Canon Xsi Instruction Manual page 117

E-TTL II
For normal flash exposures, set it to [Evaluative].
If [Average] is set, the flash exposure will be averaged for the entire
metered scene as with an external metering flash. Flash exposure
compensation may be necessary depending on the scene, so this is
for advanced users.
Setting the External Speedlites
Select either [External flash func. setting] or [External flash C.Fn
setting]. For details on which external Speedlite settings the
camera can set, see the compatible EX-series (such as the 580EX II)
Speedlite's instruction manual.
Attach the Speedlite to the camera and turn on the Speedlite.
External flash func. setting
External flash C.Fn setting
Select either [External flash func.
1
setting] or [External flash C.Fn
setting].
Select either one, then press <0>.
Settings which cannot be set will be
dimmed.
Set the external flash function settings.
2
Select a flash function and set it as
desired. The procedure is the same
as setting a menu function.
On the flash function settings screen,
the settable items, current settings,
flash mode setting, and flash Custom
Function settings might look different
on your camera.
If you press the <B> button to
clear the Speedlite settings, both the
external Speedlite and built-in flash
settings will be cleared.
3 Flash ControlN
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