Canon EOS Rebel T4i Instruction Manual - Page 96

f: Changing the Autofocus OperationN If focus cannot be achieved, the focus confirmation light in the viewfinder will blink. If this occurs, the picture cannot be taken even if the shutter button is pressed completely. Recompose the picture and try to focus again. Or see "Subjects Difficult to Focus" (p.100). If [z1: Beep] is set to [Disable], the beeper will not sound when focus is achieved. AI Servo AF for Moving Subjects This AF operation is suited for moving subjects when the focusing distance keeps changing. While you hold down the shutter button halfway, the subject will be focused continuously. The exposure is set at the moment the picture is taken. When the AF point selection (p.97) is automatic, the camera first uses the center AF point to focus. During autofocusing, if the subject moves away from the center AF point, focus tracking continues as long as the subject is covered by another AF point. With AI Servo AF, the beeper will not sound even when focus is achieved. Also, the focus confirmation light in the viewfinder will not light up. AI Focus AF for Automatic Switching of AF Operation AI Focus AF switches the AF operation from One-Shot AF to AI Servo AF automatically if a still subject starts moving. After the subject is focused in One-Shot AF operation, if the subject starts moving, the camera will detect the movement, change the AF operation automatically to AI Servo AF, and keep tracking the moving subject. When focus is achieved in the AI Focus AF operation with the Servo mode active, the beeper will sound softly. However, the focus confirmation light in the viewfinder will not light up. Note that focus will not be locked in this case. 96