White Balance
The adjustment that makes a neutral subject render as neutral, compensating for the colour of the light illuminating it.
Measured in
K and tint
In depth
Human vision adapts automatically to the colour of light, so a white shirt looks white under both a tungsten bulb and midday sun. A sensor makes no such adjustment, recording the actual colour of the reflected light. White balance applies channel multipliers that undo the illuminant's bias, and on a raw file it is purely metadata — changing it later costs nothing.
Examples in practice
A room lit by domestic bulbs records strongly orange until white balance is set to about 2800 K, at which point walls read white.