Canon Speedlite 600EX II-RT Manual (en)

Flash Control from the Camera’s Menu Screen
You can set Custom Functions for the Speedlite from the camera’s 
menu screen. The details displayed vary by the camera. If C.Fn-20 to 
23 are not displayed, set them by operating the Speedlite. For the 
Custom Functions, see pages 113-117.
Select [Flash C.Fn settings].
Select [Flash C.Fn settings] or 
[External flash C.Fn setting].
The flash Custom Function settings 
screen is displayed.
Set the Custom Function.
Select the Custom Function number, 
then set the function.
To clear all the Custom Function 
settings, select ([Clear settings],) 
[Clear all Speedlite C.Fn’s] or [Clear 
ext. flash C.Fn set.
] in step 1.
Flash Custom Function Settings
Custom Function number
When using a camera released in 2011 or earlier, or with EOS REBEL 
T6/1300D or EOS REBEL T5/1200D, the C.Fn-20 to 23 settings are not 
cleared even if [Clear all Speedlite C.Fn’s] or [Clear ext. flash C.Fn 
] is selected. When the procedure described in “Clearing All the 
Custom/Personal Functions” on page 112 is performed, all the Custom 
Functions (except C.Fn-00) are cleared.
When using the flash with EOS DIGITAL cameras released in and after 
2012, as auto external metering and manual external metering can be 
directly selected with the flash’s <E> button, C.Fn-05-2, 3 are not 
selectable (except with EOS REBEL T6/1300D and EOS REBEL T5/1200D).
Personal Functions (P.Fn/p.118) cannot be set or all cleared at once from 
the camera’s menu screen. Set them by operating the Speedlite.