The camera obscura is an optical instrument that was the forerunner of the modern photographic camera. It can range in size from a small tabletop device to a room-size chamber. The term is Latin for 'dark room', which describes the simplest form of the camera obscura, a darkened room into which light is admitted through a tiny opening in one of the walls or windows. An inverted image from the outside world appears against the wall or screen opposite the opening. The principle of the camera obscura has been known since ancient times, and the device was used for viewing astronomical phenomena such as solar eclipses form at least the thirteenth century. During the eighteenth century the camera obscura enjoyed widespread popularity, and large camera obscuras were constructed for use as public entertainments.