Effect of the number of grey levels on the detectability of a simple line signal in visual noise.

The number of grey levels, G, contained in a digitized image of an external event must affect the fidelity of reproduction of that event for physical reasons. The question arises as to whether there is a separate perceptual effect of G. Three experiments are described which investigate the effect of G on the visibility of a straight-line signal in visual noise using a signal detection analysis to separate the physical and perceptual effects of G. The results show that, for the type of displays employed, and for the specific task of detection of lines in visual noise, there was no effect of G on efficiency, which suggests that G had no separate perceptual effect.