Canon EOS 5D Instruction Manual page 198

3 Custom Function SettingsN
C.Fn III -3
0: Normal
Press the <S> button, then use <9> or <6/5> dial to select an AF
point.
1: Multi-controller direct
Without pressing the <S> button first, you can just use the <9> to
select the desired AF point. Pressing the <S> button will set it to
automatic AF point selection.
2: Quick Control Dial direct
Without pressing the <S> button first, you can just use the <5> to
select the desired AF point. By holding down the <S> button and
turning the <6> dial, you can set the exposure compensation.
C.Fn III -4
0: On
1: Off
When focus is achieved, the AF point will not flash in red in the
viewfinder. Recommended when it is bothersome to see it light up.
The AF point will still light when you select it.
C.Fn III -5
Enables or disables the EOS-dedicated Speedlite's AF-assist beam.
0: Enable
1: Disable
The AF-assist beam is not emitted.
If the external, EOS-dedicated Speedlite's [AF-assist beam firing] Custom
Function is set to [Disabled], the Speedlite will not emit the AF-assist beam
even if the camera's C.Fn III -5-0 is set.
198
AF point selection method
Superimposed display
AF-assist beam firing