Thursday, September 15, 2011

White Balance, Part 2: The Gray World Assumption and the Retinex Theory

WHITE BALANCE is one of the most important functions of digital color photography. Understanding a little bit of theory about this function could improve your photography.

Very many beginning photographers (and I was certainly one of them) are quite disappointed with the quality of their images. Although they may find it hard to put into words just what precisely is wrong with their images, bad color or a color cast may be a significant problem. When I learned about white balance and how to correct for it, I immediately thought that my photos looked much better.

Bad versus better white balance, among other things. Saint Vincent de Paul Chapel, in Shrewsbury, Missouri.

Clearly, the color of light is often variable, and the color my camera captures is usually somewhat different from what I see in real life. However, if I am careful to set the white balance, then typically my colors look much better under most circumstances.

There are some principles that we ought to keep in mind:
  • Our eyes do white balancing naturally. This leads to color constancy, where particular shades of color appear to be subjectively similar under a wide variety of objectively different lighting conditions.
  • White balance in photography corrects for extreme changes in the color of light; it is not a slight adjustment.
  • For the best results, we ought to do white balancing early in the photographic process.
  • We cannot rely on the camera or software automatic white balance function to give good results.