Your digital camera uses math algorithms to evaluate the overall color characteristics of the vista it is about to record. If there is a color bias, the camera software attempts to neutralize it out. These algorithms work quite well most of the time but some scenes may be rendered with less than favorable colors. If they were perfect, a sunset would be rendered without that golden touch.

These color balancing algorithms attempt to mimic the human eye/brain involuntary color adaptation. It is worthwhile for you to observe this adaptation first hand as it provides insight into white balance. Procure some deep colored filters. You can use colored candy wrappers or holiday package cellophanes. Cut one, say deep red, and hold it over just one eye. Stare about at objects with this filtered eye. After a minute or so, remove the filter and look about. Quickly cover the left eye and then switch and cover the right eye. You will see that the once filtered eye now has an altered color balance. It’s bias is the complement of the filter. The eye that peered out with a red filter is now biased cyan. Don’t worry, this condition is only temporary. Try this again with a yellow filter, again with green. You are witnessing firsthand how the eye/brain accommodates different color illuminants.

Film cameras lack the ability to automatically white balance. For film photography, we applied filters to accomplish and or the photo lab applied color correction on a custom bases during the printing stage, making prints from color negative. Photofinishing printing machines sport complex color balancing algorithms that apply color bias corrections on the fly as each negative is scanned and printed.