One of the most important feature of a digital camera is the ability to change White Balance (WB) over different shots. As a user of film camera, when I moved on to digital, I was instantly taken by joy when I came to understand what WB was and how to use it while taking shots for a multitude of possibilities.

So then what is this WB? To understand WB better, let us first look at color of light. Not all sources of light are same and therefore not all lights are of same color. The color of light is expressed in Kelvin and Kelvin is unit of measure of heat or temperature. So when we say that the color of light is 2500 Kelvin we mean the color of light produced by a black body like carbon when heated to 2500 Kelvin. At lower Kelvin the light produced is warm in color towards red, orange, yellow and golden hue and as the Kelvin increases the color tends to get cooler, that is the color of light tends towards blue.

With this understanding, let us proceed further.

When we pick up a roll of film, we either take a Daylight or a Tungsten balanced film, as these are the only two options available. If we take a picture of a candle lit scene using a daylight balanced film, without flash and no filters, we get a very warm picture. This is so because the film in use was balanced for daylight. By daylight we mean a light at 5000K to 5500K. Take a daylight balanced film and shoot a heavily clouded scene once without any filter and again with a warming filter. The shot with the warming filter will appear more natural and the shot without the filter will appear with a bluish tinge. The reason for this is the color of light in a heavily clouded scene corresponds to around 7000K or even higher where as the film was balanced for 5500K. The use of a warming filter changed the color of light and brought it close to what the film was balanced for.

The way a digital camera produces an image is that it reads raw data from the sensor, applies the setting of the camera to the raw data and produces the final image. Among other things, the digital camera needs to know the color of light before it can produce the final image. The WB (White Balance) setting on the digital camera is used to convey the color of light. Most of the digital cameras have a auto WB setting in which the camera tries to detect the color of light by itself and some digital cameras allow for manual override of the WB.

Every time we take a picture, we tell the camera the color of light by means of either setting the WB at auto or setting the WB manually. Some digital cameras allows the WB to be set according to the most common source of light which corresponds broadly to bulb, tungsten, flash, sunlight, cloud and shadow, while other sophisticated cameras allow the user to set WB in terms of Kelvin.

This option of being able to set the WB for each shot enables the user of digital camera to do away with the cooling and warming filters. By simply setting the correct WB, the right color can be achieved. The use of cooling and warming filter were introduced mostly because there were only two types of balance available in film whereas in reality there were so many source and color of light. To deal with these, the filters were invented and used. Not anymore with digital.

Being able to set the WB as desired also exposes some creative possibilities. Setting the WB of the camera as higher than the actual color temperature will produce a warmer picture and vice versa.

As an example, look at this picture. This was taken on a cloudy day with the WB set to around 10000K where as the correct WB would have been somewhere around 6500K - 7000K.