The technique of three-point lighting has been used for years in both professional TV and photography studios.
It is based on the principles of chiaroscuro, but doesn't try to disguise the artificiality of the light. This method of lighting is simple but effective for many situations that call for lighting a particular subject or object. Three carefully placed directional lights—the key light, the fill light, and the backlight—can light a subject in a way that provides an appropriate level of base light for the video camera; gives sufficient shadow for definition of shape, size, and texture; and separates the subject from surrounding objects and the background. The three-point technique is appropriate in most ENG or EFP situations to satisfy basic lighting needs. Figure 1 displays a similar shot under three different lighting conditions.
Figure 2 (below) gives guidelines for light placement in a situation in which the subject is facing the camera.
As the name implies, the key light is the most important light and therefore is placed first. The key light should be the brightest and most directional. A key light placed on the camera-subject axis (right over the top of the camera) produces a very flat, shadowless picture. In most cases, this is not flattering to the subject.
Start with these guidelines for placing the key light:
• Place it anywhere from 10 to 90 degrees off the camera-subject axis, depending on the effect or look you are creating.
• For a subject not facing directly toward the camera, focus the key light on the opposite side of the subject's face from the camera position.
• Elevate the light above the subject at about a 45-degree angle from the camera-subject plane.
The key light creates a strong shadow, sometimes called the draw, on the subject's face. This is known as the modeling effect. The videographer is responsible for bringing the viewer's attention to the most important aspect(s) of the screen. Since the audience is naturally drawn to the brightest part of the screen, and since the key light illuminates an area brightly, the key light is used to focus the viewer's attention. When subjects are not looking directly into the camera, the key light should be the light that the subject faces toward, but not directly at—referred to as the short side of the face (eyes and mouth), it is lit by the key. Focusing the key light on the long side of your subject (the ear side) makes it seem like the subject is looking away from the light. This gives the appearance of subject discomfort or avoidance, which can be misleading, distracting, or unpleasant for the viewer. It also casts the draw, or shadow, out of view for the camera, thus losing the three-dimensional effect. For examples of the three point priniciple, see Figure 3 (below).
The next light to set when using the three-point lighting technique is the fill light, located at an angle about 10 to 45 degrees from the camera on the opposite side of the camera from the key. Again, the light should be placed above the subject to give a more normal appearance. In studio TV, the fill light is often a scoop or a Fresnel spot adjusted to give a wide or flooded-out beam. These types of lights are preferable because they are less harsh and soften shadows created by the key light without eliminating them. Unfortunately, portable kits rarely contain scoops or other diffused lights. Typically, portable kits have small spotlights without lenses. Since the key and fill lights are usually of equal strength in portable kits, the fill is often placed at a slightly greater distance from the subject, resulting in a less intense light for fill (remember the inverse square rule!).
Many portable kits have adjustable lights that allow the light to be pinned to a narrow beam to give sharp, bright light or flooded to give a softer, less bright light. For example, the fill light could be set at a distance from the subject equal to the key light and set in the flooded or wide position, and the key could be pinned. As a general rule, your key light should be twice as bright as your fill (a 2:1 ratio), but a key that is four times as bright as the fill (a 4:1 ratio) is not uncommon. The combination of properly set key and fill lights should give enough base light for the video camera to operate at an acceptable level and create a perception of depth, giving your subject a three-dimensional quality.
The third light in the three-point lighting technique is the backlight. The primary purpose of this light is to separate the subject from the background by highlighting or framing the subject with a rim of light. The backlight is most often a spot, both in the studio and in the field. It is focused on the back of the subject and aimed so it's not shining into the camera lens. Barndoors are very useful on backlights. The light is placed directly opposite the key light, behind and above the subject at an angle of about 45 degrees. It is not unusual for a backlight to be as strong as the key light for a key-fill-back ratio of 2:1:2. A more subtle 2:1:1 is the most common choice. Because the effect of a backlight as seen from the camera position is more reflection than illumination, the strength of the backlight must be considered in relationship to the subject or object being lit. A person with golden blond hair will reflect a great deal of the backlight toward the camera, so only a little is needed. A person with a lot of very black hair can absorb a great deal of light and may need a very strong beam from the backlight. There's a saying among cinematographers that a backlight should be felt and not seen. It is best to judge the strength of the backlight with your eyes and get the brightness just to the point where it is noticeable. See some guidelines for light placement in Figure 4.