Canon EOS 60D Instruction Manual page 39

Custom Function Settings*
O: On
1: Off
When focus is achieved, the AF point will not light up in red in the
viewfinder. Set this if the AF points lighting up is too distracting.
The AF point will still light up when you select it.
The AF-assist beam can be emitted by the camera's built-in flash or by an
external, EOS-dedicated Speedlite.
O: Enable
1 : Disable
The AF-assist beam is not emitted.
2: Enable external flash only
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 fire the
AF-assist beam.
3: IR AF assist beam only
Among EOS-dedicated Speedlites, only those which have an infrared
AF-assist beam will be able to emit the beam. This prevents any
Speedlite which uses a series of small flashes (like the built-in flash)
from firing the AF-assist beam.
[] if the external; Eos;dedicated Speedlitels [AF,assist beam firing] custom
Eunction iS Set to [Disabled], the Speedl!te w!ll not emit the AE-assist beam
even if the camerals C,Fn !!! -4-0/2/3 is set,
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