From Ken Rockwell-
“Photos can look too orange, blue or green even if the subject looked OK to our naked eyes. Since we can preview the photos on our color LCDs setting white balance is easy.
Our eyes adjust this automatically just as they do for lightness and darkness. It would be great if cameras did this as well as our eyes do, but cameras often need a little help just like they do with exposure.
White balance settings may be altered for deliberate creative purposes, exactly as we do with exposure.
You can change the orangeness or bluishness of your images to make them as warm, neutral or cool as you want without having to use glass filters. You even can get rid of the green cast from fluorescent lighting, all without the glass filters we need for film. Cool, huh?
Setting the White Balance when needed is the key to great color photos. This comes out the same with an $5,000 camera or a camera phone. You need to adjust the White Balance at times with every camera. I’ve also found point-and-shoots to be better than the more expensive DSLRs at auto white balance!
Different kinds of light require different adjustments to give a good picture. If we consider full daylight as “normal,” then indoor incandescent screw-in light bulbs look orange by comparison and candle light looks almost red. Likewise, blue sky without the sun is very blue although when you’re in the shade everything looks OK to you and I. If you make a photo in the shade the picture comes out way too blue or cool looking.” (To read the rest of Ken Rockwell’s article, click here.)
I’ve been experimenting with the white balance settings on my Nikon D90 with interesting results. Last night I took photos of an old pencil sharpener:
The first photo was taken with no white balance corrections:
And this was shot under the same lighting, but I changed the white balance to a cooler setting. As you can see, the colors are now natural. One thing-remember to switch the setting for the next outdoor shot!