A stereopticon is a slide projector or "magic lantern", which has two lenses, usually one above the other. These devices date back to the mid 19th century, and were a popular form of entertainment and education before the advent of moving pictures. Americans William and Frederick Langenheim introduced stereopticon slide technology—slide shows of projected images on glass—in 1850. For a usual fee of ten cents, people could view realistic images of nature, history, and science themes. The two lenses are used to dissolve between images when projected. At first, the shows used random images, but over time, lanternists began to place the slides in logical order, creating a narrative. This "visual storytelling" with technology directly preceded the development of the first moving pictures.
The term stereopticon has been widely misused to name a stereoscope. A stereopticon will not project or display stereoscopic/three-dimensional images on cards. All stereopticons can be classified as magic lanterns, but not all magic lanterns are stereopticons.
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