The easiest way to get your external flash (Speedlite) off-camera, if you own a Canon DSLR with a built-in or pop-up flash is by following the instructions on the videos below. This is triggering via Optical or Infrared mode with older Canon 550EX, 580EX, 430EX, 580-EXII & 430EXII Speedlites.
Note, it doesn’t matter if you set your Speedlite first or the camera body first. The most important thing is the Channel number. The camera body and the Speedlite has to be set to the same channel.I set my Speedlite and my camera body to Channel 3 because the default is Channel 1.
On the camera body
Setting up your Speedlite and Built-in Pop-up Flash to fire in ETTL mode.
On the Speedlite
Okay after you’ve played around with the ‘Auto’ or “ETTL” mode and you’ve mastered what that can do, it is time to take control and really be in charge. With the flash mode from “ETTL” to “Manual”.
You will notice a huge difference in your camera battery life for one thing. The other? Your external Speedlite batteries will last even longer because Manual flash doesn’t fire a pre-flash. Also you can probably trigger other flashes if they have an optical eye. In other words the possibilities are limitless as to how many you can use.