English: Brothers William and Frederick Langenheim opened a daguerreotype studio in Philadelphia in 1841-1842 and quickly became the city's most celebrated photographers. Known for their technical expertise, the Langenheims pioneered a technique of handcoloring daguerreotypes in 1846 and invented a system of making negatives and positive son glass in 1848-1850. They also introduced stereoscopic photography to the American public in 1850. The Langenheim brothers were the first photographers to practice William Henry Fox Talbot's Talbotype process in the United States. Although a few Americans had experimented with photographs on paper in the 1840s, the daguerreotype process eclipsed paper photography in the United States. William Langenheim visited Talbot in the spring of 1840, and in May of that year Talbot sold his American patent to the Langenheims. In the ensuing months the Langenheims made both portraits and views using Talbot's method while attempting to sell Talbotype licenses to other American photographers. By early 1850 they had succeeded in interesting only a handful of other firms in the process and were forced to declare bankruptcy. (The National Gallery of Art)
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