Canon SPEEDLITE EL-1 Advanced User's Manual page 151

Caution
Modeling flash is not possible from a receiver unit with cameras released up to
2011 or with EOS REBEL T100/4000D/3000D, EOS REBEL T7/1500D/2000D,
EOS REBEL T6/1300D or EOS REBEL T5/1200D.
For the precautions related to modeling flash, see
When C.Fn-02-1 is set on the sender unit (
if you select <
Note
If there are two or more sender units (
sender.
>.
), the flash signal is sent to the main
151
"Modeling Flash".
), modeling flash will not be fired even