Contrast sense
Sense of contrast is the ability to perceive slight changes in luminance between regions which are not separated by definite borders. This is as important as to perceive sharp outlines of relatively small objects.
Contrast Sensitivity =
Lmax - Lmin
Lmax + Lmin
Note: Lmax is the maximum luminance and Lmin is the minimum luminance. Contrast sensitivity is reciprocal contrast at threshold. It is defined as the visual function measured using a range of sinusoidal grating pattern as the. visual stimuli. Various method to check for contrast sensitivity are Arden grating, Cambridge low contrast grating and Pelli Robson contrast sensitivity chart.