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Posted 10:00 am, May 11, 2008, by sagayago |
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A pinhole camera is a camera without a glass lens. An extremely small hole in a very thin material can focus light by confining all rays from a scene through a single point. In order to produce a reasonably clear image, the ratio of the aperture to the distance to the screen should be 1/100 or less. The shutter of a pinhole camera usually consists of a hand operated flap of some light-proof material to cover and uncover the pinhole.
A common use of a pinhole camera is to capture the movement of sunlight over a long period of time. This type of photography is called Solargraphy. Pinhole cameras require much longer exposure times than conventional cameras because of the small aperture; typical exposure times can range from 5 seconds to hours or days.
The image may be projected on a translucent screen for real-time viewing (popular for viewing solar eclipses; see also camera obscura), or can expose film or a charge coupled device (CCD). Pinhole cameras with CCDs are sometimes used for surveillance work because of their small size.
Invention of pinhole camera
As far back as 500 B.C., Greeks such as Aristotle and Euclid wrote on naturally-occurring rudimentary pinhole cameras. For example, light may travel through the slits of wicker baskets or the crossing of tree leaves. The ancient Greeks, however, believed that vision is enabled by rays emitted from the eye. The discovery that vision results from rays entering the eye rather than being emitted by it enabled a much better understanding of the pinhole camera effect. It was the 10th-century Muslim mathematician, astronomer and physicist Ibn al-Haytham who published this idea. He also invented the first pinhole camera after noticing the way light was streaming through a hole in a window shutter. He improved on the camera after realizing that the smaller the pinhole, the sharper the image (though the less light). He designed the first camera obscura (Lat. dark chamber). As a side benefit of his invention, he was credited with being first man to shift physics from a philosophical to an experimental basis.
In the 5th century BC, the Mohist philosopher Mo Jing (墨經) in ancient China mentioned the effect of an "image forming through a pinhole". Along with experimenting with the pinhole camera and the burning mirror of the ancient Mohists, the Song Dynasty (960-1279 AD) Chinese scientist Shen Kuo (1031-1095) experimented with camera obscura and was the first to establish geometrical and quantitative attributes for it. In the 13th century , Robert Grosseteste and Roger Bacon commented on the pinhole camera. Between 1000 and 1600, men such as Ibn al-Haytham, Gemma Frisius, and Giambattista della Porta wrote on the pinhole camera, explaining why the images are upside down. Pinhole devices provide safety in viewing solar eclipses because the observer views the diminished intensity of the pinhole image rather than the full light of the eclipse itself.
wikipedia
pinhole cameras in Flickr
Pinhole camera
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