Camera Obscura
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Camera obscura can also refer to analogous constructions such as a box or tent in which an exterior image is projected inside. Camera obscuras with a lens in the opening have been used since the second half of the 16th century and became popular as aids for drawing and painting. The concept was developed further into the photographic camera in the first half of the 19th century, when camera obscura boxes were used to expose light-sensitive materials to the projected image.
The camera obscura was used to study eclipses without the risk of damaging the eyes by looking directly into the sun. As a drawing aid, it allowed tracing the projected image to produce a highly accurate representation, and was especially appreciated as an easy way to achieve proper graphical perspective.
Before the term camera obscura was first used in 1604, other terms were used to refer to the devices: cubiculum obscurum, cubiculum tenebricosum, conclave obscurum, and locus obscurus.[5]
A camera obscura without a lens but with a very small hole is sometimes referred to as a pinhole camera, although this more often refers to simple (homemade) lensless cameras where photographic film or photographic paper is used.
The human eye (and those of animals such as birds, fish, reptiles etc.) works much like a camera obscura with an opening (pupil), a convex lens, and a surface where the image is formed (retina). Some cameras obscura use a concave mirror for a focusing effect similar to a convex lens.[6]
A camera obscura consists of a box, tent, or room with a small hole in one side or the top. Light from an external scene passes through the hole and strikes a surface inside, where the scene is reproduced, inverted (upside-down) and reversed (left to right), but with color and perspective preserved.[7]
The box-type camera obscura often has an angled mirror projecting an upright image onto tracing paper placed on its glass top. Although the image is viewed from the back, it is reversed by the mirror.[9]
There are theories that occurrences of camera obscura effects (through tiny holes in tents or in screens of animal hide) inspired paleolithic cave paintings. Distortions in the shapes of animals in many paleolithic cave artworks might be inspired by distortions seen when the surface on which an image was projected was not straight or not in the right angle.[10]It is also suggested that camera obscura projections could have played a role in Neolithic structures.[11][12]
One of the earliest known written records of a pinhole camera for camera obscura effect is found in the Chinese text called Mozi, dated to the 4th century BC, traditionally ascribed to and named for Mozi (circa 470 BC-circa 391 BC), a Chinese philosopher and the founder of Mohist School of Logic.[15] These writings explain how the image in a "collecting-point" or "treasure house"[note 1] is inverted by an intersecting point (pinhole) that collects the (rays of) light. Light coming from the foot of an illuminated person were partly hidden below (i.e., strike below the pinhole) and partly formed the top of the image. Rays from the head were partly hidden above (i.e., strike above the pinhole) and partly formed the lower part of the image.[16][17]
In his book Optics (circa 300 BC, surviving in later manuscripts from around 1000 AD), Euclid proposed mathematical descriptions of vision with "lines drawn directly from the eye pass through a space of great extent" and "the form of the space included in our vision is a cone, with its apex in the eye and its base at the limits of our vision."[18] Later versions of the text, like Ignazio Danti's 1573 annotated translation, would add a description of the camera obscura principle to demonstrate Euclid's ideas.[19]
In the 6th century, the Byzantine-Greek mathematician and architect Anthemius of Tralles (most famous as a co-architect of the Hagia Sophia) experimented with effects related to the camera obscura.[20] Anthemius had a sophisticated understanding of the involved optics, as demonstrated by a light-ray diagram he constructed in 555 AD.[21]
A picture of a three-tiered camera obscura (see illustration) has been attributed to Bacon,[33] but the source for this attribution is not given. A very similar picture is found in Athanasius Kircher's Ars Magna Lucis et Umbrae (1646).[34]
French astronomer Guillaume de Saint-Cloud suggested in his 1292 work Almanach Planetarum that the eccentricity of the sun could be determined with the camera obscura from the inverse proportion between the distances and the apparent solar diameters at apogee and perigee.[38]
Da Vinci was clearly very interested in the camera obscura: over the years he drew circa 270 diagrams of the camera obscura in his notebooks . He systematically experimented with various shapes and sizes of apertures and with multiple apertures (1, 2, 3, 4, 8, 16, 24, 28 and 32). He compared the working of the eye to that of the camera obscura and seemed especially interested in its capability of demonstrating basic principles of optics: the inversion of images through the pinhole or pupil, the non-interference of images and the fact that images are "all in all and all in every part".[46]
Italian polymath Giambattista della Porta described the camera obscura, which he called "obscurum cubiculum", in the 1558 first edition of his book series Magia Naturalis. He suggested to use a convex lens to project the image onto paper and to use this as a drawing aid. Della Porta compared the human eye to the camera obscura: "For the image is let into the eye through the eyeball just as here through the window". The popularity of Della Porta's books helped spread knowledge of the camera obscura.[49][50]
In his 1567 work La Pratica della Perspettiva Venetian nobleman Daniele Barbaro (1513-1570) described using a camera obscura with a biconvex lens as a drawing aid and points out that the picture is more vivid if the lens is covered as much as to leave a circumference in the middle.[47]
In his influential and meticulously annotated Latin edition of the works of Ibn al-Haytham and Witelo, Opticae thesauru (1572), German mathematician Friedrich Risner proposed a portable camera obscura drawing aid; a lightweight wooden hut with lenses in each of its four walls that would project images of the surroundings on a paper cube in the middle. The construction could be carried on two wooden poles.[51] A very similar setup was illustrated in 1645 in Athanasius Kircher's influential book Ars Magna Lucis Et Umbrae.[52]
Around 1575 Italian Dominican priest, mathematician, astronomer, and cosmographer Ignazio Danti designed a camera obscura gnomon and a meridian line for the Basilica of Santa Maria Novella, Florence and he later had a massive gnomon built in the San Petronio Basilica in Bologna. The gnomon was used to study the movements of the sun during the year and helped in determining the new Gregorian calendar for which Danti took place in the commission appointed by Pope Gregorius XIII and instituted in 1582.[53]
In his 1585 book Diversarum Speculationum Mathematicarum[54] Venetian mathematician Giambattista Benedetti proposed to use a mirror in a 45-degree angle to project the image upright. This leaves the image reversed, but would become common practice in later camera obscura boxes.[47]
Giambattista della Porta added a "lenticular crystal" or biconvex lens to the camera obscura description in the 1589 second edition of Magia Naturalis. He also described use of the camera obscura to project hunting scenes, banquets, battles, plays, or anything desired on white sheets. Trees, forests, rivers, mountains "that are really so, or made by Art, of Wood, or some other matter" could be arranged on a plain in the sunshine on the other side of the camera obscura wall. Little children and animals (for instance handmade deer, wild boars, rhinos, elephants, and lions) could perform in this set. "Then, by degrees, they must appear, as coming out of their dens, upon the Plain: The Hunter he must come with his hunting Pole, Nets, Arrows, and other necessaries, that may represent hunting: Let there be Horns, Cornets, Trumpets sounded: those that are in the Chamber shall see Trees, Animals, Hunters Faces, and all the rest so plainly, that they cannot tell whether they be true or delusions: Swords drawn will glister in at the hole, that they will make people almost afraid." Della Porta claimed to have shown such spectacles often to his friends. They admired it very much and could hardly be convinced by Della Porta's explanations that what they had seen was really an optical trick.[49][55][56]
The earliest use of the term "camera obscura" is found in the 1604 book Ad Vitellionem Paralipomena by German mathematician, astronomer, and astrologer Johannes Kepler.[57] Kepler discovered the working of the camera obscura by recreating its principle with a book replacing a shining body and sending threads from its edges through a many-cornered aperture in a table onto the floor where the threads recreated the shape of the book. He also realized that images are "painted" inverted and reversed on the retina of the eye and figured that this is somehow corrected by the brain.[58] In 1607, Kepler studied the sun in his camera obscura and noticed a sunspot, but he thought it was Mercury transiting the sun.[59]In his 1611 book Dioptrice, Kepler described how the projected image of the camera obscura can be improved and reverted with a lens. It is believed he later used a telescope with three lenses to revert the image in the camera obscura.[47]
In 1611, Frisian/German astronomers David and Johannes Fabricius (father and son) studied sunspots with a camera obscura, after realizing looking at the sun directly with the telescope could damage their eyes.[59] They are thought to have combined the telescope and the camera obscura into camera obscura telescopy.[59][60] 781b155fdc