EXPOSURE COMPENSATION

This photo shows a normal exposure for a back-lit subject, highlights are well exposed but back-lit shadow areas are dark and without detail.

This photo was given one stop more exposure than the one above, that is (+1.0)

You have taken pictures of a snow scene and the prints from your shoot show snow that is gray in color instead of white snow like the original scene, you have taken pictures with the sun in the background your prints show a well exposed sun but objects in the foreground, grass, trees, buildings are shown as black silhouettes with no detail. In both instances you could correct the exposure using a photo editing program or you can make a in-camera adjustment before taking the picture.

This adjustment is done by opening the aperture one to two f-stops to compensate for that gray snow,dark foreground, opening the aperture supplies more light to the film or digital sensor, making the image brighter.
to make the image darker you would close the aperture one or two stops.

Most modern Digital Cameras have built in Exposure Compensation, if you want to make the image brighter by two stops you set the compensation display to ( +2.0 ) if you want to make the image darker by two stops you set the Compensation display to ( -2.0 ). Fill-flash is a good alternative to the above method of exposure.