A question of (white) balance
- — 24 February, 2006 15:30
If you've bought a new camcorder, you've probably spent some time scrolling through the controls, pressing buttons to see what happens. And you probably came across one particular control that you didn't recognize: white balance. You may have wondered about this one. Why would you need to balance white? After all, white is white, isn't it?
Unfortunately, it isn't that simple. White balance is one of the trickier concepts to understand that you'll come across. It's why colors in your video -- and the still images your digital camera takes -- sometimes look funny. The color of objects depends on the color of the light that is reflected from them. This color can vary because different light sources (such as the sun, a florescent light, and an incandescent light bulb) produce very different colors. If you've ever taken pictures in daylight, then inside under florescent lights, you know what I mean: Indoor shots come out with an orange cast.
A clever British bloke figured this out in the 1900s and created a measure that can be used to describe the color that a light source produces: the Kelvin scale. On this scale, daylight is at 5000 Kelvins (usually abbreviated to 5000K) and an incandescent bulb is at 2800K. These different color temperatures are where the white balance settings on your camcorder come from.
So when you go from outdoors into a room lit by florescent bulbs, why don't you see different colors with your own eyes? Your brain receives the images your eyes see, ponders what color you are really looking at, and adjusts how you interpret that color. Of course (like most things to do with the brain) it's a bit more complex than that, but the gist is that your brain adapts for different light sources without your knowledge, which is a process called "chromatic adaptation."
But your camcorder or digital camera isn't as good at interpreting colors. Modern camcorders try to evaluate the colors they record, but their circuits aren't as clever as your neurons. So in videos, sometimes your Aunt Doris comes out looking green instead of the healthy shade of pink that she really is.
Setting the white balance
What can you do when this happens? Well, most camcorders default to a fully automatic white balance setting, in which the camcorder automatically adjusts the white balance. But you don't have to settle for this: Camcorders usually also provide a series of manual white balance settings for different light sources. You just pick the one that's closest to the light source and shoot away.
Most camcorders also have a mode that allows you to set the white balance yourself. To use this, find a flat area of white (such as a piece of blank paper) that is illuminated by the light source you're shooting in, zoom in with the camcorder to fill the screen with this white, and then use the camcorder's menu option to set the white balance. Many professional videographers carry around a white card for this purpose; you can buy white balance cards from most camcorder dealers.
It's also possible to use white balance to make people look better: If you set the white balance using a pale blue color, it makes skin tones look richer, rather like a light tan. The professionals call this "warm balancing" because it makes the colors look warmer; Vortex Media sells a set of cards for just this purpose.
You can also use the white balance creatively: Use your color printer to generate a page of various strong, bright colors, then use one of the colors to set the white balance as described above. I got the strange color effect in the image on the right by setting the white balance using an area of orange, not by sending my dogs to another world.