White Balance
As mentioned before, digital photos in RAW format enable you to change the white balance or color temperature after the fact. What does this actually mean? Well, every light source has a specific spectrum that affects the perception of colors which are exposed to this light source. In order to be able to describe this effect, a color temperature scale in degrees Kelvin was introduced. It corresponds to the color a so-called “black-body radiator” emits that is heated to this temperature. For example, daylight has a color temperature of 5,500 degrees Kelvin and incandescent light one of about 3,000 degrees Kelvin.
Photographers should ensure that their recording medium is appropriate for the current lighting in order to avoid color shifts. Formerly, one would have to buy different kinds of film and perhaps carry several cameras, although color filters could be used as well. Today, white balance can be adjusted on camera for each individual picture and changed again later. To give you a sense of the kinds of improvements this can yield, here is an example from the inside of the Frauenkirche which I captured two days ago:
