Noise transfer in screen-film subtraction radiography

The transfer of noise through the stages of a screen-film subtraction process was investigated. In particular the effect of measuring aperture size and film density on the measured noise granularity was studied. The relative contributions of quantum noise and film grain noise were found to depend on both aperture and density. Noise measurements are presented for a medium speed screen-film combination and also for a low noise alpha 16-Kodak Industrex C system. The effect of grain mottle and film blur on noise transfer through the multiple print process employed in subtraction radiography is demonstrated.