Although light from the sun and a light bulb looks the same to us, they actually contain different mixtures of colors that affect the color of any scene they illuminate. The color of the light is specified by its color temperature in degrees Kelvin, somewhat like the room temperature is specified in degrees Fahrenheit or Centigrade. As color temperature increases it moves through the colors red, orange, yellow, white, and blue white in that order. Daylight contains proportionately more light toward the blue end of the spectrum. Incandescent light contains more toward the red end. (Despite the fact that blue light has a higher color temperature than red light, we refer to blue as colder and red as warmer). Here are the approximate color temperatures of lighting sources you are likely to encounter in the digital desktop studio.

• Incandescent—3,000° K
• Fluorescent—4,200° K
• Direct Sunlight— 5,200° K
• Flash—5,400° K
• Cloudy—6,000° K
• Shade—8,000° K

To capture images with colors that look like they were shot at midday, we can use flash, strobes, or bulbs with the same color temperature as daylight. Alternatively, we can take advantage of our digital camera's unique white balance system. This system adjusts the image so its colors appear the way they would look if shot in daylight. For example, the fluorescent setting compensates for the greenish light from fluorescent lamps and the tungsten setting compensates for the warmer, more reddish color of tungsten lights.

As you change the camera's white balance setting you can preview color balance by looking at a scene or captured image on the monitor. If you examine an image closely you may notice that white areas in particular have some color cast to them. If so, you may want to adjust white balance for subsequent shots. Many digital cameras offer a number of white balance settings, including the following.

• Auto works in a wide variety of lighting conditions and is the default setting that you should try first. If it doesn't work you can try other settings such as flash or tungsten, or manually set white balance if your camera lets you.
• Daylight is best when photographing outdoors in bright sunlight.
• Cloudy is best when photographing outdoors in cloudy or overcast conditions.
• Incandescent or tungsten is best when photographing indoors under incandescent lights.
• Fluorescent is best when photographing indoors under fluorescent lights. Often there is more than one fluorescent setting because there is more than one kind of fluorescent bulb.
• Flash is best when photographing with flash.
• Manual (also called "preset") lets you set white balance manually while aiming the camera at a piece of white paper, neutral gray paper, or other evenly lit neutral surface, under the same light you'll be using to take the picture. This is the best setting when photographing under mixed lighting (any combination of daylight, tungsten, and florescent), as you often are in the home or office.

Some cameras also have a feature called white balance bracketing that takes a series of three exposures. At least one is at the normal setting, one is redder, and the other bluer. Other cameras have a menu setting that lets you fine tune the selected white balance setting to make it slightly redder or bluer.

When lighting a scene, it's ideal if every light source has the same color temperature so the camera's white balance system can capture perfect colors. The problem is that there is usually ambient light pouring onto the setup from windows or other room lighting. On the part of the subject where you set white balance, there is a mix of this light. White balance is set for this mix, and it photographs beautifully. However, some areas of the subject, especially those in shadow areas or more distant from the lights, may be illuminated primarily by light from the window or other lights. These areas will not be properly color balanced-they will be contaminated by the ambient light. If skylight is the illumination, you'll see shadow areas that appear blue. One way to eliminate this problem is to block as much ambient light from the setup as you can, perhaps even photographing at night. The easiest solution however, is to choose bulbs that match the ambient light. For example, using 5000�K fluorescent bulbs with daylight coming in the windows will make the bulbs and ambient light close enough in color temperature that you won't get noticeable color contamination in shadow areas.