GOLDEN HOUR

Sunlight is actually white, meaning it is composed of every color. The earth’s atmosphere filters the sunlight, and as a result our eyes see the light that passes through this filter. The human eye is sensitive to the different wavelengths of light. We experience each different wavelength as a sensation of color. Every color has its own unique wavelength. (As the name implies, it is the “length” of the wave that varies by color - some short, some long, etc.)

During sunrise and sunset, when the sun is closest to the horizon, it is the farthest point from our eyes. The light from the sun has to travel 10 times farther to reach our eyes. This means the sunlight is passing through much more of the earth’s atmospheric filter.

The different colors of the spectrum, each having a different wavelengths, don’t pass through the atmospheric filter uniformly. Colors with shorter wavelengths get filtered out sooner and colors with longer wavelengths travel father.

You won’t be surprised to learn that the colors with the longest wavelength are yellow, orange and red. During sunrise and sunset these colors appear in larger proportions than any other colors. The other colors, with shorter wavelengths, are filtered by the atmosphere. That is why we have a sense that our surroundings have a golden hue, or tint. The yellow, orange and red colors dominate and blend to create that effect. Hence the term “golden hour.”

So why does my picture of a rose appear to have a background of a tree with orange leaves? At the exact moment of that picture my eye saw green leaves. The reason the leaves appear orange is because of how human vision and camera sensors are designed. They record atmospheric colors very differently.

The human eye and brain compensate for lighting conditions using color constancy, which is a process that automatically adjusts color so objects appear natural. A camera, on the other hand, simply measures the light as it is without applying the same corrections as our eyes and brain do. If a wavelength of light is the wavelength of orange, then the camera records orange.

The eye’s retina has three cones that process light. Each cone processes different wavelengths of light: one cone processes short wavelengths, another medium and the other long wavelengths of light. When one specific light (color) dominates our surroundings, these cones respond to reduce the intensity of that wavelength of light. This prevents the eye from being overwhelmed by one color.

The brain’s visual cortex receives these signals from the retina. It relies on memory and the surrounding context to make corrections to color. For example, in incandescent light a piece of white paper will have a yellow tint. Your brain’s memory knows the paper is pure white, and it corrects the color of the paper by removing the yellow tint. You only see a piece of pure white paper. Your eyes and brain are combining to show you an illusion of white paper by removing the yellow tint caused by the incandescent light.

In my picture of the rose against a background of trees here’s what happens. The atmosphere has an intense orange hue, or tint, from the setting sun. This is because the sun on the horizon is at its farthest point from our eyes and more yellow, orange and red wavelengths of light are present than any other colors. But the retina mutes the intensity of the orange light, and the brain uses memory and surroundings to restore the green to the leaves - the phenomenon of color constancy.

The camera, on the other hand, does not have the complex functioning of the human eye or brain. Hence, the camera captures the true state of the atmosphere, which is dominated by the colors with the longest wavelengths that passed through the atmospheric filter. Those colors are yellow, orange and red. Unlike the brain, the camera cannot rely on memory to correct color in any way.