Above is an example of an original Nikon Coolpix image straight from the camera.
A good starting point with the levels command is to click on your Auto button, which often gives amazingly good results. In this case however, it gave a colour cast. With the palette still on screen press the Alt key and the Cancel button changes to become a Reset button.
The level palette below shows a histogram, this is a plan of our image showing the darker pixels on the left-hand side with the light pixels to the right-hand side. In the center are the mid tones.
You can see from the levels palette shown below that some of our lighter pixels are missing.
By moving the slider to the left we can fill in this gap. Click OK once you are happy with your adjustment. If you now reopen the levels palette as we have done below you can see that you now have a full range of pixels.
Place your cursor over the image below to see what a difference levels can make.
More Tutorials: 
