Hi,

Can anyone tell me the full benefits of USM .v. non-USM lenses? I am thinking of purchasing the Canon EF 28-200mm f/3.5-5.6 lens.

-- David J McLaren (davidjmclaren@yahoo.co.uk), November 01, 2001

Answers

Check here: http://www.photo.net/photo/canon/lens-motors

The 28-200 USM uses a micro motor, not the ring-type USM motor used in the 28-105, 24-85, 28-135IS, certain prime lenses, and most L lenses.

-- Kenneth Katz (socks@bestweb.net), November 01, 2001.

You can also check out Canon's EF lens technology page. They have recently updated thier site to include more information on their EF line up. http://www.usa.canon.com/eflenses/technology/index.html

-- Derrick Morin (dmorin@oasisol.com), November 01, 2001.

I have resolved never to buy another non-Ring USM lens again. I've had micro-USM and third party non-USM AF lenses. Ring USM (especially with an EOS 3 or EOS 1V) blows away the competition.

-- Isaac Sibson (isibson@hotmail.com), November 01, 2001.

USM lens focus by ultrasonic motor which canon says is quiet or even silent.But it is very intuitive whether a lens is quiet or not. A non-usm lens can also be 'quiet'. but if u care a lot about the sound made by the focusing action of the lens,eg.shooting in church,musical performance...then buy the usm version at a higher cost. u can focus manually as a last resort.

-- legnum (legnum212@email.com), November 04, 2001.

How can you know when shopping for an USM lens whether it is micro- USM or ring-USM? I'm looking at B&H web site and can't see any information about this. Particularly the 20-35 f/3.5-4.5 USM. Thanks!

-- Christian Erickson (christian@tenbyten.com), November 05, 2001.

Christian:

I have the 20-35 USM, and it has a ring type USM motor. Its a very nice lens.

For a complete list, get on Canon's web site and request their lens brochure, since it provides a detailed description of each lens It should take no longer than 2 weeks to get it. The information here: "http://www.tanchung.com/canon/index.htm" should have what your looking for. This site is also useful "http://www.canon.com/camera- museum/"

In general, except for the 75-300IS and 28-200USM, the other micro USM zoom lenses are inexpensive (Under $200).

-- Kenneth Katz (socks@bestweb.net), November 06, 2001.

All USM lenses with a plastic lens mount are micro-USM, while almost all metal-mount USM lenses are Ring USM. The only metal-mounted USMs which are micro-USM are the 28-200USM, 75-300 USM, 75-300 IS USM and the 50mm F1.4 USM (I think...if I missed any, let me know...).

In use, how can you tell? The micro-USM is not silent, although a lot quieter than other lens motors, and it does not offer FTM (except the 50mm F1.4...not sure how they did that). Ring USM is silent and faster than micro-USM.

-- Isaac Sibson (isibson@hotmail.com), November 06, 2001.

i think that's because the 50mm f/1.4 is a ring-usm lens...

-- jeff nakayama (moonduck22@hotmail.com), December 11, 2001.