In color representation, there are brightness and color nuances that are just perceptible. For this psychovisual evaluation, which is based on human perception and uses the smallest, just noticeable differences for evaluation, there is the evaluation quantity Just Noticeable Difference (JND).
JND is an evaluation quantity for the quality of displays and for video codecs and is specified in a JND index.
, the smallest noticeable difference, indicates the number of gray levels as a function of luminance
For video codecs, a JND is defined as the probability with which a viewer can detect differences between the original video and the decompressed video with 75% confidence. Higher JND values approach 100% at 4 JND.