What does USM mean on a camera lens?
David Mack
Published Apr 27, 2026
Herein, what is the difference between USM and EF lenses?
For example, there are two Canon 24-70mm f/2.8L lenses: the first one is the Canon EF 24-70mm f/2.8L USM, and the other one is Canon EF 24-70mm f/2.8L II USM. The only difference in the name of the lenses is the “II” designation of the second lens, which means it is the newer, updated version.
Secondly, what is EF in camera lens? The EF lens mount is the standard lens mount on the Canon EOS family of SLR film and digital cameras. EF stands for "Electro-Focus": automatic focusing on EF lenses is handled by a dedicated electric motor built into the lens.
Herein, what is the difference between STM and USM?
USM stands for Ultrasonic Motor, while STM stands for Stepper Motor. Both are autofocus motors built into different lenses you'll find in Canon's lineup. By comparison, the STM lenses really are almost silent, as they were built with video in mind — rodents need not apply.
What is Nano USM lens?
Nano USM lenses use a motor system that combines the benefits of a ring ultrasonic motor (USM) with a lead-screw type STM (stepping motor). USM delivers high speed focusing for photo shooting, while STM allows for smooth and quiet focusing for video recording.