Lighting

Earth's Shadow
Wait For The Right Light

Frank Weston  |  May 1, 2004

The rising sun pushes the earth's shadow down toward the San Juan Mountains near Telluride, Colorado. (Nikon N90s; Nikkor AF 80-200mm f/2.8 D; 20 seconds at f/22; Velvia, ISO 50.)
Photos © 2003 Frank Weston, All Rights Reserved

In the Western US, sunrise and sunset photography can often be especially challenging because there aren't any clouds. Without clouds or haze, the sky simply fades from a very pale, burnished blue to gray. No drama. No flash of color. No spectacular light show. Nothing to add drama and interest to a photograph.

Fortunately, Mother Nature has been kind enough to put on a little show that can help enrich boring blue skies. Not surprisingly, it is the same thing that we photographers work with all the time--light and shadow--only it's in the sky.

The dry air in the arid West, particularly at higher altitudes, allows us to see a phenomenon that frequently occurs when the sun is just below the horizon--a band of pink, transitioning quickly into blue, appears above the opposite horizon. Sometimes intense, sometimes very faint and subtle, this line is the shadow of the earth cast across the atmosphere. The shadow of the planet is projected through the atmosphere the same as shadows of backlit trees are projected through fog. Only this is a much more extreme phenomenon. The lower, shadowed portion of the sky is usually a dark blue to blue gray that transitions very quickly into a pink band that fades into the washed out, pinkish-blue sunlit sky above.

Taking advantage of the earth's shadow adds an unusual artistic element to your composition, breaking up the large negative space created by an empty sky. And if you're fortunate enough to be near water, the subtle hues of the earth's shadow reflected in the water are not to be missed.

Tranquility reigns as the snow-mantled peaks subtly reflect the soft pastels of the earth's shadow. (Nikon N90s; Nikkor AF 80-200mm f/2.8 D; Velvia, ISO 50.)

Catching The Light
Photographing the earth's shadow is surprisingly simple. The earth's shadow seems to be more prominent at sunrise. This is probably because there tends to be less dust and fewer clouds in the air. So most of my images are made before sunrise. In order to photograph the earth's shadow, you need to solidly support your camera to accommodate long exposures. You can expect exposure times of 1/4 sec or more even with the widest aperture.

Metering Options
I set my camera to properly expose the foreground and let the sky take care of itself. I meter the scene in one of two ways. One is to set my camera to meter in Matrix mode (Editor's Note: Intelligent, Evaluative, ESP, etc.) and meter the scene with just enough sky to show the earth's shadow. Compensating for the overall tonal values of the scene as you normally would (decreasing the exposure for predominantly dark subjects and increasing it for predominantly light objects), this usually gives a good exposure for the foreground and a reasonable exposure for the sky. I bracket ±1/2 stop and pick the shot that shows the earth's shadow and foreground to best advantage. The other way I determine the exposure is to use a gray card. This also gives a good overall exposure, but again, I bracket ±1/2 stop. That's it. No magic filters. No fancy techniques.

The subtle shades of the earth's shadow are reflected in a quiet pond near the top of Beartooth Pass on the Wyoming-Montana border. (Mamiya RZ67 II; Mamiya 65mm/Mamiya 1.4x tele; 30 seconds at f/22; Velvia, ISO 50.)

Long Exposure Times
If you're like many landscape photographers who shoot at the smallest aperture to achieve maximum depth of field to keep everything in focus, then very long exposures will be required. A sturdy tripod and sound photographic technique are crucial. Your camera must be very stable and, if possible, operated in the mirror-up mode to avoid camera shake when you trip the shutter. By long exposure, I mean from 1 second up to 60 seconds. The actual time will vary depending on your lens, aperture, and film speed.

Failure Of The Law Of Reciprocity
Naturally, when making long exposures, the question of reciprocity failure of the film comes up. Simply stated, reciprocity failure is when film does not respond to low-light conditions as it does under normal light. Think of making an exposure like filling a water glass. You can fill the glass very fast (a wide aperture and fast shutter speed) or very slow (a small aperture and long shutter speed). Either way, it takes the same amount of water (light) to fill the glass. If you fill the glass extremely slow, when the water faucet is just dripping into the glass, some of the water evaporates before the glass fills. Therefore, it actually takes more water dripping from the faucet to fill the glass than when the glass is filled "normally."

During very long exposures, usually 1 second or longer, you need to compensate for the "evaporating water" by increasing the exposure. There is also a very slight color shift in color films in low-light conditions. This is because the different color layers in the film do not respond
to light in exactly the same way.

Normally the differences are too slight to be seen, but long exposures magnify those tiny differences.

The Rio Grande River in southern Colorado's San Luis Valley reflects the soft pink sky from a fairly sharp earth's shadow. (Mamiya RZ67 II; Mamiya 65mm; 15 seconds at f/32; Velvia, ISO 50.)

Tech Data Guides
Since different films react differently under low-light conditions, it is necessary to check the manufacturer's technical data for the proper correction factor for the film you're using. For my preferred film, Velvia (RVP 50), Fuji recommends adding 1/3 to 1 stop to the exposure and using a 5M to 12.5M color correction filter (Fuji Data Sheet AF3-960E) for exposures of 1 second or longer.

Shooting the earth's shadow, I find that I do not like the results that I get using these corrections. Exposing to get a "normal"-looking exposure tends to look a bit unnatural, making the foreground too bright for the sun being below the horizon. It also washes out the sky, losing the earth's shadow. By underexposing 1/2 stop, the foreground is a little dark, adding a sense of time, emphasizing that the sun is below the horizon while preserving the earth's shadow above the horizon. The slight color shift is usually not noticeable in a natural scene under these lighting conditions. I recommend that you experiment a little to determine what results you prefer.

If you prefer a more normally exposed foreground, a graduated neutral density filter may be necessary to preserve the earth's shadow in the sky. Most of the time, I don't use any filter. All of the photos accompanying this article were taken without any filter or enhancement.

The next time you're faced with a clear, blue-sky sunrise/set, don't despair. Simply turn your back on the sun and look for the earth's shadow just above the opposite horizon. The subtle colors of the earth's shadow can turn a boring blue sky into an interesting band of pink and blue.

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