White Balance Definition (photography): The color cast (tint) or color temperature of an image.
Understand that white balance is not all about white, but all colors. Yellow should appear yellow, pink show appear pink, and etc. There should be no color cast.
What is White Balance in Detail?
When we look at a white piece of paper, our eyes and brain are able to determine the color of paper is white under different light conditions such as cloudy or sunny weather; fluorescent, tungsten, or neon light, etc. This holds true for any object and its color. Our brain can determine the correct color of objects.
We know a lemon is yellow and a lime is green. Cameras do not know this. They have a harder time calibrating the white balance (or correct colors) of a photograph.
A camera is not as advanced as the human eye and brain, but still can do a pretty good job in automatically detecting the correct white balance. When the camera is not able to determine the correct white balance, then we have to manually adjust the camera’s white balance function to produce a desirable photo with the correct colors.
Alternatively, you can correct white balance in post-processing software such as Lightroom. To correct a photo’s white balance, you have to adjust the color temperature (which is the color characteristic of light measured in Kelvin).
There are times when correcting the white balance is not important or not required. Creative photography doesn’t always require a correct white balance. As stated many times, photography is subjective.
The below example is a bottle of Coca Cola photographed indoors under tungsten light, with a peachy color background. The photo on the left is without any white balance correction. The photo on the right has the white balance corrected. Pay close attention to the white letters on the bottles and notice the yellow color cast removed in the right photo.