Adjusting the light levels may not be enough to even out all the darks and lights in a picture. To further correct the picture, you can adjust the shadows and highlights.

Adjusting midtone contrast will increase or decrease the difference between darks and lights in your photo. You can see in the first image that there is a greater difference between the two than before adjusting the midtone contrast.

Darkening highlights is useful for darkening particularly light spots in a picture without having to select that specific area.

The Lighten Shadows tool is used for lightening particularly dark spots. Spots that contain detail (like the Nikon logo over the lens) may appear solid black; lightening shadows can bring out the detail. Use this tool only in small doses, though, as black objects are usually considered "shadows" in a program, and they will be lightened as well. Overuse of this function can also result in grainy spots.