Beeper - Canon EOS 1D Mark III Instruction Manual

If focus cannot be achieved, the focus confirmation light <o> in the
viewfinder will blink. If this occurs, a picture cannot be taken even if the
shutter button is pressed completely. Recompose the picture and try and
focus again. Or see "When Autofocus Fails" (p.86).
If the [2 Beep] menu is set to [Off], the beeper will not sound when focus is achieved.
Focus Lock
After achieving focus with One-Shot AF, you can lock the focus on a subject
and recompose the shot. This is called "focus lock." This is convenient when
you want to focus a subject not covered by the Area AF.
AI Servo AF for Moving Subjects
Focus Tracking with AI Servo AF
If the subject approaches or retreats from the camera at a constant rate, the
camera tracks the subject and predicts the focusing distance immediately before
the picture is taken. This is for obtaining correct focus at the moment of exposure.
When the AF point selection is automatic (p.84), 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 the Area AF.
With a manually selected AF point, the selected AF point will focus
track the subject.
With AI Servo AF, the beeper will not sound even when focus is achieved. Also,
the focus confirmation light <o> in the viewfinder will not light.
This AF mode is 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.
AF is also possible by pressing the
<p> button.
E: Selecting the AF Mode
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