Triangle lighting creates spectacular lighting for video interviews. Triangle lighting is just what the name implies, light from three sources pointed at one subject.
Triangle lighting takes a bit more work but the results are worth it. Next time you are watching any show that features lots of interviews, examine the lighting critically. Can you see the halo effect, evidence of a back light? How much difference is there between the bright side of the subject's face and the darker side? How deep is the nose shadow? Are the eyes lit clearly? Are glasses causing an annoying glare? Is there a splash of dappled light on the background? Triangle lighting is a common professional technique.
In triangle lighting, you have three light sources.
* Key light
* Fill light
* Back light
The key light should be the brightest of the three. As the name implies, it is your main light. The key light should be placed so it illuminated the majority of your subject's face, and this usually means having your camera fairly close to the key light. The key light should be off to the side of the subject's face about 30 degrees.
Your fill light should help do what the name fills, fill in the shadows created by your key light. Typically, you do not want to eliminate these shadows completely, you simply want to make them less dense so the key light should be less bright than your key light.
Your back light gives your subject what is called the "halo affect," a bright rim of light which outlines the head and highlights the hair. It is very flattering and helps your subject stand out from the background.
Setting your back light can be a bit tricky. You do not want it to create lots of weird shadows on the face so it needs to be reliably dim and focused directly on the back of the head.
Problems with back lighting include glare into your camera and unflattering shadows on your subject's face or shoulders. In order to avoid those problems, make sure the back light is placed enough to the side so it will not cause glare. To eliminate unwanted shadows, most back lights are fairly dim and readily heavily on barn doors. Barn doors are used to aim the light precisely where you want it and keep it off the places you do not. If you do not have barn doors, use aluminum foil. A special type of black foil is sold by professional lighting companies. It is not very expensive and works better than aluminum foil, but aluminum foil is functional. DO NOT use anything flammable, like newspapers.
Another gadget, called a snoot, works much like barn doors but in my opinion is better for back lights because it is easier to restrict your beam of light to your subject's hair. A snoot is a black, metallic shield shaped kind of like a cylinder. It has a narrow hole in the front. Placed over the light, a snoot restricts the beam to a small circular one. Snoots are great, but not very common.
Triangle lighting can be modified by adding a fourth light, called a background light. This light is just to brighten up your background and can help add a sense of depth to your shot.
Since a bright background is a no-no (it creates a silhouette) the background light should be fairly dim. When you are watching high quality documentaries, like what is on the History Channel, most interviews are shot with intricate background lighting. The background lights are often colored with color gels and templates are placed over the light to give a dappled effect. Color gels are nonflammable plastic sheets you place in front of your light. They are cheap, effective and come in all colors. Color gels are a great, inexpensive way for a low budget video to increase its professional appearance.
The templates placed in front of light to create a dappled pattern are often made from foil. Rip off a sheet of foil, poke some holes in it and there you go!
Triangle lighting and its variations are perfect for interviews. However, even in the professional world, not every interview rates triangle lighting. Often, interviews are done with only a key light. Sometimes a key and a fill will be used. Sometimes a key and a back light will be used. It is all acceptable and any added light on an interview always looks much better than just relying on natural light. My habit was to light interviews but try to shoot supporting video (b-roll) in natural light.