White Balance

If you come from the world of film, you may remember using filters to correct for incandescent or fluorescent lighting. Most people don't bother and their indoors pictures invariably come out with a yellow/orange or bluish cast. In the digital world, these correction filters are no longer necessary, replaced by a feature found in most -- even the entry-level -- digital cameras called, "White Balance."

Light Color Temperature

The reason that pictures turn out with a yellow/orange cast in incandescent (tungsten) lighting and bluish in fluorescent lighting is because light has a color temperature. A low color temperature shifts light toward the red; a high color temperature shifts light toward the blue. Different light sources emit light at different color temperatures, and thus the color cast.

By using an orange or blue filter, we absorb the orange and blue light to correct for the "imbalance" -- the net effect is a shift in the color temperature.

In digital photography, we can simply tell the image sensor to do that color shift for us. But how do we know in which direction of the color temperature to shift, and by how much?

Manual White Balance

This is where the concept of "White Balance" comes in. If we can tell the camera which object in the room is white and supposed to come out white in the picture, the camera can calculate the difference between the current color temperature of that object and the correct color temperature of a white object. And then shift all colors by that difference.

Most advanced digital cameras therefore provide the feature to manually set the white balance.

By pointing the camera at a white (or gray) card, filling the screen completely with it, then pressing the White Balance button (or set it in the menu), the camera does its WB calculation.

From then on, any picture taken will have its color temperature shifted appropriately. It's quite simple, really, and you should not be afraid to try it out and see your indoors pictures improve considerably (assuming there is enough light for correct exposure).

Preset White Balance

To help us in those special situations without having to go through the trouble of manually setting the white balance every time, cameras provide preset WB settings such as, Tungsten, Fluorescent, Cloudy, Sunny, etc. Using preset WB can improve on a picture, especially under indoors lighting.

White Balance
AWB	Preset WB = Tungsten

In the above example, the picture on the left is taken with the camera set to Auto WB. The indoor lighting is by two ordinary incandescent (tungsten) bulbs from the ceiling. It's not bad, but the fan should really be white. By dialing in a preset Tungsten WB, the image gives a truer representation of the scene.

Usually just selecting a Preset WB setting appropriate for the lighting situation is enough.

Auto White Balance

Since the days of the Kodak Brownie cameras, manufacturers have tried to automate everything for us. Hence, today's digital cameras also all sport an Auto White Balance (AWB) function. Depending on the camera brand, some AWB works better than others. On the whole, though, AWB works very well in sunny and cloudy outdoors, and fine for most indoors situations (a little orange or bluish cast does sometimes contribute to the mood of the picture anyway, e.g. the warm orangle glow of a candle).

Set your digital camera to AWB and take pictures under tungsten, fluorescent, and mixed lighting (i.e. tungsten or fluorescent, plus natural light coming through the window), and see if the results are OK. If they are, you can just use AWB.

Special Effects

Once you've selected a WB setting, just remember to reset this white balance setting when you head back outdoors into natural light, or you may end up with some strange, out of this world, colors.

In fact, by dialing in a WB setting inappropriate for the lighting situation allows us to create some special effects.

Let's say you are taking a picture outdoors and you want to make the light warmer, perhaps creating a late evening, sunset effect. To do that, we dial in a Fluorescent WB, in effect telling the camera that the light is too cool. The camera responds by shifting every color toward the warm, red values. Dial in a Tungsten WB, and the camera shifts all colors toward the cool, blue values. Lots of trial and error recommended here.

Summary

For most of us, Auto WB is fine and does a pretty good job in diverse situations, outdoors and indoors.

For those occasions when you are not happy with the color cast of your picture, choose one of the preset WB settings.

If this still does not give you what you want, consider manually setting the white balance by using a white card or sheet of paper (or white T-Shirt, etc.).

And, for ultimate control over white balance, consider shooting in RAW file format, and adjust in post-processing.