Shadows

Notes from James Gurney blog

 

Color in Shadows

Here is a good example of the color of shadows, something that cameras can't capture as well as the human eye.

The sources of light in shadow are very distinct: blue sky, orange ground, and white architecture, and there are white planes facing in all directions.

The direct sunlight is coming from behind and to the right, making the illuminated surfaces a bright white.

There are two main sources of light in the shadow: warm light bouncing up from the ground, and blue skylight from above.
In the shadow, up-facing planes are cool and down-facing planes are warm. The reason for the shift in color temperature is that the up-facing planes pick up more of the sky color and the down-facing planes receive more of the ground color.

At letter (A), left, the upfacing shadow planes on the roof are receiving mostly blue sky light.

(B) and (C) are down-facing planes. The light is mostly warm-colored bounced light from the ground.

The far side of the arch (D) is getting very strong reflected illumination from the brightly lit opposite side of the arch, as well as apparently some greenish light from the water in the canal (not visible in this view) passing beneath the gate. 

At (E), the columns are a little bit lighter than other parallel vertical surfaces. They're projecting outward, receiving quite a lot of light from all directions, both warm and cool. 

Complementary Shadows

In most sunny conditions, shadows really are in a complementary color range compared to the sunlit surfaces because they're lit by the relatively blue skylight.

By contrast, the sunlit surfaces are lit by the sum of the sunlight and the skylight, with the sunlight dominating. It's easy to demonstrate this with a camera that is color balanced to sunlit white paper. When you take the same white paper and photograph it again in shadow, it's clearly bluer.

The effect is heightened late in the day as the sun is lower in the sky. More of the short-wavelength is scattered out of the sunlight, leaving more orange or red light, and making the color contrast between light and shadow more obvious.

(A brief caution on the above: the shadow side of any object receives not only skylight, but also reflected light from other sources, so if those sources of reflected light are very warm, and the sky is blocked by trees or clouds, the shadow might be very warm, too.)

At the same time, our visual system is set up in such a way that exposure to any color causes adjacent colors to appear complementary, so a yellow square next to a gray square will make the gray square look bluer.

This is an effect I like to use a lot, not only to simulate the "Golden Hour" time of day, but also in small ways, to alternate relatively warm and cool colors throughout a picture.