Canon EOS-1D X Mark III Advanced User's Manual page 860

: Metering and AF Start
Pressing the button assigned to this function starts metering and AF.
* 1: When the <
setting screen displayed enables you to set detailed AF settings. Pressing the <
< > button as you shoot starts AF under the configured settings.
AF start position
When set to [Registered AF point], pressing the <
to the registered AF point.
Registering the AF point
1. Set the AF area selection mode to one of the following: Spot AF, 1-point AF, Expand
AF area:
Zone AF are not available.
2. Select an AF point manually.
3. Hold down the <
camera beeps and registers the AF point. The registered AF point blinks unless you
have set the AF area selection mode to an option other than Auto selection AF.
Note
The following information is displayed when an AF point is registered.
• Auto selection AF:
• Spot AF, 1-point AF, Expand AF area: (manual selection), or Expand AF
area: Surround:
To clear registered AF points, hold down the <
< > button.
AI Servo AF characteristics (
Pressing the <
specified case [Case *].
AF operation (
Pressing the <
> or < > button is assigned, pressing the <
, Expand AF area: Surround, or Auto selection AF. Zone AF and Large
> button, then press the <
(center)/
)
> or < > button starts AF with characteristics of your
)
> or < > button starts AF with your specified AF operation.
> button, after which the
(HP: home position)
(other than center)
> button and press the
860
> button with the
> or < > button switches
> or