The air around us is not totally transparent. When you look at something that far enough, a few hundred feet perhaps, you will see a kind of white haze, especially in a humid environment. If you look at faraway mountains, this becomes very apparent. You can use this in a painting or drawing by reducing contrasts for distant objects. The colors also appears "washed out". On Youtube: For all of you Mac lovers (.mp4): Click To Play And for the Windows followers: Click To Play