All the receivers set at the same channel fire at the same output controlled by E-TTL autoflash to obtain a correct exposure.
Make sure the ST-E2's flash ratio control lamp is OFF.
(If necessary, press the <RATIO> button to turn it off. IF the flash ratio control lamp is on, the Speedlite may not fire or a correct exposure may not be attained. After turning off the flash ration control lamp, set the main switch to<HOLD> to prevent the flash ratio control lamp from lighting inadvertently.
