Abstract: An embodiment of the device comprises: three subtracters, three multipliers and a correction coefficient determination device. The subtracters and multipliers make it possible to obtain three signals, whose values are multiplied by a same coefficient, in order that they retain the same ratios as the values of the signals supplied to the input of the device. The device for determining a correction coefficient comprises means for determining which of the input signals has the highest instantaneous value at each time, in order to apply thereto a predetermined, non-linear transformation and for supplying a correction signal which is applied to the multipliers.

Abstract: The correction consists in correcting the overall luminance, while retaining the original chromaticity of the analyzed picture. For this purpose, the device according to the invention comprises a correcting circuit receiving the color signals V.sub.e1, V.sub.e2 and V.sub.e3 and supplying corrected color signals, a matrixing circuit supplying the overall luminance signal V.sub.e, and a control circuit calculating eight transfer parameters defining the transfer function F, which transforms the signal V.sub.e into a signal F(V.sub.e) covering the scale of luminances in accordance with an equal distribution in order to satisfy the optimum vision conditions. The control circuit processes the signal (F(V.sub.e)/V.sub.e) and the correcting circuit supplies corrected color signals respectively corresponding to the products V.sub.e1 .multidot.(F(V.sub.e)/V.sub.e), V.sub.e2 .multidot.(F(V.sub.e)/V.sub.e) and V.sub.e3 .multidot.(F(V.sub.e)/V.sub.e).

Abstract: The device comprises a variable-characteristic nonlinear four-terminal network having one input for receiving a video signal V.sub.e and eight inputs for controlling transfer parameters. Statistical analysis of the amplitude of the signal V.sub.e permits acquisition of the luminance distribution function of said signal. On the basis of this distribution function, computing means determine the values of the transfer parameters to be applied to the control inputs of the four-terminal network in order to deliver at the output of the network a video signal V.sub.s which extends over the entire luminance scale and has the desired distribution for satisfying optimum conditions of vision.