Abstract: A method of coloring a black and white video signal is provided. At least one area of a frame is defined with reference to luminance values in that frame, and luminance levels are assigned to that area. A color is then assigned to that area, and the area is colored with it. In a subsequent frame, luminance levels are used to determine which part of the preceeding frame has been carried over into the subsequent frame and which portions of the subsequent frame adjacent that part have the same luminance values. That part and those portions are then colored with the respective assigned color.

Abstract: A method of modifying luminance levels of a black and white video signal is provided. The signal is fed to a voltage controlled amplifier and to first and second clipper amplifiers. Each clipper amplifier has an adjustable gain and an adjustable clip level, which are set to desired levels. The outputs of the clipper amplifiers are fed to a summation amplifier in which they are summed to produce a control signal. The control signal is fed to the voltage controlled amplifier, to vary its gain, and thus to compress one band of luminance levels whilst expanding another band of luminance levels.