Suprathreshold gray scale is implied by thresholds.

Abstract

The inverse of the threshold just noticeable difference (i.e., 1/JND) is proportional to the slope (derivative with respect to visual stimulus luminance) of the suprathreshold gray scale at any stimulus and background luminances. Specifically, the inverse threshold and the gray-scale slope share 81% of their variance over six log units of target luminance; in log-log coordinates, 92% of their variance is shared. The strength of the connection improves when negative or positive contrasts are considered separately. Scientific literature is cited, empirical evidence is presented, results of theoretical calculations are discussed, and applications are described. For instance, suprathreshold gray-scale appearance is important in medical imaging, video rendering, industrial process displays, public information displays (e.g., at airports), military situation displays, heads-up displays, multispectral and other abstract scientific imaging, artistic lighting design (e.g., equal-appearing steps of gray scale), and color coding of text, image segments, or symbols for rapid reliable visual search.