LIGHT OUTPUT

from a standard direct view TV is obtained by lighting up phosphors. If you want to produce something representing black, just don't turn on the phosphors in that area of the picture. Simple enough, right? Well no, it isn't actually that easy. If ambient light is hitting the surface of the set, the level of light required for a dark area of the picture will have to compete with that ambient light. The appearance of the "off state" of the phosphors is of course dependent on ambient light. If you were around in the early days of black and white TV you may remember that TV sets had a medium cream color when the set was off. The only way you could get a good black out of a B&W set was to keep all ambient light off the surface of the set. Black matrix picture tubes have been designed to assist with these problems in color TV's. Even black and white sets now have tinted glass fronts in order to reduce the effect of ambient light. This increases the apparent contrast of the picture. These changes in the surface condition of the set increase the apparent contrast when confronted with ambient light.