A PLUGE (picture line-up generation equipment) pattern is a test pattern used to calibrate the black level on a video display. Black level is the technical term for what we typically refer to as brightness. It determines the amount of light that a picture display emits for the darkest areas of an image.
PLUGE patterns vary in format, but all consist of lighter and darker areas of black (and sometimes white and/or gray) shades. A typical PLUGE pattern is made up of three dark vertical bars, each of which is called a PLUGE pulse. When the black level is too low, the bars register as: black, black, and dark gray. This level will make the colors in a display look washed out. When the black level is too high, all three bars appear black. This level will make the colors in a display look dark and drab. In either case, the colors surrounding the dark areas will lack vibrancy and will be less distinct than they should be. PLUGE patterns are included in most display calibration testing products.