Canon EOS R5 C User Manual page 172

Wireless functions
You can use radio or optical wireless transmission to shoot with wireless multiple-flash
lighting.
For details on wireless flash, refer to the Instruction Manual of a Speedlite compatible with
wireless flash photography.
Firing ratio control (RATIO)
With a macro flash, you can set the firing ratio control.
For details on firing ratio control, refer to the Instruction Manual of the macro flash.
Flash zoom (flash coverage)
With Speedlites having a zooming flash head, you can set the flash coverage.
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