1. In an electrophotographic copying method capable of producing copies of a magnification different than that of an original, including the steps of moving a uniformly-charged photosensitive member past an exposure station, moving an optical system relative the original to form a light image thereof at said exposure station to form an electrostatic latent image on said photosensitive member, varying the position and speed of said optical system relative the original for varying the magnification of the latent electrostatic image formed on the photosensitive member, and developing said electrostatic latent image by contacting it with developer in the presence of a developing electrode, the improvement including the step of varying the potential of said developing electrode in accordance with the magnification of said electrostatic latent image.