A normally opaque recording sheet that can be converted by spark erosion into an image of an original that has low background in areas corresponding to black areas of the original. It comprises an optically transmissive insulating carrier sheet, an opaque layer of aluminium, chromium or nickel deposited on the carrier sheet which layer is from 0.025 to 1 micron thick and has a surface resistance of from 2 to 0.5 ohms per square, and an insoluble opaque spark-erodible protective layer comprising electrically conductive particles dispersed in a resin and coated onto the aluminium layer in an amount of from 3 to 18 g.s.m. Both the protective layer and the over-layer can be eroded away by passing electrical current between the recording sheet and a moving electrical stylus. The resulting positive or negative imaged recording sheet can be employed in transmission either to produce film intermediate positives or negatives, or by contact with pre-sensitised offset litho plates to produce long run lithographic plates. The opaque over layer and the opaque image area both remain in non-image areas and are both present in imaged areas so that a low background is achieved.