Light Source: Lassoing Light

Imagine yourself standing in a magnificent setting, full of rich colors and textures. You want to be able to capture the image as faithfully as possible. When you get your video home you are disappointed to see that some shots look blue and lifeless. The colors are washed-out and the amazing scene is all but a memory. Unfortunately, when you shoot video with your camcorder, what you see is not always what you get. One of the biggest problems with video is that it does not render the colors your eye sees unless you carefully set the camera for the lighting in each specific shot.
In this column, we'll look at how to control the color of light by using colored gels. We'll also discuss color temperature and how to control it. Finally, we'll show you how you can use this knowledge to create beautiful video every time you shoot.

The Colors of Light

As you look out at the sky, you may see brilliant blues. Turning your gaze to the warm glow of a fire, you will see light with a yellow/orange tint. These differences are especially visible to the video camera. Technically, we call this color difference "color temperature" and measure it in degrees Kelvin (see Figure 1). In this case, temperature is not a measurement of heat, but a measurement of color. The temperature scale was devised by noting the color of pure carbon as it burns. At lower temperatures (3,200 degrees Kelvin) it burns with a yellowish/orange flame, as the temperature of the flame rises, it changes color from orange to yellow to green, then to blue and eventually white.
Different light sources have differences in color temperature. The sun is a very bright, hot light source that fills our world with a white/blue light. The color temperature for sunlight can range from 5,400 degrees Kelvin (5,400K) to over 12,000K, depending on the cloud cover and the time of day. The average color temperature for daylight is 5,600K. Incandescent lamps, like the ones in your living room, give off a yellow/orange light and have a color temperature that runs between 2,800K to around 3,400K with the average being 3,200K. Most camcorders have the ability to set their image capturing electronics to 3,200K (for shooting indoors) or 5,600K (for shooting outdoors). However, sometimes this is not enough. Just when you think it is safe to use your camcorder, you step into an office lit by fluorescent lamps and get green video. Why? Fluorescent lamps have a color temperature between 3,800K and 5,000K depending on the type of tube used. Unfortunately this is in the green range of the lighting spectrum and unless you are able to white balance your camera, your video will have a greenish tint. <…