Camera Obscura

The camera obscura (Lat. dark chamber) was an optical device used in drawing, and one of the ancestral threads leading to the invention of photography. Photographic devices today are still known as "cameras".

The principle of the camera obscura can be demonstrated with a rudimentry type, just a box (which may be room-size) with a hole in one wall, (see Pinhole cameras for construction details). Light from only one part of a scene will pass through the hole and strike a specific part of the back wall. The projection is made on paper on which an artist can then copy the image. The advantage of this technique is that the perspective is right, thus greatly increasing the realism of the image (correct perspective in drawing can also be achieved by looking through a wire mesh and copying the view onto a canvas with a corresponding grid on it). With this simple do-it-yourself apparatus, the image is always upside-down. By using mirrors, as in the 18th century overhead version illustrated, it is also possible to project a right-side-up image. Another more portable type, as in the second drawing, is a box with an angled mirror projecting onto tracing paper placed on the glass top, the image upright as viewed from the back.

As a pinhole is made smaller, the image gets sharper, but the light-sensitivity decreases. With too small a pinhole the sharpness again becomes worse due to diffraction. Practical cameras obscura use a lens rather than a pinhole because it allows a larger aperture, giving a usable brightness while maintaining focus. Some cameras obscura have been built as tourist attractions, though few now survive. Examples can be found in Grahamstown in South Africa, Bristol in England, Aberystwyth and Portmeirion in Wales, Kirriemuir, Dumfries and Edinburgh in Scotland, Lisbon in Portugal, and Santa Monica and San Francisco in California, Havana in Cuba, Eger in Hungary, and Cadiz in Spain.

The principles of the camera obscura have been known since antiquity. Its potential as a drawing aid may have been familiar to artists by as early as the 15th century; Leonardo da Vinci once described the camera obscura. The Dutch Masters, such as Johannes Vermeer, who were hired as painters in the 17th Century, were known for their magnificent attention to detail. It has been widely speculated that they made use of such a camera, but the extent of their use by artists at this period remains a matter of considerable controversy.

A freestanding room-sized camera obscura used by the art department at the University of North Carolina at Chapel Hill. One of the pinholes can be seen in the panel to the left of the door.A freestanding room-sized camera obscura in the shape of a camera is located in San Francisco at the Cliff House in Ocean Beach.

Early models were large; comprising either a whole darkened room or a tent (as employed by Johannes Kepler). By the 18th century, following developments by Robert Boyle and Robert Hooke, more easily portable models became available. These were extensively used by amateur artists while on their travels, but they were also employed by professionals, including Paul Sandby, Canaletto and Joshua Reynolds, whose camera (disguised as a book) is now in the Science Museum (London). Such cameras were later adapted by Louis Daguerre and William Fox Talbot for creating the first photographs.