Canon SPEEDLITE EL-1 Advanced User's Manual page 193

Stroboscopic Flash
Set the stroboscopic flash settings. For details on the setting procedure, see
Flash".
Caution
The flash frequency when performing stroboscopic flash during optical transmission
wireless shooting can be set from 1 Hz to 199 Hz (settings from 250 Hz to 500 Hz
are not available).
Note
A receiver unit that is set as an individual receiver unit cannot be subject to flash
mode control from the sender unit. The receiver unit fires in the flash mode that is
set by individual receiver.
193
"Stroboscopic