Canon Speedlite 470EX-AI Instruction Manual page 69

Zoom (flash coverage)
You can set the Speedlite flash coverage. When [Auto] is selected,
the flash coverage is set automatically according to the focal length
of the shooting lens and the image sensor size of the camera (p.26).
Clear settings
When [Clear flash settings] or [Clear external flash set.] is
selected, you can revert the settings of Speedlite to their default
settings.
If the flash coverage is automatically set such as when the bounce adapter
is attached or the wide panel is used, or when the <X> switch is set to
the <Z> position, setting [Zoom] (flash coverage) is not possible.
[Flash firing] and [E-TTL II flash metering] are displayed in step 2 or
step 3 on page 66. (Display layouts and procedures vary by camera
model.)
When [Flash sync. speed in Av mode] is not displayed, it can be set
with the camera's Custom Functions.
When the flash exposure compensation is set on the flash, flash
exposure compensation cannot be performed from the camera. If both
are set at the same time, priority is given to the setting on the flash.
Flash Control from the Camera's Menu Screen
69