HOW THEY WORK: Stereoscopic, or 3D photography, recreates the illusion of depth by taking advantage of the binocularity of human vision. Because our two eyes are set apart, each eye sees the world just a bit differently. Our brains combine these two different eye-images into one, a phenomenon that enables us to "see," ever so slightly, around the sides of objects, providing spatial depth and dimension. Stereoscopic views consist of two nearly twin photographs -- one for the left eye, one for the right. When they are viewed though a special lens arrangement (a stereoscope) our brains combine the two flat images and "see" the illusion of objects in spatial depth.

HISTORY: Stereoscopic views were produced by the millions between the 1850s and the 1930s. Their popularity soared when Queen Victoria and Prince Albert were presented with a stereoscopic viewer at the Crystal Palace exhibition in 1851. Soon after, the American jurist Oliver Wendell Holmes called for the establishment of "special stereographic collections just as we have professional and other libraries." Independent and entrepreneurial photographers broke into the growing market for illustrations of all types. Local history and events, grand landscapes, charming genre scenes, portraits of exceptional people, and views of architecture streamed from studios around the world. War and natural disasters such as floods, fires and earthquakes were recorded in stereo views. By the 1890s, humor and sentimentality came to dominate the genre market and Underwood & Underwood and Keystone documentary views became ubiquitous, covering landscape, travel, and the growth of cities. Though independent publishers and itinerant cameramen thrived throughout both periods, the camera work by the end of the century attained a uniformity of appearance that prefigured wire service and publicity photography. In contrast, the artistic and enterprising work of the earlier period make stereoscopic views even more interesting for the discrete photographic visions and regional practices that created it. Stereo views declined in the 1920s and 1930s with the rise of movie newsreels and popular illustrated magazines such as Life.

ENTERTAINMENT AND INFORMATION: Just as the television industry for the past 50 years has addressed the diverse entertainment tastes and far-ranging information needs of a complex audience, so a century ago, stereoscopic views entertained and enlightened a similarly broad and eclectic audience, and, often for the same types of profit. During the period between the 1850s and the 1910s, stereos were a mainstay of home entertainment, perhaps second only to reading as a personal leisure activity. Like television, stereos were an intimate medium viewed by individuals or small groups at home, or at churches, schools or clubs. Stereoscopes varied from small, wooden, hand-held devices for viewing single images to large cabinet-size pieces of furniture that could display a changing series of fifty or a hundred views. The subject matter of stereoscopic views was boundless, appealing to many specialized interests. Like television in its present diversity, stereos accommodated tastes ranging from vulgar to refined, from simple to scientific. Production quality was also wide - from exquisitely sharp original silver prints to indistinct, cheaply produced, often pirated, copies. The makers of stereos were equally diverse. Into the 1880s they ranged from eager amateurs photographing family scenes for private distribution to the famed camera artists of the day who demanded high quality publishing and distribution and got it. By the 1890s, the photographers tended to be skilled and enterprising professionals who either sold their images to large commercial producers or worked anonymously under contract for them.

STEREO VIEWS IN RESEARCH: As a visual resource, stereoscopic views are valuable for the broad community of students, scholars, specialists, and laymen whose research or interests require visual documentation or illustration. The small size of the stereo camera and the public's interest in stereo views produced a more journalistic approach to image-making on the part of stereo photographers. Often, the subject matter of stereo views is simply not found in larger format photography. Stereoscopic views include topographic views, local history, events, industries and trade, costume, urban and country life, and portraits. Also, stereos span eighty years of early photographic practice and are themselves an important source for further researching the history of the photographic medium itself. In addition, stereo views have the potential to reveal the way the world appeared through the photographers' and audiences' preconceptions even as they mirror that long-vanished world's physical and contextual reality. Stereographs continue their expository and illustrative functions on many levels, inviting further use and study.