Histogram

A graph that depicts the distribution of pixel values across the tonal range, and the relative number of times each tone is recorded. Digital cameras and scanners assign brightness, contrast, and black or RGB (red Green, Blue) colour values to each image pixel. A pure white is represented with a value of 0 (levels of colour); A PURE BLACK EQUALS 255. Inspecting the histogram of a digital image is a good way to quickly evaluate the tonal range quality and highlight and shadow details.