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Tuesday, July 26, 2011

Luck Favors The Prepared

When you’re ready for anything, good photographs tend to come together

Labels: How-ToColumnTech Tips
The Camera Never Sleeps
It's hard to find a darker place than Botswana's Okavango Delta, and because rain is scarce, the skies are usually clear. The vista of stars is enhanced by African landscape icons such as baobab, palm and acacia. A drawback of photography in this environment is finding a safe place to photograph for an extended period at night, when those aforementioned animal subjects are out looking for dinner.

The members of our group took advantage of this unusual opportunity by photographing from within the camp. But one night at Mombo Camp, where the rule is that no one can be in the field after dark, we developed a scheme to photograph star trails around our favorite baobab tree (affectionately named Bob by the staff). At sunset, each participant's camera was clamped to a rail on a single Land Rover, which was left in position while the cameras took a continuous series of 30-second exposures. The vehicle and cameras were collected by an authorized staff person several hours later, and we processed our images the next day. Should you find yourself in a similarly dark location, here's how you would go about capturing the skies.
With recently released high-end DSLRs, expanded ISO capabilities are critical factors in achieving sharp low-light images of wildlife with long lenses. And if you spent the night photographing the Milky Way, the 3200 ISO you used in the dark isn't likely to be the right choice in the warm light of morning.
Milky Way. You need a base to your image, so choose an interesting foreground that will be rendered as a silhouette or painted with light, with the Milky Way flowing through the background. Choose a fast wide-angle lens, preferably an ƒ/1.4, at its widest aperture; a 24mm ƒ/1.4 Nikon or Canon lens is ideal. The sensitivity of the camera is critical, so an ISO of 3200 is important, but going higher will add a lot of noise that interferes with the rendition of the stars (what's that green planet there?). Due to the rotation of the earth, the exposure can't be any longer than 30 seconds or your pinpoint stars will become streaks of light. The ending result is an interesting foreground with a brilliant sky filled with far more stars than the unassisted human eye can see.

Star Trails.
Once again, you need a foreground that will anchor your image and emphasize the movement of the stars through the frame. To generate a circular star trail, you need to point the camera to the north in the Northern Hemisphere (the North Star is the best guide) and to the south in the Southern Hemisphere (the Southern Cross). For our Mombo adventure, we used an iPhone app to locate true south. Ideally, we'd like to portray the stars' apparent movement (we know it's really the earth that's moving) during a long exposure that generates a single circular line, but doing so increases the amount of noise generated by the digital camera. A way to accomplish a similar result with less noise is to use an intervalometer to capture a series of 30-second exposures at one-second intervals over a several-hour period (or until your battery dies). The series of images is blended together in Photoshop using the Lighter Color Blend mode to achieve a single image with complete star trails. Be sure that Noise Reduction options are turned off during the capture because this will increase the interval between captures to 31 seconds, long enough to cause a break in the trail.

Collegiality, logistics and location are essential elements for a successful group photography expedition, and on this trip we had the best of all. Sincere thanks to our wonderful companions on our African adventure (you know who you are), and to Journeys Unforgettable (www.journeysunforgettable.com) and Wilderness Safaris (www.wilderness-safaris.com), who made it possible.

For information about upcoming seminars and digital-imaging workshops, visit www.georgelepp.com. If you have any tips or questions, address them to: OUTDOOR PHOTOGRAPHER, Dept. TT, George Lepp, 12121 Wilshire Blvd., Suite 1200, Los Angeles, CA 90025-1176 or online at www.georgelepp.com.

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