Canon® EOS Digital Photography Photo Workshop

8.3. CANON'S SPEEDLITE LINEUP

Canon's dSLR accessory flash brand is called Speedlite (not to be confused with Nikon's Speedlights). These powerful and sophisticated flashes, with the 580EX II as the flagship model, are filled with features that provide virtually any flash capabilities you'll need short of moving to external studio lighting. For instance, the ability of multiple flashes to integrate as "master" and "slave" units (where one flash causes others to fire wirelessly) means you can set up virtual, portable studiolike lighting almost anywhere. And the power of the flashes has increased to the point that the bulky, heavy third-party flashes that so commonly burdened the traditional wedding photographer are virtually obsolete. Furthermore, flash recycle times are vastly improved from what they used to be and, as batteries have also improved, there's less need for external battery power sources, as well.

While the name "Speedlite" is a branded term, the specific model number refers directly to the flash's guide number, which is the measurement of the flash's power; higher guide numbers mean a more powerful flash. A guide number tells you how well your flash will be able to illuminate a given area at maximum flash-to-subject distance (typically measured in meters).

For example, Canon's 580EX II has a maximum guide number of 58 meters at a 105mm focal length setting and the 430EX has a guide number of 43. Internally, the guide number is a calculation made by the flash's on-board ...