A method is disclosed for automatically controlling the exposure in an X-ray imaging of a moving object to be irradiated. An embodiment of the method includes generating X-ray images at different times with a predeterminable pulse width of X-ray radiation; determining at least one moving image region from at least two of the generated X-ray images; determining at least one moving edge of the moving image region; selecting at least one pixel of the edge; determining the time dependence of the intensity of the pixel from the generated X-ray images; evaluating the time dependence of the intensity; and changing the pulse width in accordance with the evaluation. Alternatively, the spatial dependency of the intensity can also be evaluated close to the edge. Advantages of ensuring an optimum image quality and reducing negative influences of a sub-optimum parameter selection are realized.