Canon EOS 40D Instruction Manual page 159

C.Fn III -3
0: Normal
Press the <S> button and use <9> to select the 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
The AF point in the viewfinder will not flash in red. Recommended when
it is bothersome to see it light up.
The AF point will still light when you select it.
C.Fn III -5
The AF-assist beam can be emitted by the camera's built-in flash or by the
external, EOS-dedicated Speedlite.
0: Enable
1: Disable
AF-assist beam not emitted.
2: Only external flash emits
If an external, EOS-dedicated Speedlite is attached, it will emit the AF-
assist beam when necessary. The camera's built-in flash will not emit
the AF-assist beam.
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 -5-0/2 is set.
AF point selection method
Superimposed display
AF-assist beam firing
3 Custom Function SettingsN
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