Camera obscura

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The camera obscura (Latin; "camera" is a "vaulted chamber/room" + "obscura" means "dark"= "darkened chamber/room") is an optical device that projects an image of its surroundings on a screen. It is used in drawing and for entertainment, and was one of the inventions that led to photography. The device consists of a box or room with a hole in one side. Light from an external scene passes through the hole and strikes a surface inside where it is reproduced, upside-down, but with colour and perspective preserved. The image can be projected onto paper, and can then be traced to produce a highly accurate representation.

Using mirrors, as in the 18th century overhead version (illustrated in the Discovery and Origins section below), it is possible to project a right-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 being upright as viewed from the back.

As a pinhole is made smaller, the image gets sharper, but the projected image becomes dimmer. With too small a pinhole the sharpness again becomes worse due to diffraction. Some practical camera obscuras use a lens rather than a pinhole because it allows a larger aperture, giving a usable brightness while maintaining focus. (See pinhole camera for construction information.)


Discovery and origins

The first mention of the principles behind the pinhole camera, a precursor to the camera obscura, belongs to Mo-Ti (470 BCE to 390 BCE), a Chinese philosopher and the founder of Mohism.[1] Mo-Ti referred to this camera as a "collecting plate" or "locked treasure room".[2] The Mohist tradition is unusual in Chinese thought because it is concerned with developing principles of logic. The Greek philosopher Aristotle (384 to 322 BCE) 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.

In the 6th century, Byzantine mathematician and architect Anthemius of Tralles (most famous for designing the Hagia Sophia), used a type of camera obscura in his experiments.[3]

However, it was mastered by the scientist Abu Ali Al-Hasan Ibn al-Haytham, 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.[4][verification needed]

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