During the serial shifting to an output buffer of the radiation induced charge signal accumulated in a row (or column) of an array, the successive signals are processed to improve the contrast of the sensed image. The portion of each signal of greater than a given amplitude is transmitted to a buffer stage and the remaining portion of each signal is removed. In one form of the invention, the signal-to-noise ratio is then enhanced at the expense of resolution by combining at the buffer the processed signal from a number of adjacent charge storage locations.