Different light sources give off different colors. For example, a tungsten light in your house gives off a yellow/orange color, while the sun at midday gives off a blue color. We usually don’t notice these differences because our eyes automatically adjust to the light source. When we step outside on a bright sunny day, our eyes adjust to the brightness and the color of sunlight automatically. A red shirt looks red to us whether we are indoors or outdoors — as long as there is enough base light to illuminate the shirt.
But unlike the human eye, a video camera does not automatically “see” colors accurately. Instead, we have to manually set the camera so it processes the colors accurately based on the dominant light source. This process is called white balance because we’re telling the camera to see a white object (white card or sheet of paper) as neutral white, with no other tint. If the camera sees white accurately, it will process all the other colors accurately.
A white balance test: Which one of the images below is correctly white balanced?
If you guessed the one on the right, you are correct! The image on the left has a blue color cast — the plaster behind the men looks blue-gray when it should have a sandy-brown-beige color. Notice also the poster on the wall (the one nearest the doorway): it looks sort of purple in the bad image and bright red in the correct one.
If we’re striving for accuracy in journalism, we need to make sure our images are as accurate as the facts in our story. In fact, your images convey factual information to the viewer, just as much (perhaps more so) than the words in your voice-overs and soundbites. Properly white balancing the camera is another part of doing good journalism!
Videographers and filmmakers measure the color produced by various light sources in degrees Kelvin. We refer to each light source as having a “color temperature.” It sounds like an odd concept, but it is very useful and important for you to know. The good folks at Createasphere produced this video, which helps explain things.