Adding A Third Or Fourth Light To Your Portrait Setup

Adding A Third or Fourth Light To Your Portrait Setup

by William Lulow

Okay, in the last article I spoke about the reasons for adding a second light to your lighting setup. Today, I will discuss how and why you would want to add a third or fourth light.

The reason for adding a second light is to increase the amount of information you show in a photograph. Portraits lit with only one light will have some definite shadows that will make the shot dramatic in nature. The way to open up those shadows and show more detail is to add a second light, a fill-in light.

Now, the reasons for adding a third or fourth light are many:

• To separate the subject from the background
• To add highlights to the subject
• To control the tone of the background
• To lighten the background
• To create other lighting effects

In most cases, you will need to lighten the background. The way to do this is to take one light and shine it on the background. Depending on the intensity of the light and the distance, the background can be rendered lighter or darker accordingly. This also goes for speedlights. You will remember that a speedlight mounted on the camera only throws light so far. It is usually not enough to light the background as well. Therefore, you need another light to make sure that the background is not black. A white background will be rendered various tones of gray if it is not lit separately. So, if you want a white background to show up as white, you need to light it.

Without lighting the background, you may want the subject to stand out, or be separated from the background. The way to do this is to take one or two lights, place them in the Edge light position and direct them toward the subject. This has the effect of lighting the subject from behind, placing highlights on the edges of the subject and separating the subject from the background with light. In order for this to work, these highlights must be brighter than the main light. If they are the same intensity, they will not show up as “accents.” The subject will have the same amount of light from each light source. As a rule of thumb, highlights or accents, must be at least ONE STOP brighter than the main light.

Now, the intensity of a light source various inversely as the square of  the distance between the light and the subject. The simple way of putting this is: if a light is moved twice the distance away from the subject, the effect of the light on the subject will be reduced by one-half. If the light is moved four times the distance, the effect will be one-fourth the intensity and so forth.

Conversely, moving the light half as close, will increase the intensity by a factor of two. The lesson is that the important factor is what is called “lamp-to-subject distance.” Especially when you use speedlights or studio strobes, this becomes critical to getting a proper exposure. Unless you have a light on the camera, it doesn’t matter where the camera is. The only thing that matters is how far the light is from the subject.

I’ve talked a bit about the reasons for adding more lights to a set, but here are a couple of examples.

This image was made by a main light to the left of the camera, a fill-in placed below the face and two lights aimed at the background to render it white.

This shot was made by a main light to the left of the camera, a fill-in to the right and a accent light to the rear, right of the camera. Here, the subject is separated a bit from the background by the accent light.

So, to sum up, a third or fourth light would be added to light the background or provide an accent light to separate the subject from the background or just to provide some added highlight to the portrait.