Canon 0020C003 Digital Camera User Manual

f: Changing the Autofocus OperationK
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 on continuously.
The exposure is set at the moment the picture is taken.
When the AF area selection mode is set to 19-point automatic
selection AF (p.114), the camera first uses the manually-selected AF
point to focus. During autofocusing, if the subject moves away from
the manually-selected AF point, focus tracking continues as long as
the subject is covered by the Area AF frame.
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 on in One-Shot AF, if the subject starts
moving, the camera will detect the movement, change the AF
operation automatically to AI Servo AF, and start tracking the moving
AI Servo AF for Moving Subjects
AI Focus AF for Switching the AF Operation Automatically
With AI Servo AF, the beeper will not sound even when focus is achieved.
Also, the focus indicator <o> in the viewfinder will not light up.
When focus is achieved with AI Focus AF with the Servo operation active,
the beeper will continue beeping softly. However, the focus indicator <o> in
the viewfinder will not light up. Note that focus will not be locked in this case.