White Balance Defined

• Have you ever taken a picture inside without flash and the picture looked orange? That's because the image wasn't properly white balanced. When a photograph has correct white balance, all objects in the scene have a neutral color tone. That means white objects appear white, blues appear blue, greens appear green and grays appear gray. All cameras work to obtain a correct white balance regardless of lighting conditions. The science behind white balance starts with the color-temperature scale developed by physicist William Kelvin.
  
  

Degrees Kelvin

• The Kelvin scale measures the color temperature, or hue, of a specific light source. Daylight at sea level has an approximate color temperature of 5,500 to 6,500 degrees Kelvin. Under these daylight conditions, colors appear neutral. That is the goal of the white balance setting in a camera. When the color temperature goes below 5,500 degrees Kelvin, colors start to contain more orange and yellow. Incandescent light bulbs (household lights) have a color temperature around 3,200 to 3,400 degrees Kelvin. This lower color temperature results in an orange/yellow appearance on film. When the color temperature rises above 6,500 degrees Kelvin, colors appear more blue/purple. Photographs taken at high altitudes often exhibit this blue/purple colorcast. Flash units are balanced to simulate daylight and typically have a color temperature of 5,600 degrees Kelvin.
  
  

Automatic White Balance

• All digital cameras have an automatic white balance feature; some also have a manual white balance feature. Automatic white balance attempts to correctly balance a scene's color temperature regardless of the light sources available in the scene. For example, fluorescent lights have a color temperature that emits a green colorcast. Automatic white balance attempts to correct this green colorcast and make objects in the scene appear normal. Cameras with manual white balance options allow the photographer to manually adjust the camera's white balance settings in greater detail.
  
  

White Balance Challenges

• Automatic white balance does a great job most of the time, but certain conditions can fool the camera's built-in technology. Scenes that have multiple light sources of different color temperatures often fool the camera's white balance sensors. These scenes often require manual white balance adjustments. Another scenario that fools the camera occurs when a small subject is surrounded by a large expanse of color; for example, a child standing in front of a red barn. The large color expanse tricks the camera into making a white balance adjustment to offset the red barn. The resulting image contains too much cyan, the opposite color of red.