Illuminations: Why Three-Point Lighting?

Why are we always harping on three-point lighting? You know: key light, fill light and back light? Even when it's done well, it's a cliché and, when badly done, the result is as hokey as a yearbook portrait. Since it's widely used in theater, still and movie lighting, this venerable scheme must have something going for it, right? Of course it does, as we're about to see.

Like many other clichés, three-point lighting became widespread because it was so useful. The idea didn't start in photography, but in theater, where shadows on stage actors make their faces hard to see. Furthermore, shallow sets spread performers out into two-dimensional tableaux. Sound familiar?

To fix the first problem, lighting designers invented warm-side/cool-side lighting, placing yellowish gels over the lights aimed from one side and bluish gels on lights aimed from the other. Since our brains assume that direct lights are from either warm sun or light bulbs, they accept the warm-side lights as "light" and the cool-side lights as "shadow," even though a light meter may show little or no difference between the two sides. Together, warm and cool lights deliver facial modeling without sacrificing detail.

To counter the apparent lack of depth on stage, designers placed a third light above and behind the performers, to dust hair and shoulders with a rim of light. This accent separates the performer from the background and adds visual depth to the stage picture.

Voilá ! Just like that, three-point lighting was born.

When early still and movie photography appropriated theatrical lighting designs, they couldn't use warm (yellowish) and cool (bluish) lights effectively, since the film was black and white. Instead they varied the brightness, keying with a brighter light, filling with a less-bright opposing light and separating with a back light (also called a rim light or kicker).

In the real world, light can come from many sources at once, but in photography and videography, the illumination seems to come from a single source, whether natural or artificial. Surfaces turned toward that single source are light and surfaces turned away are dark.

Because camcorders can't see into shadows as well as our eyes can, even the dark side needs at least some light to prevent it from appearing black and featureless on the screen. We have to at least partially fill shadows to reveal details within them, while keeping them plausibly shadowy. So, with the key light acting as the main light source, the fill light opposite lightens the shadows.

Video images are even flatter than stage pictures, so the back light becomes even more important to separate the subject from the background and add a sense of depth. And there you have the classic three-point lighting setup, with the apparent light provided by the key light, contrast handled by the fill light and dimensionality accentuated with the back light.

By changing lighting instruments and placement techniques, you can vary the effect of three-point light to suit the overall style of your lighting design. To show you how, we'll demonstrate with each of the three most common lighting approaches: pictorial realism, realism, and naturalism.

Pictorial realism, which old-style Hollywood termed "painting with light," is a frankly theatrical style that achieves an impression of reality, although the lighting is actually quite artificial (think of classic movies like Casablanca). We'll start our tour here, because pictorial realism uses three-point lighting in its purest form.

First, the key light approximates the effect of an actual, real-world light source. You can key from either side of your subject, but let's place our light at 4:30 on an imaginary clock face (Figure 1). The light should be above the subject's eye level, aimed down as much as 30-degrees below the horizontal. This position creates distinct modeling for the eyebrows, nose, mouth and chin, especially with the spotlight typically used for this lighting style.

CAUTION: If you place the key light too far to the side, you may lose some of this modeling. If you raise it too high, on the other hand, you can exaggerate eye socket shadows and paint a Hitler moustache under the subject's nose.

Even a correctly placed key spot will throw dark shadows, so you literally fill them in with the fill light. A scoop (big round) or broad (wide rectangular) floodlight works well, especially when softened by spun glass diffusion. Position the fill at around 8:30 (to keep the shadow it throws out of the picture) and about at eye level (to soften the eye, chin and neck shadows).

Here's where pictorial realism reveals itself to the knowing eye. Move the fill light in and out, checking the effect on a reference monitor, until all facial details are clearly visible. When you achieve the perfect balance between retaining the shadows and revealing all the details within them, your videographer's eye will tell you that the effect is slightly overdone. But that's the idea: pictorial realism is not supposed to be truly realistic.

Now for the back light. Place it as close to 12:00 as possible without moving the stand into the frame. (This is not a concern if you can hang your lights overhead.) Place the light as far forward as it will go while remaining behind the subject. This placement increases the depth of the light splash on the head and shoulders, while keeping the light source from creating lens flare.