Canon EOS 5D Mark III Instruction Manual (en)

82: Custom Controls
When you press the button assigned to this function, metering and AF 
are executed.
*1: If you assign the [Metering and AF start] function to the <p> and <A> 
buttons and add the function to switch to the registered AF point, you can instantly 
switch to the registered AF point. To enable this function, press the <
B> button in 
step 3 on page 327. On the [AF start point] selection screen, select [Registered AF 
Registering and using an AF point
1. Set the AF area selection mode to one of the following: Single-point 
Spot AF, Single-point AF, AF point expansion (manual selection, 
surrounding points), or 61-point automatic selection AF. (Zone AF 
cannot be registered.)
2. Select an AF point manually (p.74).
3. Hold down the <S> button and press the <U> button. A beep will 
sound and the AF point will be registered. If the AF area selection 
mode is not set to 61-point automatic selection AF, the registered AF 
point will blink. 
If [24: Orientation linked AF point] is set to [Select separate AF 
], you can register the AF point separately for the vertical 
(camera grip at top or bottom) and horizontal orientations.
4. When you press the <p> button assigned to this function or 
press the <A> button, the camera will switch to the manually-
selected AF point when you registered. 
To cancel the registered AF point, hold down the <S> button and 
press the <m> button. The registered AF point will also be 
canceled if you select [54: Clear all camera settings].
: Metering and AF start
When an AF point is registered, the following will be displayed:
• 61-point automatic selection AF: 
• Single-point Spot AF, Single-point AF, AF point expansion: SEL 
(Center)/SEL HP (Off-center)
When registered with SEL  
SEL HP, the registered AF point will blink.