Canon Speedlite 600EX-RT Instruction Manual page 47

Zoom (flash coverage)
You can set the flash coverage for the Speedlite. When [Auto] is
selected, the flash coverage is set automatically according to the
focal length of the lens.
Wireless flash functions (setting)
You can perform wireless flash shooting. Two wireless flash shooting
methods are available; radio transmission and optical transmission.
For details, see Chapter 4 and Chapter 5.
Clear Speedlite (function) settings
You can return the flash settings to their default settings.
When flash exposure compensation is set on the flash, you cannot set flash
exposure compensation in the camera's menu screen. Note that if both are
set at the same time, the setting on the flash is given priority.
Flash Control from Camera's Menu Screen
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