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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. In English, today's photographic devices are still known as "cameras".
The principle of the camera obscura can be demonstrated with a rudimentary type, just a box (which may be room-size) with a hole in one side, (see pinhole camera 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 in the Discovery and Origins section, it is also possible to project an up-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 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 camerae obscurae use a lens rather than a pinhole because it allows a larger aperture, giving a usable brightness while maintaining focus.

Contents

Discovery and origins

History

Tourist attractions

References

Sources

See also

External links

Discovery and origins

A Persian scientist named Abu Ali Al-Hasan Ibn al-Haitham (965-1039 AD), known in the West as Alhacen, is credited with the discovery of the camera obscura while carrying out practical experiments on optics in his ''Book of Optics''.Nicholas J. Wade, Stanley Finger (2001), "The eye as an optical instrument: from camera obscura to Helmholtz's perspective", ''Perception'' '30' (10), p. 1157–1177. In his various experiments, Ibn Al-Haitham used the term “''Al-Bayt al-Muthlim''”(Arabic: البيت المظلم), translated in English as dark room. In the experiment he undertook, in order to establish that light travels in time and with speed, he says: “If ''the hole was covered with a curtain and the curtain was taken off, the light traveling from the hole to the opposite wall will consume time.”'' He reiterated the same experience when he established that light travels in straight lines. The most revealing experiment which indeed introduced the camera obscura was in his studies of the half-moon shape of the sun’s image during eclipses which he observed on the wall opposite a small hole made in the window shutters. In his famous essay "On the form of the Eclipse" (''Maqalah-fi-Surat-al-Kosuf'') (Arabic: مقالة في صورةالكسوف) he commented on his observation "The ''image of the sun at the time of the eclipse, unless it is total, demonstrates that when its light passes through a narrow, round hole and is cast on a plane opposite to the hole it takes on the form of a moon-sickle''”.
In his experiment of the sun light he extended his observation of the penetration of light through the pinhole to conclude that when the sun light reaches and penetrates the hole it makes a conic shape at the points meeting at the pinhole, forming later another conic shape reverse to the first one on the opposite wall in the dark room. This happens when sun light diverges from point “ﺍ” until it reaches an aperture “ﺏﺤ” and is projected through it onto a screen at the luminous spot “ﺩﻫ”. Since the distance between the aperture and the screen is insignificant in comparison to the distance between the aperture and the sun, the divergence of sunlight after going through the aperture should be insignificant. In other words, “ﺏﺤ” should be about equal to “ﺩﻫ”. However, it is observed to be much greater “ﻙﻁ” when the paths of the rays which form the extremities of “ﻙﻁ” are retraced in the reverse direction, it is found that they meet at a point outside the aperture and then diverge again toward the sun as illustrated in figure 1. This was indeed the first accurate description of the Camera Obscura phenomenon.

In camera terms, the light converges into the room through the hole transmitting with it the object(s) facing it. The object will appear in full colour but upside down on the projecting screen/wall opposite the hole inside the dark room. The explanation is that light travels in a straight line and when some of the rays reflected from a bright subject pass through the small hole in thin material they do not scatter but cross and reform as an upside down image on a flat white surface held parallel to the hole. Ib Al-Haitham established that the smaller the hole is, the clearer the picture is.

History

Although the principles of the pinhole camera have been known since antiquity, the camera obscura was first described by Ibn al-Haitham (Alhacen) in his ''Book of Optics'' (c. 1000). Several decades after Ibn al-Haitham's death, the Song Dynasty Chinese scientist Shen Kuo (1031-1095 AD) experimented with camera obscura, and was the first to apply geometrical and quantitative attributes to it in his book of 1088 AD, the ''Dream Pool Essays''.^[1] Its potential as a drawing aid may have been familiar to artists by as early as the 15th century; Leonardo da Vinci (1452-1519 AD) described camera obscura in ''Codex Atlanticus''. Johann Zahn's ''Oculus Artificialis Teledioptricus Sive Telescopium'' was published in 1685. This work contains many descriptions and diagrams, illustrations and sketches of both the camera obscura and of the magic lantern.

A freestanding room-sized camera obscura in the shape of a camera located in San Francisco at the Cliff House in Ocean Beach (San Francisco)

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, recently revived by the Hockney-Falco thesis.
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.

Tourist attractions

Some camera obscura have been built as tourist attractions, often taking the form of a large chamber within a high building that can be darkened so that a 'live' panorama of the world outside is projected onto a horizontal surface through a rotating lens. Although few now survive, examples can be found at the following locations:

★ Grahamstown in South Africa

★ the Observatory in Bristol

★ Portslade village and Eastbourne Pier in England

★ Kentwell Hall, Long Melford, Suffolk, England

★ Aberystwyth and Portmeirion in Wales

★ Kirriemuir, Dumfries and Edinburgh in Scotland

★ Douglas, Isle of Man

★ Lisbon and Tavira in Portugal

★ California in Santa Monica

★ Los Angeles at the Griffith Observatory

★ San Francisco at the Cliff House

★ North Carolina's "Cloud Chamber for the Trees and Sky"

★ Havana in Cuba

★ Eger in Hungary

★ Cádiz in Spain

★ Great Orme at Llandudno in North Wales
There is also a portable example which Willett & Patteson tour around England and the world.

References

1. Needham, Volume 4, Part 1, 98.

Sources

★ Hill, D.R. (1993), ‘Islamic Science and Engineering’, Edinburgh University Press, page 70.

★ Lindberg, D.C. (1976), ‘Theories of Vision from Al Kindi to Kepler’, The University of Chicago Press, Chicago and London.

★ Mustapha Nazeef (1940), ‘Ibn Al-Haitham As a Naturalist Scientist’, in Arabic, published proceedings of the Memorial Gathering of Al-Hacan Ibn Al-Haitham, 21 December 1939, Egypt Printing.

★ Needham, Joseph (1986). ''Science and Civilization in China: Volume 4, Physics and Physical Technology, Part 1, Physics''. Taipei: Caves Books Ltd.

★ Omar, S.B. (1977). ‘Ibn al-Haitham's Optics’, Bibliotheca Islamica, Chicago.

See also

★ Fatal Frame

★ Hockney-Falco thesis

★ Black mirror

★ Camera lucida

★ History of cinema

★ Magic lantern

★ Optics

★ Cameras

External links

★ An Appreciation of the Camera Obscura

★ Flash Animation — Flash Animation that explains how the Camera Obscura works

★ The Camera Obscura in San Francisco — The Giant Camera of San Francisco at Ocean Beach, added to the National Register of Historic Places in 2001

★ Camera Obscura and World of Illusions, Edinburgh

★ Vermeer and the Camera Obscura by Philip Steadman

★ Paleo-camera - The camera obscura and the origins of art

★ Burns, Paul. The History of the Discovery of Cinematography An Illustrated Chronology

★ Sinden Optical Company — Camera Obscura manufacturer.

★ List of all known Camera Obscura

★ Re-opened camera obscura on Eastbourne Pier, UK

★ Willett & Patteson Camera Obscura Creators

★ Camera Obscura and Outlook Tower, Edinburgh, Scotland

★ Cameraobscuras.com George T Keene builds custom camera obscuras like the Griffith Observatory CO in Los Angeles.

★ Camera obscura in Trondheim, Norway Built by students of architecture and engineering from NTNU (The Norwegian University of Science and Technology)

★ Photo gallery and audio interview with Abelardo Morell, who creates room-size camera obscura images