The human eye has a remarkable ability to adjust to different light conditions. Not only do our eyes have built-in auto-focus system and auto-exposure capability, but we also have automatic colour balance built into our brains. A white object will appear white to us whether viewed in sunlight or under overcast skies, or indoors under incandescent or fluorescent lighting that is because the human brain has the capability to compensate for such changes in perceived colour. A very efficient system indeed!

The digital camera's image sensor has the daunting task of emulating the human brain and therefore has to adjust colour so that the white appears white in all kinds of lighting conditions, be it fluorescent or tungsten indoors, on a cloudy day or in bright sunshine. Therefore ultimately it all boils down to "Colour Temperature" or what is generally known as "White Balance" in digital camera terminology."



Link: PC Review