Camera flash units help you light scenes for better photos.
Ever since the use of flash powder to light up a scene for slow image plates in the 19th century, photographers have used the sudden burst of light to make their photos possible. When plates changed to film, the media still was very slow, meaning the light-sensitive material took some time to capture light. Film emulsions got faster, but photographers often still needed to supplement available light. With the transition to digital cameras, you still need a flash in many circumstances.
Fill Flash
Almost all modern cameras have a small built-in flash called a fill flash. Whether you use a simple point-and-shoot camera or an expensive digital single-lens reflex camera, this flash is available. As the name implies, this kind of flash works to fill in shadows slightly. For example, if you are shooting an image of a newly married couple on a sunny day, shadow may fall on their faces while all around them is bright. The fill flash is designed to provide enough light to fill in the shadow and brighten the faces without looking like a glaring, bright and unnatural flash of light.
Direct Flash
Direct flash is the type of electronic flash unit that sits directly atop medium- to high-end cameras such as DSLRs. This kind of flash unit attaches to the camera through an accessory shoe on top of the viewfinder. In most cases, it connects electronically to the camera through a contact in the base of the shoe. You also can connect this type of flash with a small cord. Because the flash sits directly on top of the viewfinder, the line of the flash is directly at your subject. This gives a wide area of light to cover your image field. It is the most common DSLR accessory, especially for those photographers who need extra power in their flash for indoor subjects. The main problem with this common flash is that if you photograph people with it against a dark background area, their retinas may reflect the light through their open irises and produce "red eye," in which their eyes appear bright red.
Bounce Flash
Bounce flash solves the problem of red eye and also allows for less direct lighting. A bounce flash typically looks the same as a direct flash except that the flash head pivots to varying degrees. This allows you to bounce the flash off the ceiling or a wall if you turn the camera vertically. The result is softer lighting because no direct flash reaches your subject. You can use the different angles to adjust how the light falls on your subjects.
Bracket Flash
Mostly professional photographers use a flash bracket. It makes the camera heavier and a bit unwieldy, while at the same time giving it a little more stability. The bracket attaches to the camera, usually through the tripod socket. It holds your electronic flash unit off to the side of your camera. This works as a compromise between direct and bounce flash. While the flash is directly toward your subjects, it is not in a direct line with the lens, but off at an angle. This usually cuts down red eye and allows for more overall illumination of the scene.
Tags: bounce flash, flash unit, attaches camera, camera through, direct flash