Saturday, December 28, 2013

Perceiving Sky

Ram's Head
Georgia O'Keeffe, 1935
Painting landscapes involves learning how to paint the sky. Whether our intent leans toward realistic or representational, we learn the details of perception like the sky tends to lighten toward the horizon.

We are encouraged to consider atypical skies ― the non-blue moods of the sky we frequently see.

Painting sky, we sensitize ourselves to shadows and highlights. We are reminded that clouds reflect the light in the sky.

Look at your feet. You are standing in the sky. When we think of the sky, we tend to look up, but the sky actually begins at the earth.
Diane Ackerman
Cloud Study
John Constable, 1822
White light has the visible colors of the spectrum. White light emanating from the Sun is scattered by the gases and particles in the Earth's atmosphere.

Atmospheric gases act as a prism to separate white light into its component colors. The atmospheric prism is mostly nitrogen (78%) and oxygen (21%) with trace gases like argon and water vapor. Particulates can be dust, soot, ash, pollen or salt from the ocean.

Blue light travels as shorter, smaller waves. A cloudless sky appears blue because blue light is scattered more than other colors.
All this time
The Sun never says to the Earth,

"You owe me."

What happens
With a love like that,
It lights the whole sky.

Viewing the sky away from the sun we see light that is bent the most ― a complex spectrum dominated by light of between violet (wavelength of 400 nanometers) and blue (wavelength of 450 nanometers).

Sunset at Montmajour
Vincent van Gogh, 1888
Sunset light travels farther through the atmosphere before it reaches us. More of that light is scattered.

The color of the sun itself changes from orange to red. The cooler, shorter wavelength blue light is completely scattered leaving the warmer, longer wavelengths like oranges and reds on the horizon.

The sky grew darker, painted blue on blue, one stroke at a time, into deeper and deeper shades of night.
Haruki Murakami, Dance Dance Dance