Lighting The Background

Lighting The Background

by William Lulow

I have written a lot about the background light in past blog articles, but when you are shooting in the studio, or even on location with flash, the background needs to be lit separately from the main subject if you wish details to be seen. If you remember that the flash only goes so far and when you are using a flash-on-camera setup, say, it really is only strong enough to light your main subject. One of the reasons for this is that many speedlights, like the ones you would mount on your camera’s hot shoe, are programmed to emit just the amount of light necessary to ensure a proper exposure of the subject directly in front of it. It won’t be enough to light the background as well.

If you think about “lamp-to-subject distance” as one of the main principles of lighting, you can understand why you need to think of the background as a separate “subject” from your main one. Therefore, if you wish to show details in your background, whatever it is, you have to think about lighting it.

One example of this is that when you use a flash-on-camera, the subject will be lit, but the background will be black. Here’s an example of what I mean:

This was a typical flash-on-camera “grab” shot where I didn’t really have time to light the background, so you can see that it came out dead black!

This example, on the other hand, is one where I purposely put some light on the background. As a matter of fact, there was no light on the camera at all:

This image was shot at the same party, in the same backyard. This time I added two extra flash units to throw some light on the table in the rear of the photograph to give more of a “party feeling” to the shot.

Here are another two images – one with the background lit and one without background lights:

This fashion image of a black dress, needed a light background to make it stand out. Two lights were placed behind the model and to either side (behind the walls) and lit up the background. This next shot of a light colored dress needed to be on a dark background, so all I did was to turn off the background lights:

The location was the same, just the lighting was different.

Another example is, you might think that if you placed a subject against a white background and then set up an umbrella or other light to light it, that the subject and background would both be lit. In reality, the subject might receive the right amount of light, but the background would reproduce a shade of gray, not white. The reason for this is that the light from the flash “falls off” as the distance to the background increases. So, if you want to render a white background as white, you must light it separately from the subject.

Here’s another example of what I mean:

Here is a studio setup I did for some corporate portraits, some of which had to be full-length shots. If you look closely, you can see my background lights behind to the two black shades on either side of the no-seam. If they weren’t there, the umbrella and softbox would not have provided enough light for the background and, given the length of no-seam I needed, the background would probably have actually been BLACK!

This image was made with my iPhone with just the room light. You can already notice that the background is going gray.

Here’s an example of one of the images from this shoot:

Notice the difference in background tone! This one is really pure white. In order to reproduce the background as white, you need to make sure that it is at least one f/stop more than your main light.

A few years ago, I was playing around with the concept of actually flooding the background with light. As a matter of fact, I wanted to light the background so much that the light would actually spill over on the subject. I saw that it began to produce an interesting kind of “flare.” I decided to see if I could exploit that flare for dramatic effect. These images were made with the background lights set at two to three stops greater than the main light. Both images were lit with two lights on the background and a large umbrella for a main light.

They were also then filtered with a haze filter over the lens that increased the effect of the flare.

The take-away here is that in order to control the tone of your background it has to be lit separately from your subject. If you treat your background as a subject in itself, you can readily see how to reproduce it just about any tone you wish!