X-ray beam detectors in one model can individually differ from one another. This can lead to differences in the amount of noise in an image recorded with the aid of the respective X-ray beam detector. In the present case, a variable is derived using an empty image, which variable reproduces the amount of noise, and this variable then determines the type and extent of a filtering process. Hence the image processing is adapted to the respective individual noise behavior of the respective X-ray beam detector. This is particularly suitable if the X-ray beam detector is a flat-panel detector (100) with a scintillator (22) and photodetector elements (12).