DPChallenge: A Digital Photography Contest
 

DPChallenge Forums >> General Discussion >> Canon Lense Terminology
⏮️⏪◀️ 1/1 ▶️⏩⏭️
Showing posts 1 - 2 of 2, (reverse)
AuthorThread
Canon EOS R5
Canon RF 100-500mm f/4.5-7.1 L IS USM
 10/29/2004 07:22:39 PM · #1
Can anyone tell me what the Canon Lens terminology means? AF vs EF vs USM? I assume AF is autofocus and the USM is ultrasonic motor, but what are the differences and which is best?
Canon EOS-10D
Canon EF 17-40mm f/4.0 L USM
 10/29/2004 07:42:41 PM · #2
EF is the lens mount. Electronic USM is the type of motor which drives the autofocus, as opposed to a non-USM motor which doesn't have full time manual focus.

Most things are explained in this document:

Canon EF Lens Chart (PDF)

Originally posted by rodneyg:
Can anyone tell me what the Canon Lens terminology means? AF vs EF vs USM? I assume AF is autofocus and the USM is ultrasonic motor, but what are the differences and which is best?

⏮️⏪◀️ 1/1 ▶️⏩⏭️
Current Server Time: 09/22/2026 07:38:59 PM

Please log in or register to post to the forums.
Theme: Classic / Light / Dark
Home - Challenges - Community - League - Photos - Cameras - Lenses - Learn - Help - Terms of Use - Privacy - Top ^
DPChallenge, and website content and design, Copyright © 2001-2026 Challenging Technologies, LLC.
All digital photo copyrights belong to the photographers and may not be used without permission.
Current Server Time: 09/22/2026 07:38:59 PM EDT.