The impact of a filmed image is as dependent on lighting as it is on framing, composition, camera movement or any other element the filmmaker may control. Lighting allows the viewer to see the scene and directs his attention, since the eye is naturally drawn to bright areas of the frame. The direction from which light strikes an object or a face also influences how the object is seen. Side lighting casts shadows that emphasize depth, dimension and surface texture, while frontal lighting tends to flatten, compress and smooth over features. Also, the quality of light in a scene sets a mood, just as changes in the sky evoke various feelings. Painters are often celebrated for the way they manipulate light and create particular moods. Andrew Wyeth, for example, evokes the gray, quiet feeling of the Maine landscape with extremely flat and even illumination. Rembrandt creates a much more dramatic effect by using a “chiaroscuro” style, in which pools of light and shadow are used to obscure as much as they reveal of a subject. Cinematographers too are frequently known for a particular “look” that they achieve through their lighting technique.

    In fiction filmmaking, lighting is usually a top priority. Lights are positioned painstakingly, consuming much time and expense. The director of photography is usually responsible for the lighting design, which is as important as his mastery of cameras and lenses. In documentary filmmaking, light is sometimes treated in an auxiliary way, less for its mood than for its exposure value. In such films, lack of time or control over the film subjects often makes careful lighting impossible. Many films are made entirely in available light, with no additional lighting introduced by the filmmakers. Artificial lighting is often needed to reduce the contrast of a scene so that it can be rendered properly on film.

    The shadows cast by a light source are determined by its hardness. Hard light, also called specular light, like direct sunlight on a clear day, is made up of parallel rays that produce clean, hard shadows that neatly outline the shapes of objects. The soft, or diffuse, light of a hazy or overcast day is less directional; it emanates from all parts of the sky at once. If it casts shadows at all, they are dull and indistinct.

    Hard light can be produced artificially with lensed or focused lamps that emit a clearly directed beam. The spotlights used to single out a performer on stage are extremely hard. Soft light is usually made by bouncing lamp light on a white or silvery surface that is often scoop shaped. Soft light creates a broad and even glow, not a beam of light.

    Because hard light casts distinct shadows, it is used to delineate shapes. It brings out surface textures and the contrast between areas of different color or tonal value, but when used alone it tends to be harsh. Hollywood often uses hard lights on male actors to bring out rugged facial features.

    Hard light can be produced with relatively compact lighting fixtures. The key light on a film set is usually hard, the key functioning as a primary source of illumination that casts bold shadows and gives the impression that the lighting in the scene comes mostly from one direction.

    Soft light relatively gentle and tends to smooth out features and textures. Traditionally, female actors are lit with soft light to disguise and facial wrinkles or imperfections. A single soft light off to the side can provide delicate modeling of curved surfaces such as the face, because of the way it “wraps around” the curve with gradual shading, hard lights would produce shading that is more sharp edged.

    Soft light fixtures are used on the set as fill lights to fill in the shadows cast by harder lights without adding more shadows of their own. Soft lighting has become increasingly popular in fiction filmmaking and television commercials. It is sometimes claimed that soft lighting looks more natural.