A method is provided for the real-time determination of signals to be summed from signals representative of an image portion which are respectively received from detectors belonging to the same optical sensor, the detectors being organized in a matrix formed by rows and columns, the signals to be summed being received on the same column. The method also determines the time during which the detectors must acquire the signals to be summed. The method determines a value representative of a modulation transfer function of at least one lens and/or at least one mirror placed upstream of the optical sensor, and a signal-to-noise ratio of the image portion, based on a location of one of the detectors and on a signal representative of an image portion obtained from the detectors. This representative value is dependent on the number. The method searches for the number and the time maximizing the representative value.