Digital cameras have given us many great things: the ability to preview your photos immediately and the ability to change the camera’s sensitivity (ISO setting) on the fly to name only two. But these digital marvels do come with a complex problem called white balance. Let me explain.
Light is the basis for all photography and without it cameras would have a hard time trapping images. Imagine trying to take a photograph in a totally dark room. A black picture would be kind of boring. Not all light is created equal though.
Noonday sunlight is somewhat “bluish” (though our eyes see it as normal-looking). Incandescent lights (light bulbs in your table lamp) are warmer, even orange/yellowish. Fluorescent lights are trickier still; they actually produce a greenish color.
Your brain does not realize these color-shifts though; those two marvelous little “cameras” in your head (your eyes) working with your brain adjust the color automatically and what you really see is normal looking light. Sometimes you can sense the difference though; like early evening when the sky is deep blue and the light from low-lying clouds glows orange.
In a digital camera the electronic sensor (the camera’s “brain”) is affected by these different tints of light and to compensate it is uses a sophisticated program called white balance. The sensor sees the tint of light (like when you take a snapshot of someone sitting next to a table lamp) and it senses the warmer colors and tries to adjust to compensate for the color shift.
When you are shooting pictures outdoors in the sunlight, the sensor sees bluer light and compensates by adding yellow. In florescent light the camera compensates by adding magenta colors to counteract the green light.
Most cameras allow you to adjust the white balance manually. Indoors and without flash, you can adjust the white balance for incandescent lights and your photos will come out of the printer looking normal. The setting on your camera might look like a light bulb symbol or it might even say “Tungsten.”
Which brings us to flashes. You may not realize it, but that pop-up flash on your camera is actually adjusted to produce light that mimics the color of sunlight (slightly bluish). That is why your photos look normal when you use a flash indoors under incandescent lights; the flash overpowers the light bulb and gives the photo a “normal” look. Your pictures might turn out “orangeish” if you didn’t use a flash.
The left photo above was taken with the white balance manually corrected for the incandescent lights above the table. The picture has a more or less “neutral” color shift and looks normal to the eye. The photo on the right has a warm glow and was not corrected.
In the “old days” when we all used a roll of film to take our pictures, we purchased primarily “daylight balanced” film. This film had a built-in white balance of 5200 degrees Kelvin (named for some smart guy who discovered the different colors of light on the light spectrum), which is a fancy way of saying it was white balanced for sunlight. Today, with digital cameras, we can change that setting on-the-fly.
Doing a “white-balance” procedure on your camera is really pretty easy. It varies somewhat by camera model, but essentially here’s what you do: with the “White-Balance” setting selected from your digital camera’s menu, point the camera at something white (like your Aunt Matilda’s white blouse or a table napkin at your best friend’s wedding reception) and press the shutter button. Voila! Your camera will “white-balance” for the lighting conditions you are under at that moment.
For example, let’s say you are inside a church banquet room for a wedding reception and all of the lights are fluorescent. Yuk! There is green light everywhere. Actually, your camera’s automatic white balance setting will do a pretty good job of color correcting all of that green light. But, if you are a perfectionist and want to make sure your photos are the best they can be, do a manual white balance.
It’s a bit complicated but once you figure out how color temperature works, you can do some cool things with it.
Blue toned pictured
So, what if you wanted to get creative and make a scene have a blue-tone. This blue toned picture might be great for low contrast situations and creates a moody blue glow around the person.
Here’s how to do it:
When you’re outdoors, set your white balance to tungsten lighting. This tricks the camera into thinking that the light coming at it is heavily orange. In return it adds more blue than necessary on top of the already blue daylight.
It’s a trick that used to take filters and special film or cross processing, and now you can do it with a couple buttons on the camera.
So, there you have it, the basics of light. Go experiment and have fun with your photography!
They say a picture is worth a thousand words, so look at the first photo on the left. This is a picture of my child bride, Lynda. In this picture, she is sharply focused, but so is the background trees and house. In fact, maybe the background is too sharp, clear and cluttered; almost to the point of being distracting. 
Depth of field is actually a term that describes a range of focus — or more accurately a range of distance measured in feet (or meters), of things that are still in focus in front of and behind what you are actually focusing on. That range of focus is controllable at the camera, but more about that in a moment.
The photos at the left are my own. They were taken in 1976 where my wife Lynda and I lived in Geneva, Switzerland. The one on the left is faded and turning pink. The one on the right was “fixed” with one click from some amazing software (see below).