black level 
The intensity of black in the television picture, frequently referred to as brightness; adjusted to compensate for ambient room light. Black level is set with a TV's brightness control using a PLUGE test pattern. Setting black level correctly is critical to overall picture quality, particularly the ability to see detail in dimly lit scenes of a movie. The term also refers to the ability of a display to produce an inky, deep black, which is often a problem in fixed-pixel displays.