Canon SPEEDLITE EL-1 Advanced User's Manual page 101

2.
Set the Custom Function.
Select the Custom Function number (1), then set the function.
To clear all the Custom Function settings, select [Clear settings] in
step 1, and select [Clear all Speedlite C.Fn's] or [Clear ext. flash
C.Fn set.].
Caution
When using a camera released in 2011 or earlier, or with
EOS REBEL T100/4000D/3000D, EOS REBEL T7/1500D/2000D,
EOS REBEL T6/1300D or EOS REBEL T5/1200D, the C.Fn-21 to 23 settings are
not cleared even if [Clear all Speedlite C.Fn's] or [Clear ext. flash C.Fn set.] is
selected. When the procedure described in "Clearing All the Custom/Personal
Functions" on page is performed (
are cleared.
Personal Functions (P.Fn) cannot be set or all cleared at once from the camera's
menu screen. Set them by operating the flash.
), all the Custom Functions (except C.Fn-00)
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