Three-point lighting

Three-point lighting is a very common lighting technique used in both still photography and in film. By using three separate light sources, the photographer can illuminate the shot's subject (such as a person) however desired, while also controlling (or eliminating entirely) the shading and shadows produced by direct lighting.

The key light, as the name suggests, shines directly upon the subject and serves as its principal illuminator; more than anything else, the strength, color and angle of the key determines the shot's overall lighting design.

In indoor shots, the key is commonly a specialized lamp, or a camera's flash. In outdoor daytime shots, the Sun itself often serves as the key light. (In this case, of course, the photographer can't set the light in the exact position he or she wants, so instead arranges the subjects to best capture the sunlight, perhaps after waiting for the sun to position itself just right.)

The fill light also shines on the subject, but from a side angle relative to the key. It balances the key by illuminating shaded surfaces, and lessening or eliminating chiaroscuro effects, such as the shadow cast by a person's nose upon the rest of the face. Not using a fill at all can result in stark contrasts across the subject's surface, depending upon the key light's harshness. Sometimes, as in low-key lighting, this is a deliberate effect, but shots intended to look more natural and less stylistic require a fill.

In some situations a photographer can use a reflector (such as a piece of white cardstock mounted off-camera, or even a white-painted wall) as a fill light instead of an actual lamp. Reflecting and redirecting the key light's rays back upon the subject from a different angle can cause a softer, subtler effect than using another lamp.

The back light does not shine on the subject at all, but rather upon any surfaces behind the subject, in order to erase shadows cast by the subject as a result of the key and fill lights. A back light is most necessary if a vertical surface, such as a wall, is behind the subject. When there is no such background to catch cast shadows (such as in some outdoor shots), the back light might not be necessary.