The direction of illumination greatly determines how the subject appears on the screen. Light striking the subject from the direction of the camera is called front light. Front axial light, which emanates from very near the camera’s lens, casts shadows that are mostly not visible from the camera position but may unpleasantly outline a subject standing in front of a wall. Camera-mounted fixtures, such as those used for flash photography, provide front light, which illuminates all the visible surfaces of the subject. Full frontal lighting is usually uninteresting, since no modeling shadows are visible and dimensionality and surface texture are minimized. The flattening effect may, however, be desired.

    You can think of full frontal lighting as projecting from the number 6 on a clock face whose center is the subject. (Think of the camera as also positioned at the number 6.) Offset (the light at number 5 or 7) and three quarter front light (around 4:30 or 7:30) can be used for portraiture when more shadowing is desired.

    Full side light (around 3 or 9) provides good modeling and indication of texture (since texture is indicated by the pattern of tiny individual shadows visible from the camera position). Side light can be quite dramatic. It produces shadows that fall clearly across the frame and distinctly reveal the depth of various objects in space.

    Back light originates from behind (and, in studio lighting, usually above) the subject. It tends to outline the subject’s shape and to differentiate it from the background. Backlight can produce a bright edge or halo on a subject’s hair and shoulders. When back light predominates, called contre-jour, it can create a moody and romantic effect, giving a sense of isolation to the subject. If the background is bright and no light falls on the camera side of the subject, the subject will be in silhouette.

    The effect of lighting is also determined by the height from which light strikes the subject. Top light, which shines down from directly above the subject, can make deep shadows in eye sockets. It can also make landscapes seem more two-dimensional, since few shadows are visible. Most film lighting is done with the key lights angled about 40 degrees from the floor or slightly higher for the best modeling without casting excessive shadows. Under lighting, which lights from below the subject and casts shadows upward, occurs in nature infrequently and is sometimes used in films to lend a ghoulish look to faces.

    Much of the atmosphere of a lighting scheme is determined by the lighting contrast—that is, the relationship in light intensity between the brightly lit areas and the shadow areas in the frame. With great lighting contrast, there is a great difference in intensity between the bright areas and the deep shadows. With low lighting contrast (often achieved by using secondary lights to fill in the shadows), the lighting appears fairly flat and uniform throughout the frame. The degree of lighting contrast is often expressed numerically in terms of the lighting contrast ratio.

    A low-key lighting design has high lighting contrast and a Rembrandt-like look, with dark shadow areas predominating over light areas. Low-key lighting is associated with night, emotion, tension, tragedy and mystery. Film-noir films, as well as citizen Kane, are lit in moody low-key lighting, the dramatic look of the lighting being well suited to the black-and-white image. With high-key lighting, the lighting contrast is low and light tones predominate, making everything appears bright and cheery. High-key lighting is used for daytime scenes, comedy, straightforward material (like documentary interviews) and most studio television shows. Since high-key lighting has even distribution, it is useful for scenes where several cameras are shooting from different angles simultaneously or when an actor must be able to move freely without walking into areas of deep shadow.

    The terms high key and low key are sometimes confusing since the key light is actually lower in intensity relative to the fill light in high-key lighting designs. One means to distinguish the terms is to remember that actors in comedies are usually high-key personality types.