How to Apply One-Step Auto Fixes in Photoshop Elements 11
The Auto Levels command adjusts the overall contrast of an image. This command works best on images that have pretty good contrast (detail in the shadow, highlight, and midtone areas) to begin with and just need a little adjustment, but it can also work wonders for seemingly unsalvageable images.
Auto Levels works by mapping, or converting, the lightest and darkest pixels in your image to black and white, which makes highlights appear lighter and shadows appear darker.
Although Auto Levels can improve your contrast, it may also produce an unwanted colorcast (a slight trace of color). If a colorcast happens, undo the command and try the Auto Contrast command instead.