Three types of studio light put the photographer in control of the result.
Portrait photographs seem to have infinite variations, yet when it comes to studio portraits, lighting can be broken down to three types. It is how these types are combined and utilized by the photographer that the multitude of effects are created. Some arrangements of lighting might be chosen to flatter the model's face, while others may highlight the clothes she wears.
Fill Light
The fill light provides the basis for the photograph. It is generally located about the same place as the photographer and provides general illumination of the scene. It will fill shadows, smooth complexions and perhaps light props. It is most often a diffuse light, reflected off an umbrella or shone through a soft box. The brightness of the fill light relative to the main light is referred to as the lighting ratio.
Main Light
The main, or "key" light provides directionality. This light is to the side of the model. The angle decides what effect the main light will have. It can be located close to the fill light for even, flat lighting or the angle can be increased to 90 degrees at the model's side, or beyond. The main light is the brightest of the three types, and provides the highlights in the final photograph.
Background Light
The background light serves two purposes: to separate the model from the background and to set the brightness (or darkness) of the background itself. The light may be directed onto the background or on to the back of the model. Careful placement of the background light can take an even toned backdrop and make it a smoothly graduated surface, moving from light to dark. Effective use of the background light gives a sense of depth to a photograph.
Reflectors
Though not a type of light in itself, the use of reflectors is crucial to getting the most out of studio lights. A reflector could be anything from a small piece of white cardboard held beside a model's face to a full length sheet of foam core. A reflector can replace a fill light in some types of shots, reflecting the main light into shadow areas that the light itself does not reach. Reflected light has a soft, flattering effect that is useful in portraits.
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