Step 1
First open the image for editing. The levels tool excels when used on photographs that are either over exposed (too light) or under exposed (too dark):
Step 2
In the layer window press the button that says: create new fill/adjustments layer. from there choose "levels" Alternatively you can open up the Levels Adjustment Tool from by pressing CTRL + L
Step 3
Now working with the three hash marks in the top portion of the tool.
Sliding the hash marks on the left will adjust blacks or darkness, and sliding the hash mark on the right will adjust the whites, or lightness of the image.
Result:
Here are side by side results:
You can use this great option for many things, but it's intended use was to correct over and under exposure problems with images and photographs, just always try to experiment with the settings. Good luck!
