What we call aerial or atmospheric perspective is generally thought to have been developed by Leonardo da Vinci, although artists before him already knew the principal very well.
Important mostly for landscape drawing, it is based on the idea that there is an optical effect at work when we look at distant objects outdoors. Close to the Earth’s surface is a mix of dust and moisture that creates a kind of mist that sends light rebounding in all directions; this scattered light causes distant values to lose intensity, and therefore contrast. Therefore, in order to create an effect of depth in your landscape drawing, you need to make the objects close up have sharply defined outlines and a dark value. Distant objects, to the contrary, will need to be blurred and softened, and your values need to grade from the darks in the foreground to palest values at the horizon. Attention to this type of perspective will create a beautiful, mystical feel to your work.
If you decide to wander into the realm of color or water-soluble pencils, you will need to know the second principle of atmospheric perspective, after values: color.
Da Vinci noted that blue light penetrates the Earth’s atmospheric mist most easily, and indeed it is what gives us the impression that the sky is blue. It also serves to give objects in the distance a bluish look, which Leonardo observed and put to service in his paintings, to great effect.
Indeed, I remember that the master artist who taught me decorative painting – Vincent, the explosive Spaniard – gave us a rule about color that I was able to use to great advantage in my trompe l'oeil work.
He said to work our atmospheric perspective in terms of warm and cool colors as well; when working on a trompe l’oeil landscape, the objects in the foreground needed to be reddish-brown; the objects in the mid-ground needed to be greenish; and the ones in the far distance a cerulean blue. In later years I saw that this same principle played out in the work of great landscape painters like Lorrain, and learned that this technique is called “chromatic perspective”.
Vincent also taught us that the atmospheric mist made the sky paler near the horizon, and a deeper blue at its zenith. I subsequently saw this demonstrated in master paintings as well, and not only in Western art.
With a different color system, we can see these principles concerning the sky at work in this Japanese ukio-e by Hiroshige.
There is a similar use of values in Asian art as well, although it is taken further.
Literally the objects at the horizon vanish altogether, especially in certain Chinese paintings where distant mountains dissolve into almost nothingness at the horizon, and peaks are shown to be distant by disappearing into the empty upper reaches of pictorial space.