1. In an electronradiography system, the combination of: an imaging chamber having first and second spacedelectrodes with a gap therebetween and means for positioning a dielectric receptor sheet in the gap at one of said electrodes during an exposure for producing a latent electrostatic image on said sheet with a relatively high charge density in the background area and a relatively low charge density in the picture area; a charge neutralizing unit having a corona generating unit, a bias conductor, means for positioning said receptor sheet with latent electrostatic charge between said corona unit and bias conductor with the surface of said sheet carrying said charge facing and spaced from said corona unit, and means for connecting a bias voltage source between said corona unit and bias conductor, so that the magnitude of said relatively high charge density is reduced without reducing the magnitude of said relatively low charge density; and a developer unit for receiving said receptor sheet with reduced charge density and developing said latent electrostatic image into a visual image.