A pure white object will have a different color cast when lit by different kinds of light (like my daughter's pacifier in the above photo lit by a tungsten night light). "White balance" allows you to correct for light of different color temperatures. Your camera will allow you to adjust the white balance of your camera in at least one of two ways: through your menu system or with buttons on the camera body. The latter approach is preferable--well, at least it's faster. In the list of available settings, there will probably be 4 types of options available to you:
- Auto White Balance. If you do not want to ever think about what your white balance setting is, you can set it to "auto white balance" (AWB) This setting will work pretty well most of the time. In fact, if you are shooting in RAW, you can do that all the time and set your white balance in the software you use. The only downside to this is that you're doing extra work after you load your photos.
- Settings Based on your Situation. You will probably see options like cloudy, shade, sunny, tungsten, fluorescent and flash. These options will not give you exactly the color temperature of your scene, but they will get you pretty close--close enough that you may only rarely feel the need to change it on your computer. If you remember to change your white balance setting as lighting conditions change, you'll be in pretty good shape.
- Custom. With this setting, you must take a picture of something with a neutral color (a pure white or grey card) in the same light as your subject. Then in the menu functions of your camera, there's a setting that tells the camera to use that photograph to calibrate the others. In other words, you're telling your camera, "This color is neutral grey/white. Correct the following photographs accordingly." This approach isn't usually very practical in the field. For one thing, you can't always get a neutral grey/white color in the same light as your subject without scaring it away. For another thing, lighting conditions outdoors change frequently, especially on partly cloudy days. I often use this setting indoors, but outdoors, I only really use it for macro photography.
- Kelvin. With this setting, you dial in the color temperature you want to use, in Kelvin. As you can imagine, this has little practical use in outdoor photography. It works when you know the color temperature of your lights.
Now you don't always have to correct for white balance if that's not what you want. I took the above photograph the day after Sept. 11, 2001. I was new to photography, but I was learning about exposure. I was watching the news about that horrible day, when the innocence of our nation was melting away. And as I went in to check on my daughter, her innocence struck me, particularly her peaceful look with a pacifier in her mouth. But the nightlight was lighting her face with such a red color, and to me, the color of her face contrasted with her peaceful look. She was going to grow up in a world that was much harsher than the one I grew up in. I had to capture that contrast in film.