Method for characterizing the injection behaviour of an injection valve for liquids, having the following method steps: - injecting liquid through the injection valve into a measurement chamber, - radiating light into the measurement chamber onto liquid that is expelled by the injection valve in the form of a spray pattern, - detecting and scanning temporally successive spray images produced by light that is reflected at phase boundaries of the spray pattern expelled by the injection valve and that is imaged onto a recording device (12, 22), in order to obtain spatially resolved intensity distributions, - evaluating the intensity distributions assigned in each case to the detected and scanned spray images, wherein such image matrix elements containing image information assigned to the imaged spray pattern are identified in the respective intensity distributions and a measure of the injection behaviour is ascertained on the basis of the respectively identified image matrix elements and their time evolution, characterized in that a relative injection rate that serves as a characteristic variable is ascertained, as a measure of the injection behaviour, on the basis of the following relationship n t = ∑ j = 1 m I P j t ≥ G ∗ K j I P j t ∑ j = 1 m K j I P j t wherein n(t) denotes the relative injection rate in functional dependence on the time t, G denotes a limit value between high and, by comparison, significantly lower intensity values, P j denotes a j-th image matrix element of a respective spray image detected and scanned by the recording device, j denotes a summation index extending from 1 to m, and K j denotes a respective correlation factor, wherein K j takes into account a light intensity information value I captured in the respectively assigned image matrix element, wherein only such image matrix elements P j having light intensity values that are greater than the limit value G or are equal to the limit value G are taken into account in the summation in order to identify image matrix elements assigned to the spray pattern contained in the respective spray image. - injecting liquid through the injection valve into a measurement chamber, - radiating light into the measurement chamber onto liquid that is expelled by the injection valve in the form of a spray pattern, - detecting and scanning temporally successive spray images produced by light that is reflected at phase boundaries of the spray pattern expelled by the injection valve and that is imaged onto a recording device (12, 22), in order to obtain spatially resolved intensity distributions, - evaluating the intensity distributions assigned in each case to the detected and scanned spray images, wherein such image matrix elements containing image information assigned to the imaged spray pattern are identified in the respective intensity distributions and a measure of the injection behaviour is ascertained on the basis of the respectively identified image matrix elements and their time evolution, characterized in that a relative injection rate that serves as a characteristic variable is ascertained, as a measure of the injection behaviour, on the basis of the following relationship n t = ∑ j = 1 m I P j t ≥ G ∗ K j I P j t ∑ j = 1 m K j I P j t wherein n(t) denotes the relative injection rate in functional dependence on the time t, G denotes a limit value between high and, by comparison, significantly lower intensity values, P j denotes a j-th image matrix element of a respective spray image detected and scanned by the recording device, j denotes a summation index extending from 1 to m, and K j denotes a respective correlation factor, wherein K j takes into account a light intensity information value I captured in the respectively assigned image matrix element, wherein only such image matrix elements P j having light intensity values that are greater than the limit value G or are equal to the limit value G are taken into account in the summation in order to identify image matrix elements assigned to the spray pattern contained in the respective spray image.