Latent images which are formed on dielectric receptor sheets during exposure to object-modulated primary and stray X-rays, while the sheets dwell in the interelectrode gap of an ionography imaging chamber, are developed in an electrophoretic unit which neutralizes the effect of stray radiation upon the receptor sheets so that the developed visible images are reproductions of those portions of latent images which are formed as a result of exposure to primary radiation. The neutralizing involves ascertaining the intensity of stray radiation behind the imaging chamber by resorting to one or more dosimeters and one or more rasters or analogous devices which absorb stray radiation, and applying to the electrodes of the developing unit a reverse potential which is proportional to the intensity of stray radiation. Alternatively, the intensity of stray radiation can be ascertained empirically and the reverse potential is selected by hand, depending on the density and thickness of the object.