The Levels tool in Photoshop adjusts the brightness of an image at three points: black, white, and midtones. It is great for brightening up dull images.
This example image is dark and lifeless. We will use the levels tool to brighten it up.
1. Make sure your layers palette is in view. Go to Window > Layers (or press F7).
2. Open your image. You layers palette should should one layer (your photo).
3. Click on the adjustment layer icon (the black and white circle) and choose LEVELS.
4. A Levels dialogue box will appear that looks like this
5. Don’t be intimidated by the box…the levels represent the color points in your image. The goal of a photo is to have the “curve” of colors extend all the to the blacks (the left) and all the way to the whites (right) with a peak in the center (midtones). That would create a photo with the full color range. However, if your photo doesn’t do that you can “help” it.
Our example photo is missing colors in the white (light) areas.
6. In order to fix that, we are going to drag the white slider to the point that it meets the “black mountain.”
7. In one quick and easy step your photo will improve dramatically.