Canon Speedlite Flashes Are Named After Their Guide Numbers
This is probably a "duh" fact for many of you, but one that some of you have perhaps never heard or realized before: Did you know that the flashes in the Canon Speedlite lineup are named after their maximum guide numbers? To figure out the power of your Speedlite, just take the model name and hack off the zero at the end to get the GN (e.g. 430EX has GN 43, 580EX has GN 58).
