the invention relates to a method for the correction or compensation of individual differences between the conversion characteristics of the image sensors and the processing units of an x - ray detector which are connected thereto . it is assumed that a functional relationship in conformity with gw = f i ) exists between the quantity of radiation entering the detector and the grey value resulting therefrom for a pixel , where lij describes the approximately linear behavior of the sensor arrangement and fi the non - linear behavior of the processing unit . for the inverse value l ij − 1 a linear model function is used and for the inverse value f i − 1 a non - linear model function is used with parameters which can be calculated from calibration measurements with different radiation quantities . during later operation of the detector these model functions can be applied to the grey values obtained in order to correct said grey values with a high precision and in real time , the storage space then required being small as a result of the use of a single non - linear inverse value for each column .