GRADATION CORRECTOR WITH IMPROVED SMOOTHING, SIGNAL-TO-NOISE RATIO AND FAST RESPONSE TIME

In a gradation corrector used in a television receiver, a clipping circuit is connected to an output of a histogram memory and a clipping level of the clipping circuit is changed in accordance with an output of an S/N detecting circuit. Thereby, when the minimum value is detected, it is possible to prevent a large variation of the value to be detected which may be caused from noises or the like. Also, a circuit for detecting a change in video scene and a recursive filter circuit composed of an adder and a xK circuit (and a two-input/one-output selector circuit are provided on the output side of a clipping circuit and the coefficient value K of the xK circuit (or the selector circuit is controlled in accordance with an output of the video scene change detecting circuit. Thereby, it is possible to make a smooth gradation correction which is not affected by noises or the like (or to make a gradation correction with rapid response which follows a change in video scene.