In a method for adjusting the overall luminosity of at least a part of a matrix screen, each row of the part is processed several times non-periodically to display half-tones. Each processing consists of a semi-selective operation followed by a selective operation. A delay is planned between the selective operation and the semi-selective operation, this delay being proportional to a weighting factor that is adjustable as a function of the desired overall luminosity and proportional to the time interval between the beginning of the treatment in progress and the beginning of the next treatment.