The most basic setup for lighting human subjects is Three-Point Lighting. This setup consists of three lights; key, fill, and back lights (See figure 9.6.1). There is no rule for what kind of lights or lamps are used in this setup. In fact, when shooting outside, you might use the sun as one of the lights and a reflector as another.
The Key Light is the primary source of illumination for your subject. It is typically placed at a 45-degree angle from your camera. This allows the light to show the subject’s shape and may cause shadows on the opposite side of their body.
The Fill Light is meant to control the shadows caused by the key light. This does not mean shadows need to be eliminated entirely, but you can control the contrast between the two sides of their body. The fill is placed at a 45-degree angle from the camera on the opposite of the key light. You can check the contrast of the key and fill using an incident light meter.
The Contrast Ratio (sometimes called a Lighting Ratio) is the difference in brightness between your key light and your fill light. Your key light will be the brightest light and you can control how bright the fill light is to create whatever ratio is needed for your production. You can measure the difference between the two lights using an incident light meter. When you set the ISO and shutter speed, the light meter will tell you what f-stop is needed on your camera for that light.
For example, if we were lighting a subject with the key light bright enough to require f/5.6 on our incident light meter, we could then adjust the fill light to be equally as bright or dimmer than the key light to create contrast and shape (See figure 9.6.2). When the light meter reads that we need f/4.0 for our fill and f/5.6 for our key (1 f-stop difference), we know the fill light is half as bright as the key light. When the fill light is at f/2.8 and the key is at f/5.6 (2 f-stops difference), we know the fill is 1/4 as bright as the key light. Depending on the look you want, you can adjust your contrast ratio to fit that style.
The video below will demonstrate what different contrast ratios look like and how to create them.
The Back Light, sometimes called a hair light, is used to visually separate the subject from their background. It illuminates the top of the head and shoulders, which creates separation from the background. The back light is placed behind the subject (See figure 9.6.3), but if the light stand is in your shot, you can place it on the opposite side of the key or fill lights.
Other Light Designs
Although three-point lighting is the standard for lighting, this does not account for lighting anything other than the subject. To light the background, you will use a background light or lights. The only guideline for lighting your background is to make sure the light cannot be seen on camera. If you are conducting an interview, it is pleasing to the eye to have even lighting in the background, meaning there is no hot spot or an area with harsh shadows. Everything in the background is lit at a similar intensity. You can check the evenness of the light with an incident light meter.
Beyond the background, you can choose to use any number of lighting setups that will create a different effect on how your subject appears on camera. Figures 9.6.4, 9.6.5, 9.6.6, and 9.6.7 demonstrate different lighting setups for portraits.