Fortunately, the lack of lighting equipment doesn't prevent you from producing great results. Even though it might sound paradoxical (if not downright Zen), you must know how to work with lighting equipment to understand how to do without, since this allows you to optimize results by positioning your subjects or the available light for maximum effect.
So, I'll start there, examining the two most common lighting combinations used on location and in studios today. Then I'll discuss some lighting fundamentals to help arrive at a definition of "good lighting."
After all, you can't hit a target unless you know what it is.
Once we have a target, I'll discuss the tools available to help produce good lighting. One lovely characteristic of all video cameras is an absolutely egalitarian view of lighting. Cameras don't care whether you spent thousands of dollars on your lighting equipment, or mid-two figures, so long as the light is adequate and appropriately positioned. Accordingly, for those with $100 or so to spend, I'll describe how to buy highly effective lighting equipment at a fraction of the price of professional gear.
With all this as background, I'll describe how to apply what we've learned to common shooting situations you'll likely encounter in the field.
Three-point lighting has its roots in lighting as art rather than lighting as a necessary evil for the camera to do its work. The basic theory is this: Video is a two-dimensional medium served on a flat screen. Flat lighting, which lights each scene region equally, is visually uninteresting and serves only to emphasize video's two-dimensional nature.
To get around this, lighting should create "depth" within the video image and contrast between the foreground subject and the background. The basic tool for accomplishing both goals is three-point lighting, as shown in Figure 1.
As the name suggests, three-point lighting uses three lights. The key light is the primary light, and its job is to expose the shape of the subject, which it does by shining down on the subject from an angle and producing shadows, which is also often called modeling.
As shown in Figure 1, you position the key light approximately 45 degrees from the camera, pointing directly at the subject. The light should be above the subject, and shining down at an angle of about 45 degrees. A key light must be a "hard light" that produces shadows, but not so harsh that it creates excessive contrast between the lighted and the shadowed regions. More on hard and soft lights and lighting contrasts in the "Hard vs. Soft Lighting" section.
Positioning the key light is more art than science. In the key light image on the left of Figure 2, note the clearly visible shadow cast by the nose, which is also called the "nose caret." As a rule of thumb, the nose caret should never touch the lip (light too high) or protrude into the cheek area (light too far to the side).
Position the key light slightly higher to produce shadows that hide a double or triple chin, but make sure the eyes remain clearly visible. This is a problem for me (that's yours truly in the image) because my bushy eyebrows can block the light, making my eyes difficult to discern.
As you can see on the left in Figure 2, the key light did its job, producing a shadow that adds depth to the face. However, the contrast is a bit too strong between the lighted area on the right side of my face and the shadows on the left. To moderate this, we'll add a fill light to "fill" the shadows.
Where the effect of the key light is obvious, the fill light is subtler, softly reducing the shadows produced by the key light rather than announcing the presence of another light. To accomplish this, the intensity of the fill light must be less than the key light, an effect you can produce by using a softer light, a less powerful bulb, or by placing the light further from the subject.
As shown in Figure 1, the fill light should be placed at approximately the same angle as the key light, but on the other side of the camera. Placing the fill light at a different height from the key light will produce an asymmetry that enhances the desired modeling effect.
Compare the key light image in Figure 2 with the key and fill light image. You'll notice that the fill light did its job, softening the dark shadows produced by the key light and revealing some of the detail on the left side of my face.
The back light is placed behind and shines down upon the subject. Rather than provide true lighting for the scene, the back light should produce a subtle halo on the top and back of the subject that provides contrast to and visually separates the subject from the background, which enhances the three-dimensional appearance of the scene.
Ideally, you should place the back light directly opposite the camera, and it should have the same intensity as the key light. If it's impossible to place the light directly behind the subject, place it on the side and shine the light down on the subject, or place a light on each side, with both lights shining down onto the back of the subject. Be careful when positioning the light that it does not shine down on the camera lens, which can produce lens flares and even burn out pixels in the LCD viewfinder or panel.
If you look at the key, fill, and back light image in Figure 2, you'll notice that my hair and shoulders are lighted, providing contrast with the background. Though many television producers eschew three-point lighting for flat lighting, virtually all employ back lights to create this contrast.
So that's three-point lighting. So, what are the takeaways?
First, shadows are acceptable, if not desired. This is critical, because you can drive yourself crazy, especially out in the field, if you try to get rid of all facial shadows. Rather, it's important to place the lighting and the subject so that the shadows enhance, rather than disrupt the image.
Second, uneven lighting is acceptable, if not desired. Again, don't drive yourself nuts trying to get even lighting on each subject's face. Rather, it's critical to limit the contrast between the brightest and darkest regions in the video.
Third, back lights are essential to separate the subject from the background, especially (in my experience) with indoor shots.