Sometimes you may want to darken an image, either to correct a slight over-exposure or to deliberately produce a brooding low-key feel. This too can be achieved by altering the tone curve. Moving the highest point on the curve downwards will darken the whole image, but this will lose both shadow and mid-tone detail. This can be alleviated by moving the mid-point of the curve upwards slightly, flattening the upper part of the curve and brightening the mid-tones.
There is unfortunately no way to replicate this effect using the Curves function in Photoshop Elements. The closest approximation is to select the Darken Highlights pre-set, and then to move the sliders for Adjust Highlights, Midtone Brightness and Adjust Shadows to the left, while leaving the Midtone Contrast slider in its default position.