Getting familiar with Photoshop tools

The levels tool can move and stretch brightness levels in a histogram using three main components: a black point, white point and midtone slider. 


Adjusting the black and white point levels


When considering adjusting the black and white point levels of your histogram, ask yourself: is there any region in the image which should be completely black or white, and does the image histogram show this?


NB: Holding down the "ALT" key while dragging the black or white point slider is a trick which can help avoid shadow or highlight clipping, respectively.  

Adjusting the midtone level

Moving the midtones slider compresses or stretches the tones to the left or right of the slider, depending on whicbrighten or darken the midtones wh direction it is moved. Therefore, the midtone slider's main use is to ithin an image.

Information gathered from: Using the Photoshop levels