The possibility of locally increasing the gas-discharge light emission for a given photosensitivity of a planar GaAs semiconductor cathode has been studied. The maximum emittance of gas-discharge light for given values of the residual pressure, the feeding voltage and the intensity of external illumination is determined by the photosensitivity of the semiconductor cathode. In a system with inserted metallic current concentrators the local density of gas-discharge light exceeds the density of uniform gas-discharge light in the ionization system as many times as the working area of the semiconductor cathode exceeds the total area of the current concentrators. The filamentation was primarily due to the formation of a space charge of positive ions in the discharge gap which changed the discharge from the Townsend to the glow type. The assessment of the image formation is then based on analysis of the discharge light emission, visualized by taking a photograph through the transparent anode plate. Means of locally increasing the light emission and improving the working characteristics are proposed.