Three-point lighting is the standard lighting scheme in motion pictures or still photography. The three sources of light a technician uses, or the three "points," are the key light, the fill light and the rim light. The key light is usually the strongest light of the three. This light has the most flexible positioning in relation to the subject to be lit and can add a great measure of visual meaning to the final composition of a shot. The fill light is a softer light source than the key because it has the opposite purpose of flooding shadows instead of creating them. Finally, the rim light is typically placed behind the subject to create a subtle contrast between the setting and the subject the camera is focused upon. The rim light produces a three-dimensional look. A lighting technician may choose to remove any one of these lights to achieve a more dramatic effect.
The rim light helps a viewer focus on the subject of a scene. Like a soft focus, the rim light helps in drawing a spectator's eye to the place the photographer intended. It also creates an attractive silhouette when a photographer may want to shoot the subject entirely in shadow against a well-lighted background.
Without exaggeration, every major motion picture includes a scene with a rim light. Likewise, many movie posters feature subjects with multiple rim lights and incidental. In the movie poster for "Iron Man," for example, actor Robert Downey Jr. is rim lighted by a search helicopter's light. This creates a contrast between Downey Jr. and the ominous backdrop of Iron Man in costume. An explosion behind actor Gwyneth Paltrow creates a similar rim contrast between Paltrow and Downey Jr. in the same poster, giving the artwork an added depth of field.
There is a big difference in how rim lighting is done in black and white films and photographs as opposed to color photography. One photographer, Sarah Fox, notes how early Hollywood films reveal a much starker contrast as a result of harsher shadows created by harsher lighting in the totally monochromatic age. With the progression to color and the subsequent technological advancements in definition, rim lights have become a more delicate light source. This does not mean, however, that photographers and lighting technicians follow any one set of rules in determining how bright, how soft, how dull or how harsh any given light on a set will be. Any or all of these standards may be abandoned. Consistency can be achieved using a color meter.
Another commonly used name for the rim light is the back light or hair light. These are understandable monikers as the rim light is placed to the back of the subject, and when the subject is a person, the glow the lighting produces falls about the individual's hair or head.