Color Calibration

Michael Hammond
October 2003

In video production, as in life, we often find ourselves concentrating on the big picture, only to miss the small details that can keep us from achieving our goal. One of these fundamental details is white balance. Despite advances in video editing software that allow us to 'fix it in post,' white balance remains an important component to understand early in the production process if we're to end up with the best possible video.

White balance in video production boils down to the concept of color temperature. Every source of light gives off a unique color temperature as seen by a video camera. We may not recognize these differences ourselves because our eyes and brain have an amazing capacity to make adjustments. For example, you see white as white in just about any setting, but your camcorder needs a bit of help. When you white balance a video camera, you're helping it adjust the ratios of all of the colors it sees against true white - the combination of all color - so that it records the truest possible color in a scene.

The scale used to measure color temperature is in degrees Kelvin. A light source with a higher color temperature - a higher Kelvin value - has more blue light than a light source with a lower color temperature - a lower Kelvin value. This means a cooler light has a higher color temperature. Confused? That's because this Kelvin scale runs counter to what we think of when we measure air temperature on a standard thermometer. Figure 1 shows the approximate Kelvin color temperature of some common light sources you may find yourself shooting with in video production.

If you're shooting outdoors in bright sunlight, the camcorder needs to adjust to that particular color temperature to represent the colors you see accurately on tape. If you then move indoors to shoot a new scene, the camera needs to readjust to the new light source and new color temperature. This process of adjusting is called white balancing and there are a number of ways to accomplish it.

Is it really a big deal if you mix up your white balance settings? In Figure 2, the image on the left shows what can happen if a camcorder recording indoors, with available ceiling and table lights, is white balanced for outdoor light. The camera will expect more blue light and less red so it will adjust itself to be more sensitive to blue. You end up with a reddish or yellowish image. If you set the camcorder with an indoor white balance setting but shoot outside in the bright sun, the camera will be more sensitive to the red light resulting in a heavily bluish image, as seen in the image on the right. It's clear that not being aware of your white balance setting can produce very disappointing results.

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