Why the light from many discharge lamps makes red things look dull?
Mercury lamps, most metal halide lamps, most sodium lamps, and “cool white”, “white”, and “warm white” fluorescent lamps have a shortage of red and green light in their spectral output. These lamps also have a surplus of yellow and/or orange-yellow. Since red plus green looks yellow, taking away red and green and adding yellow do not affect how the lamp’s color looks. Nearly all yellow objects reflect red, orange, yellow, and green. Increasing yellow output and decreasing red and green does not change how yellow objects look. However, red objects generally reflect mostly just red light. With the shortage of red light, these look darker. If they are not pure red in color, they will not only look darker but also less red in color. Unphosphored (clear bulb) high pressure mercury lamps are especially bad at this, since they make very nearly no red light at all. This is not a problem with most compact fluorescent lamps, most 1-inch diameter 4-foot lamps, and other fluorescent lamps that hav
