How to Read a Histogram in Photoshop

A histogram in Photoshop is a type of bar graph. Histograms are displayed in the Levels dialog box, the Histogram palette, and can now even be displayed in the Curves dialog box. A histogram for traditional 8-bit images contains 256 bars that vary in width and height to show the distribution of colors or tonal information in an image. Each bar represents one brightness value from black (on the far left) to white (on the far right). The height of each bar represents the number of pixels that correspond to that brightness value. The histogram helps you “see into” the image and locate where the darkest colors begin in each color channel and where the lightest colors end.