Inspiration for Bay Sundown Plein Air

Sometimes the real world can become almost abstractly simple—Bay Sundown Plein Air depicts one of these moments. Earlier that afternoon, I had been painting en plein air at one of my favorite locations on Pensacola Bay. As night fell and the light faded, I started wrapping up for the day. But then the glory of the gloaming inspired me to run to my car and grab a new canvas! It’s incredible how much a familiar scene can change during different hours of the day. (That’s what Monet’s Haystacks were all about, right?) I’ll especially never cease to be in awe of the “rainbow sky” (as my Wife and I call it) of clear evenings. The earth’s atmosphere scatters the lengthening rays of the sun into all the colors of the spectrum—the effect is simply stunning.

Sunlight Scattering

(The following information is an excerpt from an article by Stephen F. Corfidi entitled The Colors of Sunset and Twilight. The full version can be found by following this link.)

Clean air is, in fact, the main ingredient common to brightly colored sunrises and sunsets.

To understand why this is so, one need only recall how typical sky colors are produced. The familiar blue of the daytime sky is the result of the selective scattering of sunlight by air molecules. Scattering is the scientific term used to describe the reflection or re-direction of light by small particles. Scattering by dust or by water droplets is responsible for the shafts of light that appear when the sun partly illuminates a smoky room or mist-laden forest. Selective scattering, also known as Rayleigh scattering (after the nineteenth century English physicist Lord Rayleigh), is used to describe scattering that varies with the wavelength of the incident light. Particles are good Rayleigh scatterers when they are very small compared to the wavelength of the light.

Ordinary sunlight is composed of a spectrum of colors that grade from violets and blues at one end to oranges and reds on the other. The wavelengths in this spectrum range from .47 um for violet to .64 um for red. Air molecules are much smaller than this — about a thousand times smaller. Thus, air is a good Rayleigh scatterer. But because air molecules are slightly closer in size to the wavelength of violet light than to that of red light, pure air scatters violet light three to four times more effectively than it does the longer wavelengths. In fact, were it not for the fact that human eyes are more sensitive to blue light than to violet, the clear daytime sky would appear violet instead of blue!