Diffraction Fringe
by Galen Rowell
Outdoor Photographer, July | August 1998

Outdoor optical effects keep nature photography interesting. Exceptional phenomena–rainbows, glories, and diffraction effects–are what first come to mind, but more common effects–haze, shadows, and blue midday light–can be the most challenging to render into an appealing photograph. Some fine art critics judge exquisite photographs of rare phenomena as simply "cheap shots" of effects packaged and delivered by nature. In their world, a perfect rainbow or diffraction fringe painted around a figure indeed appears contrived, but in editorial photography a rare moment is perceived to represent what a fellow human being witnessed. For example, Eddie Adams' 1968 image of the roadside execution of a Viet Cong almost instantly changed the face of the war after it was seen on TV and front pages around the world. No artist's conception of the same event could have had such power.

A vocal fringe of the fine-art world would like photographers to show nature as average, never exceptional. In a recent "Art Issues" editorial Rebecca Solnit writes, "Yosemite Valley, in its most usual condition, is a green or brown landscape with indifferent air quality." She goes on to describe Galen Rowell as one of those wretched photographers "who use colored lenses to depict a souped-up, hot rod-bright world." Poor Rebecca must never have gotten up early enough to see alpenglow at dawn or to see the natural features crystallize during the clearing of a storm when the atmospheric perspective taught in art schools vanishes in the absence of haze. My best-selling photograph of Yosemite was made without the bias of any filter or highly saturated film almost thirty years ago. I have yet to replicate the clear, rich colors of Yosemite alpenglow touching 1970 Kodachrome at the end of a ten-day storm. Exceptional outdoor optical effects make exceptional photographs.

I found even more clear air last summer in the High Sierra on the summit of 13,080-foot Mt. Darwin shortly after dawn. The sky had near-perfect clarity after a windstorm. I tested the potential for a diffraction fringe with my "little finger" rule. If I can block the sun entirely with the tip of my baby finger at arm's length and see blue sky all around its outline, conditions are ripe for a diffraction fringe to bend the sun's rays around a backlit subject at a proper distance.

Peter Croft and I had reached the summit of Mt. Darwin after starting out by headlamp to first climb neighboring Mt. Mendel. We were attempting the first-ever traverse of the crest of the Evolution Range. After doing all seven peaks along the Sierra crest, I returned to camp at 3 PM with bleeding fingers worn through all layers of skin. Peter continued on over several more peaks, reaching camp at 7 PM.

Without prior preparation, I never would have spotted the fantastic light or made the photograph that appears here. Having scouted the scene on the previous afternoon, I convinced Peter, who was itching to move on, to stand on the summit pinnacle for a minute holding his ice axe. I scrambled to fit myself within his shadow on the side of a cliff sixty feet away-the magic distance.

The day before, I had climbed Mt. Darwin by a different route and noticed the potential for a diffraction fringe around a climber on the summit about an hour after sunrise. When the sun is closer to the horizon, the air is always too disturbed for a good diffraction fringe. That's why the sunlight turns reddish as blue rays are scattered away. Only when the sun shines through air devoid of moisture, smog, and dust-all those things normally present at sea level-can enough direct rays bend around an object to cause a strong fringe.

Finding a low enough position in your subject's shadow 60 feet away at mid-day is almost impossible. Steep, open landscapes an hour or two after dawn have the best odds. The gradual bending of light rays cannot be clearly seen much closer than 60 feet, and from farther away the width of the sun begins to destroy the shadow and the effect. The ideal geometry is so rare on mountain summits that I've only found it twice during 40 years of climbing in the High Sierra.

The way I saw Peter through my lens stopped down so as not to be blinded by the sun is almost exactly what I see in the photograph-a beauty that I discovered for myself in the natural world. Virtually all scenic photographs include outdoor optical effects: sunrises, sunsets, shadows, reflections, godbeams, rainbows, glories, and seemingly ordinary blue skies and white clouds. Understanding what causes these phenomena allows a photographer to maximize their appearance on film. Even without any knowledge of the physics of light, a photographer quickly discovers that the true beauty of a Yosemite does not record on film in that hazy average light touted as reality by an art critic.

Despite postmodern stagnation in the art world, civilization reached its present level through the efforts of men and women who searched out order from chaos to unfold hidden beauty in both the arts and the sciences. The pursuit of beauty is just as present in the elegance of Einstein's theory as in the "terrible lucidity" that came to Van Gogh as he painted. The nature photographer's task is to record the inner vision that empowered a Van Gogh as light and form on film that can communicate such moments to others. At its best, nature photography transcends mere visual information in the same way that poetry can transcend the meaning of words to communicate not only what's out there, but how it feels spiritually and emotionally.

The public seems to believe that photographers only record what they are seeing in front of them. The search for outdoor optical effects belies the common misconception that anyone who happened to be there could take pretty much the same picture. Neither Peter Croft nor I would have seen a diffraction fringe on Mt. Darwin without creative forethought.

Outdoor optical effects can be truly personal. Two people standing beside each other see two different rainbows, reflected back from different raindrops. The specter of the Brocken, in which a shadow surrounded by a glory is projected into mist, is also an individual experience where each person is seeing only their own shadow. Indeed, shadows become ever so individual when they spoil front-lit photographs of close subjects in low-angled light.

Shadows are also the key to understanding how to photograph the diffraction fringe. Place your camera inside the shadow of your subject's head at the proper distance in rare point-source sunlight. That's the easy part. The hard part is that open-ended potential which leads me to lug my camera along on every adventure.

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