1. A method for improving contrast in television pictures and other natural picture sequences provided in a selected chronological sequence of successive pictures, comprising the steps of: gathering pictures of the picture sequence into histograms, processing histogram class values of the gathered histograms by equalizing histogram class peaks, temporally filtering the processed histograms to prevent flicker, forming mapping functions on the basis of the processed histograms either before or after said step of filtering, and altering said histogram class values of the pictures in the picture sequences on the basis of the mapping functions, said method being characterized in that the step of processing includes the steps of: cutting off values from histogram classes surpassing a given predetermined limit, redistributing the cut-off values in the histogram according to a distribution weighted toward the classes lying near to said classes surpassing said limit, and wherein said step of temporally filtering is carried out by an adaptive edge-preserving filter structure.