Excerpt: You are looking at one of the most popular DSLR accessories available - a shoe-mount flash. The Canon Speedlite 430EX II Flash, at the time of this review, is Canon's middle child of standard Speedlite flashes. It contains a big amount of functionality , power and style in a modestly priced and sized body.
Excerpt: Why? Why use an external flash? The answer may be obvious to owners of camera bodies without a built-in flash, but not so clear to those using bodies with a built-in flash. The built-in flash is great for fill flash to light the shaded areas (such as people's eyes) in a pictures. To use fill flash, set your exposure for the ambient light, then dial in -1 to -2 EV FEC (Flash Exposure Compensation).