These two photographs reveal the difference between three different Kelvin temperatures. The image on the left was taken using daylight balanced film. The room is lighted with a 60 watt household bulb at dusk. The white walls have gone orange and the outside light is a deep blue. (Daylight film at 5500°K; tungsten light at about 2700°K; dusk well into 8,000°K.)

The second shot was adjusted using the equivalent of an 80C filter. Notice the dramatic "cooling-off" of the room. Not quite perfectly balanced, but much improved. And look at the color through the window. Yes, the world turns that blue at dusk! In fact, the French have a special name for that time of day, "Heure bleue," or "The Blue Hour."