You are here

Intro to White Balance

Intro to White Balance

Why would we want to concentrate on white when we shoot in color? Because incandescent, fluorescent and sunlight differ a lot, proving that white isn't always white.

Why would we want to concentrate on white when we shoot in color? Because incandescent, fluorescent and sunlight differ a lot, proving that white isn't always white.

White is white, right? Well, yes and no. Take a white sheet of paper - it looks white. Look at it under a red light bulb, though, and it looks pink. You may not see red light bulbs every day in the course of your videography, but the light that you do interact with on a day-to-day basis has a very distinct impact on the colors your camera sees. In order for your camera to record colors accurately under different lighting sources, it needs to be white-balanced. Your brain white-balances automatically - you can walk from bright sunlight into a room lit by overhead fluorescent bulbs, and your brain automatically readjusts for the slight shift in coloring. If you're careful and pay attention, you may notice slight differences. Take a look around the room right now at different lighting sources, and see if whites look redder or bluer under different conditions. What colors do the light sources themselves seem to be?

It's All in the Balance

Fluorescent lighting, you may notice, puts a greenish cast on people, while tungsten light makes things look a little red. The people who built your camera know this, and physicists who study light have spent a lot of time trying to figure out exactly why things look the way they do. The color of light, for very complex reasons that you don't really need to know, is measured in degrees Kelvin and is referred to as color temperature. The color temperature of bright sunlight is about 6000K (six thousand degrees, Kelvin). Tungsten bulbs are considerably cooler at between 3000K and 3500K. Most of the other light that you will be working with exists somewhere in between.

By telling your camera what type of light you're working under, you can correct for types of light that don't look like sunlight and make your colors consistent from shot to shot, regardless of the light source. Without the proper balance, your colors will shift a bit and affect everything in your shot (e.g., skin tones, the color of water in a tropical scene, etc.), creating a less realistic look.

Your camera will most likely have a number of presets which are useful starting points. These have nearly universal icons for shade, sunlight, fluorescent and tungsten. There's also an automatic setting where your camera will make its best guess as to what the color balance ought to be. It's often good enough, but rarely exact.

Fluorescent's green shift is not as harsh as it once was, and you can now buy daylight-balanced fluorescent tubes, which means the lights emit nearly the same color as the sun. This is very helpful if you're shooting a scene with both interior light and sunlight - more on this later.

The Sun Is Always Right

One shade of light isn't actually any better than any other, but, since the sun is the light we know best and the one we've known since long before we had others to compare it to, every light is an imitation of sunlight. For that reason, sunlight is the temperature of light that we try to duplicate. On some other planet that's lit by a giant fluorescent tube millions of miles across, filmmakers may be trying to make their other lights look a bit green.

White Balance and Color Temperature

Here are the color temperatures that correspond to the various white-balance settings you'll find on your camera:

Auto: your camera's best guess
Sunlight: 6000K
Clouds: 6500K
Fluorescent: 5500-4000K
Incandescent: 3000-3500K
Temperature: you manually pick a temperature (in degrees Kelvin) that most closely approximates your light source (very useful with lighting sources that have a range of color temperature)
Pre/manual: you manually set the white balance by showing the camera a specific white or neutral grey surface

Will My Hair Look Better with Gel?

One thing you can do with mixed light sources is to gel some of them. This means you add a filter to the light to change its apparent color and balance it with your other light sources. If, for example, you're using tungsten floods to provide most of the illumination in a scene, but there are overhead fluorescent lights in the shot, you can put color correction gel over the fluorescents to make them match the incandescents, or you could gel your incandescents and make them look like the fluorescent lights. Then you set your white balance accordingly, and the camera sees everything the proper way: whites remain white and all color sources look white.

Setting a Manual White Balance

The exact steps for setting your white balance manually will vary from camcorder to camcorder, but it will always involve showing your camera a white or neutral grey card under the lighting that you'll be using (preferably a scene where your color temperatures match). If you watch the camera platform before a press conference, you may notice a cameraperson going up to the podium before the speaker arrives and holding up a grey card or a sheet of typing paper. This lets the cameraperson's colleagues zoom in on it and set their white balance properly.

While training the camera on the white card, set the exposure properly and fill the frame with white. Make sure to activate the manual white balance mode of your camera. Then you'll push the white balance set button and likely hold it for a second or two until you receive a message from the camera in the form of a word like good or possibly a flashing icon. Your white balance is set. Check your camera's documentation for the exact steps on setting white balance, and then try it in several different locations. Also try recording with an improperly-set white balance, so you can see examples of what happens if you're not careful.

Remember to reset your white balance every time you move from one lighting situation to another - especially when you are moving from outdoor to artificial light. Always do a manual white balance when you are working with mixed lighting (i.e., a scene with mixed color temperatures). If possible, gel the lights so that they're all the same color temperature. Companies like Porta Brace make white-balance cards on lanyards that you can connect to your camera's tripod. These cost about $5.

Don't forget to reset your white balance from manual when you leave a particular lighting setup. You don't want to discover the next afternoon that you've shot an hour's worth of video in sunlight with the white balance still set to fluorescent from the night before. I try to get in the habit of resetting my white balance to Auto when I shut my camera down. The Auto setting makes a guess that's rarely exactly right, but it's better than one that's completely wrong. The Auto function is often very confused by multiple light sources with very different temperatures.

Conclusion

While it's not necessary to remember the color temperature of tungsten bulbs as it compares to daylight, it's important to remember that the two are different and that they'll provide different lighting throughout the range of colors in your scene. Adjusting for these by using your white balance is critical to maintaining color continuity throughout your production.

Contributing Editor Kyle Cassidy is a visual artist who writes extensively about technology.

Tags:  September 2008
Kyle
Cassidy
Mon, 09/01/2008 - 12:00am