Canceling Speedlite Custom Function Settings
In step 1, select [Clear all Speedlite C.Fn's] to clear all the Speedlite's Custom Function settings (except [C.Fn-0: Distance indicator display]).
If you use an EX-series Speedlite and the Speedlite Custom Function's [Flash metering mode] is set to [TTL (autoflash)], the flash will always be fired at full output.