- One-shot autofocus is the name of Canon's Single-Servo autofocus system, that focuses on a subject once, and then stops focusing. The acquisition of a focus lock is often indicated by a beeping sound from the camera. The photographer is able to then fully press the shutter release and capture images, and/or re-compose their framing. The autofocus system will stay locked until the photographer removes their finger from the shutter release and presses it again.
This autofocus mode is useful for photographing any static scene, or a subject that is not moving.