Slideshow

A slide show is a presentation of a series of still images on a projection screen or electronic display device, typically in a prearranged sequence. The changes may be automatic and at regular intervals or they may be manually controlled by a presenter or the viewer. Slide shows originally consisted of a series of individual photographic slides projected onto a screen with a slide projector. When referring to the video or computer-based visual equivalent, in which the slides are not individual physical objects, the term is often written as one word, slideshow.

A slide show may be a presentation of images purely for their own visual interest or artistic value, sometimes unaccompanied by description or text, or it may be used to clarify or reinforce information, ideas, comments, solutions or suggestions which are presented verbally. Slide shows are sometimes still conducted by a presenter using an apparatus such as a carousel slide projector or an overhead projector, but now the use of an electronic video display device and a computer running presentation software is typical.

Slide shows had their beginnings in the 1600s, when hand-painted images on glass were first projected onto a wall with a "magic lantern". By the late 1700s, showmen were using magic lanterns to thrill audiences with seemingly supernatural apparitions in a popular form of entertainment called a phantasmagoria. Sunlight, candles and oil lamps were the only available light sources. The development of new, much brighter artificial light sources opened up a world of practical applications for image projection. In the early 1800s, a series of hand-painted glass "lantern slides" was sometimes projected to illustrate story-telling or a lecture. Widespread and varied uses for amusement and education evolved throughout the century. By 1900, photographic images on glass had replaced hand-painted images, but the black-and-white photographs were sometimes hand-colored with transparent dyes. The production of lantern slides had become a considerable industry, with dimensions standardized at 3.25 inches high by 4 inches wide in the US and 3.25 inches square in the UK and much of Europe.

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