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Photographer's Note

THE VISIBLE SPECTRUM

Niagara Falls, on the border between the United States and Canada, is in reality three separate falls — American, Bridal Veil, and the massive Canadian or "Horseshoe Falls." Each minute 5720 cubic-meters of water pours over the 70 m (180 ft) high edge, not counting a volume three times as large that is diverted to drive hydroelectric generators. In the United States there are much higher waterfalls, e.g. at Yosemite Park (total height 740 m or 2425 ft), but none has the flow rate of the Niagara. Also in contrast to the Niagara, the much larger Victoria Falls in Africa features fifteen separate falls, with a peak flow of 425,000 cubic-meters per minute. Finally, there is the more majestic Iguassu in South America, on the border of Argentina and Brazil, pouring 380,000 cubic-meters per minute (or 18 times more than does Niagara Falls). An extraordinarily beautiful photograph of the Iguassu was posted by bwj as Devil’s Throat three months ago. Nonetheless, the Niagara, hosting as many as 20 million visitors annually, is arguably the most famous of all waterfalls in the world.

This past week I visited the area around the City of Buffalo in New York State, ostensibly to give a talk at the State University of New York in Fredonia, and a friend from Fredonia was gracious enough to drive me to the storied falls. In shooting the photograph, I stood near the edge of the American Falls, where the water pouring into a seemingly bottomless pit produced the spray, and light rays dispersing through the water droplets in the spray created the rainbow. The colors range from the longer wavelength reddish glow in the upper bands, changing gradually to turquoise in the middle bands, and finally the shorter wavelength violet in the lower. (These colors represent just the ‘visible region’ of the electromagnetic spectrum.) For the reader with a technical mind, a rainbow is a composite effect of rays of white light striking numberless spherical droplets of water and becoming dispersed. Light rays are refracted twice (across the outer surface of a droplet as they enter and leave the droplet), and reflected once (at a diametrically opposite area in the inner surface). Ultimately, it is the composite image the eye receives from multiple droplets that reveals the bands of colors. A simple diagram in the following link may be helpful in understanding the foregoing explanation.

In this image, shot with a Nikon D200, the falls themselves are not visible (they are off to the left of the cliff). But exactly twenty-two years ago in late April 1987, I had taken a photograph from almost the same vantage point with another good camera, a non-digital Nikon F, where the Edge of the falls was featured. In the present photo it is the flock of seagulls dancing in the mist that I sought to capture. A lone seagull flying below the rainbow made this the best of half-a-dozen images that I shot. What appears in the background in this photo is neither the falls, nor noise, but that all-pervasive mist.

PS. I changed the title of this image from "a visible spectrum" to "a footbridge between cliffs," after reading the clever metaphor by Diane Chesnel (clio). Many thanks Diane.

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Additional Photos by Bulent Atalay (batalay) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 6777 W: 471 N: 12149] (41261)
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