The Canon EOS Digital Rebel XS/1000D Companion

White Balance

While your Rebel XS is an incredibly sophisticated imaging instrument, it still pales in comparison to the human eye. Your eye has better autofocus, can perceive a much wider range of tones and colors, and has the amazing ability to autocorrect color under different types of light.

That last one may not sound that difficult, but think for a moment about your street corner. During the daytime, it's covered with sunshine (unless it's a cloudy day), but at night, it's lit up by a street light. The street light is very yellow, while sunshine is much "cooler"—closer to the blue end of the spectrum—and cloudy light cooler still.

Similarly, the light you're sitting in right now might be an entirely different color. It will vary if you're sitting under a fluorescent light or a tungsten light. Or maybe you have the book under a tungsten desk lamp, with fluorescent overhead lighting while sunshine streams through a nearby window.

Throughout all of this, your eyes still register the pages of this book as white. For the most part, no matter what light you move the book into, you'll still perceive the pages as white—they might be brighter or darker, but your sense of color will remain consistent, until the light level drops below a certain threshold, at which point your ability to perceive any color will be compromised.

We have yet to develop a technology that is as good as your eyes are when it comes to correctly rendering color under any type of light. Different types of film have ...