The camera obscura: a chronicle

Historical Significance: The camera obscura (Latin; camera for "vaulted chamber/room", obscura for "dark", together "darkened chamber/room"; plural: camera obscuras or camerae obscurae) is an optical device that projects an image of its surroundings on a screen. It is used in drawing and for entertainment, and was one of the inventions that led to photography and the camera. The device consists of a box or room with a hole in one side. Light from an external scene passes through the hole and strikes a surface inside, where it is reproduced, rotated 180 degrees (thus upside-down), but with colour and perspective preserved. The image can be projected onto paper, and can then be traced to produce a highly accurate representation. The largest camera obscura in the world is on Constitution Hill in Aberystwyth, Wales. Using mirrors, as in the 18th-century overhead version (illustrated in the History section below), it is possible to project a right-side-up image. Another more portable type is a box with an angled mirror projecting onto tracing paper placed on the glass top, the image being upright as viewed from the back. It has its origin in ancient Greece.