Used to indicate the amount and color of light being given off by an object and is based on the concept of a “black body.” A black body is one which absorbs all incident light rays and reflects none (therefore, a theoretical concept only). If the black body is heated, it begins to emit visible light rays, first dull red, then red, then through orange to “white heat.” It can be likened to the heating of metal. If a metal object is heated enough, the metal body will emit the array of colors mentioned above until the object achieves a bluish-white light. The amount of light being emitted by the body can then be correlated to the amount of “heat” it would take to get the body that hot and that heat can be expressed in terms of degrees Kelvin. Objects that give off light equivalent to daylight have a Kelvin temperature of about 6,500 degrees Kelvin. Colors with a bluish tint, have a color temperature of about 9,000 degrees Kelvin.