At first glance the Levels adjustment is daunting, but it’s one of the most vital parts of Photoshop’s editing arsenal
In the Levels adjustment you can make adjustments to the image’s individual Channels, to target certain areas.
These icons are used to interactively set the black, grey and white points of an image.
These sliders adjust the available tonal range of the image. Pulling them inwards will remap the black and white points, fading the image.
A graph shows us how many pixels the image has for of the 256 luminosity levels in the visible spectrum. A well balanced image has a graph that peaks in centre and trails out evenly both ends.