NEWBIE QUESTION

[cgratti]

What does the USM mean on canon lenses?
What are the differences between all the lenses. I just ordered the D Rebel kit (hasnt arrived yet). I used to take photos with an OLD Pentax K1000 film camera, I am getting back into Photography, so figured I'd go with the D Rebel as a starter camera until I get my skills honed, then move up to a more pro camera.

Any help is appreciated in advance!

[tpinchback]

ultra sonic motor

[CyberDyneSystems]

What does the USM mean on canon lenses?

Like the man said,. Ultra Sonic Motor,. which means "really fast and almost silnet auto focus" to you and me :)

What are the differences between all the lenses.

Are you serious? Do you have a few days?
I think you need to do a little light reading on this one,. as there is just way to mutch to cover :)


I just ordered the D Rebel kit (hasnt arrived yet). I used to take photos with an OLD Pentax K1000 film camera, I am getting back into Photography, so figured I'd go with the D Rebel as a starter camera until I get my skills honed, then move up to a more pro camera.

Any help is appreciated in advance!

The DRebel is a great place to start with Digital. Film is free,. so take tones of pictures and call me in March :)

[Belmondo]

Both the previous posters have answered the USM question correctly. You will also see USM referred to in these threads regarding post-processing of images. In that context, we're referring to unsharp-masking, a method for sharpening images.

[cgratti]

Are you serious? Do you have a few days?
I think you need to do a little light reading on this one,. as there is just way to mutch to cover

I should have been more detailed, in that question. What I meant was what makes the USM special compared to the standard lenses? Do they focus faster? Are they clearer?

Thanks

[ilya]

Are you serious? Do you have a few days?
I think you need to do a little light reading on this one,. as there is just way to mutch to cover

I should have been more detailed, in that question. What I meant was what makes the USM special compared to the standard lenses? Do they focus faster? Are they clearer?

Thanks

Its a good question.

About 15 years ago, Canon started equipping its best lenses with the ring ultrasonic motor, in which the rotor and stator are big circles around the optics. These are incredibly fast and silent. Even more important, they allow simultaneous use of autofocus and manual focus. You can leave the lens in AF mode all the time and override the camera's decision at any time.

This is not to be confused with the Micro Ultrasonic Motor. Its 1/3 the cost. The micro ultrasonic motor is a tiny little motor that they stick in the lens and then connect with gears to the focus mechanism. A micro USM does not allow simultaneous AF and MF. Thus, the largest user-interface advantage of the ring USM is gone. Much of the noise of a standard motor is back too. The micro USM is noticeably quieter than a regular motor, but not silent like a ring USM.

How to check if the lens has USM or not when you have the lens in hand?

First, all USM lens sold by Canon do have the "Ultrasonic" logo and trademark printed on it. But that does not mean it is a real USM ring motor inside.

Second: all USM ring motor do have a window were you can read the focusing distance. Some USM micro-motor have it too, like the 75-300 USM II (IS or not). But if it has not the window, then it is not a USM ring motor either. Usually on those lenses, the focusing ring is just on the front element and usually thin. Why? Because the user probably won't focus manually either. It is consumer lens after all...

Third: USM ring motor lenses, when in AF mode, allow focusing manually. That means that if you turn the the focusing ring, the focusing distance you can read behind the small window will change accordingly. If it does not then you don't have a real USM ring motor on the lens.

[Nolz]

ilya!

thankyou so very much for the info...something i previously didnt know at all! and have wondered about...

i love this place :D

[EoSD30fReAk]

I've got some pictures from an USM ringmotor where Belmondo talked about. It's from a 28-135IS. No i haven't torn my lens apart :D

It's one of the many spare parts i got
thought you guys might like this so here they are!

http://img20.photobucket.com/albums/v59/EoSD30fReAk/Canon%20parts/usm_ringmotor_03.jpg

http://img20.photobucket.com/albums/v59/EoSD30fReAk/Canon%20parts/usm_ringmotor_02.jpg

http://img20.photobucket.com/albums/v59/EoSD30fReAk/Canon%20parts/usm_ringmotor_01.jpg