STM (Canon)

STM stands for stepper motor lenses, a new type of autofocus motor used by Canon in some of its lenses. Stepper motors offer fast, precise and quiet focus adjustments, so these lenses are well suited both to regular stills photography and to video, where autofocus noise can be picked up very easily by the camera’s internal microphone. Canon’s STM lenses work very effectively with cameras using Canon’s Dual Pixel CMOS AF autofocus system.

See also: Autofocus basics