The brightness of a pixel. The value associated with a pixel representing it's lightness from black to white. Usually defined as a value from 0 to 255, with 0 being black and 255 being white.

A shade of gray assigned to a pixel. The shades are usually positive integer values taken from the gray-scale. In a 8-bit image a gray level can have a value from 0 to 255.

The brightness of a pixel in an image, expressed as an integer. Gray levels range from 0 (black) to 255 (white) for an 8-bit digital signal, and from 0 (black) to 4095 (white) for a 12-bit digital signal. Also referred to as gray value. See ADU.