Canon EOS 600D - Manual (Page 180)

180
The built-in flash and external Speedlite settings can be set with the
camera’s menu. You can use the camera’s menu to set the external
Speedlite function settings only if the attached EX-series Speedlite is
compatible with this function.
The setting procedure is the same as setting a camera menu function.
Select [Flash control].
Under the [1] tab, select [Flash
control], then press <
0>.
X The flash control screen will appear.
Normally, set this to [Enable].
If [Disable] is set, neither the built-
in flash nor the external Speedlite
will fire. This is useful when you only
want to use the flash’s AF-assist
beam.
For normal flash exposures, set this
to [Evaluative].
[Average] is for advanced users. As
with an external Speedlite, the
metering area is averaged. Flash
exposure compensation may be
necessary.
3 Setting the FlashN
[Flash firing]
E-TTL II Metering Modes
Even if [Flash firing] has been set to [Disable], if focus is difficult to achieve
in low light, the built-in flash may still fire a series of flashes (AF-assist
beam, p.86).