broad comparison, it's like the difference between a mechanical watch with gears and springs and quartz-timed watch movement. Therefore, torque is constant and start and stop functions virtually instantaneous.

By making the autofocus operation almost inaudible and by accelerating the autofocus speed, this type of motor greatly expands the shooting possibilities for Canon photographers. There is virtually no whining noise as the lens focuses to distract the subject or draw attention to the photographer. Most important for the photographer in the field, the motor draws minimal power so the camera batteries last longer.


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.

[Steve]

Canon really have hyped up the terminology there!!

Although I am a Canon user I would just like to point out that virtually all of the other major manufacturers have equivalent systems in their top end lens ranges. What they call it may differ but in use they are all much of a muchness. This feature alone does not offer enough performance difference to make a user of one system switch to another in my opinion.