The distant mountains have a lighter value.

"Precisely! Distant objects look lighter for the same reason that they look bluer—the atmosphere between us and them. The more air, the greater the scattering of blue light.

"This effect also makes distant objects look soft or hazy—much less detailed than objects close at hand.

"Of course, artists observed this shift in color and value long before they could explain it scientifically. Renaissance artists learned how to create depth in landscape by imitating how our eyes see—this technique is called atmospheric or aerial perspective.

"Point to the places that demonstrate my use of atmospheric perspective in this painting of El Capitan in Yosemite Valley,

"I used color to create depth. The rich warm foreground looks quite close against the hazy cool background.

"Now what would you like to do?

"Talk about lighting the sky in landscape paintings?"

"Or are you ready to move on?"