White Balance

White balance refers to the color tint of a photograph. Film and digital sensors are calibrated for certain types of light. Whenever an image is shot under different light conditions (or color temperature), white does not appear white. If an image appears reddish it is referred to as "warm", while bluish images are referred to as "cool". Images shot under fluorescent lighting that turn out green are usually just referred to as "icky", and accompanied by words I cannot repeat here.

Having a tint to photographs is not always a bad thing. Many photographers like to use warm images for landscapes and portraits. Cool color temperatures can make wonderful images as well. The trick is to make sure that color tinting in your images is deliberate. In order to use color tint to your advantage you should understand what light creates what tint. In studying color temperature we learned how light color is measured by its temperature. Now we need to see what light creates what temperatures/tints.

Light Sources and Approximate Color Tints
-Flame - Yellow to Orange
-Incandescent Lighting (your house lightbulbs) - Yellow
-Sunrise/Sunset - Orangish Red to Yellow
-Midday - White
-Flash - White
-Moonlight - Bluish to Faint Yellow
-Cloudy Sky - Bluish

In general, reddish color tints are more flattering to skintones than are bluish tints. Yellow tints can also tend to give a jaundiced appearance if they are too strong.

In order to control color tints, photographers use a few basic methods. Film photographers use specially calibrated film and/or filters to adjust white balance in their images. Digital photographers set the white balance controls in their camera based on the shooting situation. Some adjustment to color balance can also be made in a traditional darkroom or by using digital darkroom software such as Adobe Lightroom.


Source : http://photography.about.com