Camera obscura Totally Explained

Everything about The Camera Obscura totally explained

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 accurate, 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 below), it's 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.

Discovery and origins

   The first mention and discovery of the principles behind the pinhole camera, a precursor to the camera obscura, belong to Mo-Ti (470 BC to 390 BC), a Chinese philosopher and founder of Mohism. Other observations made by Mozi and his followers include Newton's first law of motion. The Mohist tradition is also highly unusual in Chinese thought in that it devoted time to developing principles of logic. Further down the line, Aristotle (384 to 322 BC) understood the optical principle of the pinhole camera. He viewed the crescent shape of a partially eclipsed sun projected on the ground through the holes in a sieve, and the gaps between leaves of a plane tree.
   The first camera obscura was later built by an Iraqi scientist named Abu Ali Al-Hasan Ibn al-Haitham, born in Basra (965-1039 AD), known in the West as Alhacen or Alhazen, who carried out practical experiments on optics in his Book of Optics. 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's 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's 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's 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 don't 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 both the pinhole camera and camera obscura is credited to Ibn al-Haytham, the camera obscura was first described by Aristotle, who was the first to describe how an image is formed on the eye, using the camera obscura as an analogy. Alhazen states (in the Latin translation), and with respect to the camera obscura, "Et nos non inventimus ita", we didn't invent this. Several decades after Ibn al-Haitham's death, the Song Dynasty Chinese scientist Shen Kuo (1031-1095) 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. 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. 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:

Turin in Italy- at the Cinema Museum inside the Mole Antonelliana by Antonelli.
Edinburgh in Scotland - See the Camera Obscura site
Grahamstown in South Africa
Johannesburg in South Africa
Pretoria in South Africa
Cape Town 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
Dumfries Museum and Camera Obscura, Scotland
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 in the Torre Tavira
Great Orme at Llandudno in North Wales
Royal Observatory, Greenwich, London
Perdika, Aegina Island, Greece.
Marburg, Universitie of Physik, Germany There is also a portable example which Willett & Patteson tour around England and the world.

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