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Wired magazine has a new article:

1848 Daguerreotypes Bring Middle America’s Past to Life

n 1848, Charles Fontayne and William Porter produced one of the most famous photographs in the history of the medium — a panorama spanning some 2 miles of Cincinnati waterfront. They did it with eight 6.5- by 8.5-inch daguerreotype plates, a then-new technology that in skilled hands displays mind-blowing resolution.

Fontayne and Porter were definitely skilled, but no one knew just how amazing their images were until three years ago, when conservators at George Eastman House in Rochester, New York, began restoration work on the deteriorating plates. Magnifying glasses didn’t exhaust their detail; neither did an ultrasharp macro lens. Finally, the conservators deployed a stereo microscope. What they saw astonished them: The details — down to window curtains and wheel spokes — remained crisp even at 30X magnification. The panorama could be blown up to 170 by 20 feet without losing clarity; a digicam would have to record 140,000 megapixels per shot to match that. Under the microscope, the plates revealed a vanished world, the earliest known record of an urbanizing America.

Daguerreotypes start as copper plates with a thin, mirror-polished coating of silver that’s been exposed to halogen gas (iodine or bromine) to make silver halide. Light hitting this compound knocks an electron loose, which attaches to a silver ion, forming a neutral silver atom. The result is that all the places on the plate exposed to light are clusters of pure silver, and the rest is silver halide.

Ross Messing, Xiaoqing Tang, Paul Ardis

Next, the exposed plate is held over a warm pool of mercury (don’t breathe!). The mercury combines with the silver atoms, creating the equivalent of a digital image’s pixel: a tiny “grain” between 150 and 800 nanometers in diameter that scatters light, making areas of the surface that were exposed to more light appear brighter. Finally, the plate is soaked in sodium thiosulfate, which washes away the unexposed silver halide, leaving dark regions — the image’s blacks and grays.

Now Fontayne and Porter’s daguerreotypes are stabilized and its details restored — 21st-century technology rescued an image from the 19th. The Cincinnati Public Library plans to make a zoomable version available online in the next year.

Photos: Daguerreotypes courtesy of the Public Library of Cinninnati and Hamilton County