Color, Light and the Magic Hour
by Galen Rowell
Outdoor Photographer, November 1999

Every landscape photographer worth his salt knows to foresake the noonday sun for the ever-changing light of dawn and dusk. Few, however, have a working knowledge of what makes these magical hours so attractive to the eye. Fewer still fathom why film transforms this natural magic into yet another dimension that can appear exquisitely mystical or dumfoundingly mundane.

My own learning curve is a case in point. Back in the sixties, I'd head off during magic hour with an arsenal of camera gear in my pack, sense that the light was beginning to turn warm, then only at the last minute pull out the heavy artillery to isolate an orange orb on the horizon in the center of a red glaze. My results were predictably trite. The visual power of magic hours involves so much more than selecting out a great sunrise or sunset by itself.

Early on, I realized that there was no simple trick that would turn one of the stark, raving beautiful light shows I was regularly witnessing into a fine photograph. That began to happen only after I gained a greater understanding of why I was so attracted to red light, why I tended to ignore what was happening to other parts of the atmosphere at the same time, and how my film was coding the colors of the scene before me in an entirely different way than my visual system.

Consider insects disturbing a party in your backyard by buzzing around a bare light bulb over the dinner table. They only start doing it during magic hour when they begin to mistake the bulb for the sun. You can't stop them, because they're on autopilot with guidance systems that keep them circling until you turn off the light or shoot them out of the sky with bug spray.

Humans also respond to a built-in visual bias toward brightness and hues at the warm end of the spectrum that can make them behave rather mindlessly with a camera in hand. But there's a difference. The bugs have no options. For them, the visual representation of an apparent sun triggers a predictable physical reaction. We have an infinity of choices. Creative photography begins where we stop blindly responding to the strongest visual representation before us. We can choose whether to mindlessly shoot or to use the stored visual memories of a lifetime to guide us toward a unique personal vision.

The ancients worshipped the sun, but couldn't look directly at it during the day. Thus the hours when the sun's intensity came to be attenuated near the horizon so that it could be clearly observed came to be considered spiritual. Legends were passed down about the otherworldly sources of the mystical colors. Not until the scientific revolution did logical explanations emerge.

In the mid-nineteenth century, a British scientist who climbed and explored mountains in his spare time came up with a plausible theory. John Tyndall, a close confidant of Darwin and Huxley, was a broad-spectrum kind of guy, so to speak. His habit of looking beyond the obvious in all the operations of the natural world paid off well in biology, where he helped verify Pasteur's germ theory of disease with experiments that negated the prevailing idea of spontaneous generation of life forms. In geology, his expertise on Alpine glaciers led him to Yosemite, where he validated John Muir's controversial theory that glaciation had sculpted its features. As a pioneer in atmospheric physics, he explained what became known as the "Tyndall effect," which accounts for light beams becoming visible from the side as they pour down from clouds, up from searchlights, or, in today's world, from lasers. He is less remembered for his counter-intuitive theory that red sunsets are caused by the same scattering of light which creates blue skies.

Tyndall hypothesized that the same dust particles in the air that make light beams visible must scatter more blue light than red light at the higher-energy end of the spectrum. It made perfect sense: the scattered light of the sky and shadows is blue, while the transmitted light of the sun that has passed through lots of dust particles is red. Case closed.

Enter John William Strutt, later Lord Rayleigh, Nobel laureate for studies of atmospheric gases. After doing the math on light scattering by particles, he concluded that most dust lacked the precise size relationship to wave length to account for the profound blue sky effect. Tiny air molecules are the cause of what is now known as "Rayleigh's scattering." Blue light with a wave length around 450 nanometers is 3.2 times more likely to be scattered by air molecules than red light of 600 nanometers. When dramatic color sorting occurs as sunlight travels through the thickest air near the horizon, all white light vanishes and magic hour arrives.

Because our visual system has the greatest response to yellows and reds, we tend to pay the most attention to them until a certain moment in twilight when their intensity has fallen well below that of the blues. Suddenly, we're aware of a magical mixture of warm and cool tones, but it's too late for prime photographs, which should have been made before the saturated pinks and reds faded.

Whenever you're responding to warm light coming over the horizon, you're also unconsciously taking in the blues and violets in the majority of the scene. A photograph showing both warm and cool tones will appear more realistic and dramatic, but only if a graduated neutral-density filter is used to hold back the brighter warm areas of the sky so that it's possible to see detail in the blue shadows. The accompanying image of a Himalayan blue pine silhouetted at magic hour in the Khumbu Valley of Nepal was made with a soft-edged, two-stop SinghRay grad filter.

Now let's return to that backyard light bulb and consider what happens if we try to take a photograph of people sitting beneath it on daylight film. An amber wash that we didn't see permeates the entire scene. This happens because film has a fixed color response to the wave length of light, but our eyes do not. Even though the bulb seems white when you're close to it, it is giving off the color temperature of natural light about 20 minutes before sunset. So if those warm colors that you can't see will appear on your film under artificial light, they'll also appear without being seen 20 minutes before sunset in natural light, adding a cast that is far more pleasing on landscapes than faces.

We begin to see an overall orange or red cast only during the peak minutes of magic hour, as the wave length of light goes out of gamut for our biological white-balance system. Of course we can also see yellows and reds outdoors at noon, but only from surfaces that reflect the proper wave length, not from the natural light itself, which appears boringly white.

Next time you're out during magic hour, don't let yourself go buggy over warm light. Make your eyes adjust to the blue end of the spectrum by looking into the shadows. Then when you glance toward the warm tones, they'll appear as rich as on Velvia or E100VS for half a minute or so, until your visual system adjusts. When you look at the blues again, they'll also have the heightened appearance of film for a bit. Taking control over your visual experience not only helps you previsualize magic-hour photography, but also gives you far richer memories, and that's really what life's all about.

Galen’s columns are reproduced on our web site courtesy Outdoor Photographer.
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