a signal processing method for analyzing an autoradiograph to identify the locations of radioactively labeled substances which have been resolved in a one - dimensional developing direction on a support medium is provided . according to this method , digital image data including a plurality of different levels and values obtained by placing the support medium and a radiographic film together in layers to record the autoradiograph of the radioactively labeled substances are subjected to digital signal processing to identify their positions in a manner which substantially eliminates background noise . a stimulable phosphor sheet can be used in place of the radiographic film to record the autoradiograph . the method described herein may be effectively used to identify selected components of various biopolymers .