Sometimes a basic single color background is just boring. Adding some gels to the a background light makes it much more dramatic, even setting a particular mood or theme. Adding colored gels to your background light gives you a virtually unlimited number of backgrounds.
What you need
Start with a basic set of gels, such as the Strobist Gel Collection. I recommend it because it contains a large number of gels of different colors that are pre-cut to fit most flashes. Next, you need a method to attach the gels to your flash. I generally use the Lumiquest Gel Holder, or just some basic gaffers tape. As for the flash itself, you can do what I do and find cheap manual flashes online for as little as $50.
Don’t get hung up on the lighting. While a poor setup can cause light to spill on to the subject or wash out the color effect, you only need to know a few basics to avoid these problems. Ideally, you want 3 feet or more between the background and the subject to prevent spill. Angle the main lights enough to avoid spilling onto the background and washing it out. Some actual setups explain how it’s done.
In the first image, we saw just a plain black background using black seamless paper. The lighting was coming from a side angle to prevent hitting the background. In this image we have a single flash at half power with a purple gel shooting up from behind the subject. This is a very simple, yet effective setup since it used a single light source. To help the light spread out, the flash zoom was set to 24mm to make it as wide as possible.
Take it a step further by adding a second light with the same or a different color. In this case I changed the purple to a red and added a second flash with a blue gel. Notice that where the colors overlap, they actually mix and become purple. If you using two different colors, remember this mixing effect — you might have to take steps to flag the two flashes and keep the colors from mixing.
You can also use multiple gels on a single flash by covering half of the flash with one color and the other half with a different color. For a recent benefit shoot, I tried this with pretty decent results.
You see the distinct blue and red colors, but purple emerges where the colors mix. The colors mixed more than I liked, but the overall effect is visually interesting. I am going to continue to play with this technique to see what happens if I use a vertical card in between the two gels to separate the colors.
The following is an image from the shoot showing how the images turned out.
What I really wanted to achieve was a red, white and blue effect. Back in the studio, I experimented. The result is a three-light setup using bare flashes with the gels on the bottom and a non-gelled flash higher up to provide a white splash. If I used just a bare flash for the white, the spot was too big and washed out the other colors, so I added a Rouge 3-In-1 Grid to keep the light contained.
In the first test, the white spot was too small:
Photo credit: Kerry Garrison