Atmospheric perspective refers to the effect the atmosphere has on distant objects. Also known as aerial perspective, the atmosphere can affect many aspects of a painting or picture.
Contrast decreases considerably with distance due to this phenomenon. This means that there isn't a lot of difference between the lightest light color and the darkest dark. Saturation with distant objects also decreases with distance. However, brightness increases due to atmospheric perspective. As objects fade further into the background, they become brighter according to how much contrast is lost. Finally, atmospheric perspective may be weakened substantially with bright light. The lit area retains more of its original contrast and saturation. Emphasizing this area is one way artists can add drama or mood to a piece.