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Monday, November 16, 2009

Into The Caves Of Patagonia


New camera technology comes to the rescue when one of the world’s pristine wonders is photographed

This Article Features Photo Zoom


Testament to the fairly constant level of the lake over time, a column of marble stands between wider slabs above and below the water’s surface. Fins of different minerals ring the column. Canon EOS 10D.
The HDR Experiment
The first day, George tries a new idea, multiple-image composites for high dynamic range (HDR). The HDR technique requires three exposures in sequence, one exposed for the middle-range light, one two-stops overexposed for the dark areas and one two-stops underexposed for the bright areas. Ideally, when the three exposures are composited in Photomatix Pro software, the full tonal range will be revealed. It’s a process best managed from a tripod to assure sharp captures and identical frames that will match perfectly when composited. The question: Would it work without a tripod, shooting at the slow shutter speeds dictated by the deep shadows, with the photographer standing in a small boat?


From the desperately steep road that winds down to Bahía Mansa, a first sighting of stony cliffs and the mushroom-cap islands that cover the marble caves. Lago General Carrera’s brilliant blue color is due to the glacial melt from the Andes Mountains, seen in the background. Canon EOS 50D.
A wide-angle lens is needed to capture the scene in the confined areas, so George chooses a 17-40mm Canon zoom. To minimize movement in the handheld rig, George sets the EOS 5D Mark II to capture the three exposures automatically in quick succession with only one press of the shutter button. But in this situation, the overexposed captures yield a shutter speed as slow as 1⁄15 sec., vulnerable to the effects of camera movement in the rocking boat. Our orientation to the subject demands the widest angle of view, but the 17-40mm doesn’t have image stabilization. That night, as George reviews the day’s work, he struggles to composite the images. They’re matched and sharp in the center, but out of register at the edges because even the slightest movement of the boat exaggerates the peripheral distortion common to a wide-angle lens. At last, he concedes: The experiment is a failure or, as we prefer to call it, a learning experience.

Fortunately, the day’s work isn’t lost because the exposure for the midtones can be used when optimized in Lightroom and Photoshop. Nonetheless, HDR is abandoned for the rest of the shoot, much to George’s disappointment, as he had envisioned a number of creative interpretations of the caves that could only be achieved with that process.

Expanded ISO To The Rescue
In the following days, George concentrates on using the EOS 5D Mark II’s expanded ISO capability as a way to sharply capture the intricate forms and details in the dark grottoes and caverns. This works well in areas where the tonal range is dim to dark, but not when exceptionally bright areas are part of the scene. In his previous tests of the EOS 5D Mark II [see “Sharp Is King,” OP, Jan./Feb. 2009], he had determined that ISO 800 would yield excellent quality while allowing the necessary slow shutter speed of 1⁄30 to 1⁄90 sec. at ƒ/11, the aperture necessary to generate sufficient depth of field to render the entire composition sharp from foreground to background. In tighter quarters, this setup enables George to use the Canon 15mm fisheye with extraordinary results.

One of the greatest challenges of photographing in the confinement of the caves is recording in full detail the complex length of a dramatic wall of marble, with all its undulations and patterns, its arches, windows, crevices and shadows, and its sharp, protruding edges. Here, George applies one of his favorite techniques, the close-range panorama. Capturing multiple closely overlapping vertical images generates a series that, when composited in Panorama Maker 4 Pro (5 is now available), yields high-resolution panoramas that allow the viewer to see all the detail of the caves that we could see from our boats. Even though the panoramas are taken with the 17mm lens, overlapping the images by 50 percent gives the software sufficient information to be able to resolve and match the distorted upper and lower edges of the extremely wide-angle vertical captures.

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