We've come a long way from the bang and puff of smoke you might see photographers using in silent movies. Instead, modern flash units use battery power to create electricity. This electricity produces a brief surge of light from a glass cylinder, which is filled with xenon gas.
In order to get action photographs that rival those of the pros, you're going to have to bite the bullet and spring for an electronic flash unit. The built-in flash on your camera won't provide the burst you need to capture images in motion. If you rely on it, you'll need to limit your shooting to outdoor events on sunny days or bump up the ISO setting on your camera. ISO is a numbering system, named after the International Standards Organization, that determines how "fast" or "slow" camera film is. Films with lower ISO numbers are slow, or less sensitive to light; films with high ISO numbers are fast, or more sensitive to light. A higher ISO setting, therefore, will allow more light to expose onto your film. Remember, however, if the ISO goes over 800, it'll probably produce a grainy image.
Nowadays you don't have to be a professional photographer to get a good flash photo. Sophisticated cameras and flash systems calculate all of the information to take a properly lit photo at an aperture within the flash's ability. If you're old-fashioned, you can calculate the distance that an electronic flash unit will let you shoot. Simply divide the flash unit's guide number for the ISO you plan to use by the maximum aperture of the lens [source: Shutterbug]. You can always increase the ISO number to give you a little more distance, or you can use a faster lens.
Professional action photographers enjoy experimenting with different combinations of flash and shutter speeds to get interesting effects. Slow-speed sync, high-speed sync and rear-speed sync are all potential techniques, depending on the desired image. More expensive flash units include a strobe feature, which allows the photographer to capture several points of motion at once. Flashes controlled by radio waves from the camera allow for synchronicity without any physical connection.
For longer-range action photography, you can purchase a tube that focuses the light from the flash. The angle of the view is narrowed, but the light is amplified, greatly increasing the distance you can be from your subject.