Edge enhancement effect of vision on X-ray radiographs made using screen—film systems

Theoretical and experimental approaches for the edge enhancement effect of vision on X-ray radiographic images were carried out. Psychophysically enhanced portions in the density unit at both sides of a step edge image were derived from modulation transfer functions (MTFs) of vision and radiographic systems. Experimental values were obtained using a new method, in which a step edge image was compared with a standard film having continuous density change. Experimental values distributed around theoretical values and their qualitative behaviour were similar to those of theoretical values. Discrepancy between theoretical and experimental results was due to the non-linearity of the human visual system.