Camera obscura


Camera obscura, also referred to as pinhole image, is the natural optical phenomenon that occurs when an image of a scene at the other side of a screen is projected through a small hole in that screen as a reversed and inverted image on a surface opposite to the opening. The surroundings of the projected image have to be relatively dark for the image to be clear, so many historical camera obscura experiments were performed in dark rooms.
The term "camera obscura" also refers to constructions or devices that make use of the principle within a box, tent, or room. Camera obscuras with a lens in the opening have been used since the second half of the 16th century and became popular as an aid for drawing and painting. The camera obscura box 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 as a means to study eclipses without the risk of damaging the eyes by looking into the sun directly. As a drawing aid, the camera obscura allowed tracing the projected image to produce a highly accurate representation, especially appreciated as an easy way to achieve a proper graphical perspective.
Before the term "camera obscura" was first used in 1604, many others are attested: "cubiculum obscurum", "cubiculum tenebricosum", "conclave obscurum" and "locus obscurus".
A camera obscura device without a lens but with a very small hole is sometimes referred to as a "pinhole camera", although this more often refers to simple lens-less cameras in which photographic film or photographic paper is used.

Physical explanation

Rays of light travel in straight lines and change when they are reflected and partly absorbed by an object, retaining information about the color and brightness of the surface of that object. Lit objects reflect rays of light in all directions. A small enough opening in a screen only lets through rays that travel directly from different points in the scene on the other side, and these rays form an image of that scene when they are collected on a surface opposite from the opening.
The human eye works much like a camera obscura with an opening, a biconvex lens and a surface where the image is formed.

Technology

A camera obscura device consists of a box, tent, or room with a small hole in one side. Light from an external scene passes through the hole and strikes a surface inside, where the scene is reproduced, inverted, and reversed, but with color and perspective preserved.
In order to produce a reasonably clear projected image, the aperture has to be about 1/100th the distance to the screen, or less.
As the pinhole is made smaller, the image gets sharper, but the projected image becomes dimmer. With too small a pinhole, however, the sharpness worsens, due to diffraction.
In practice, camera obscuras use a lens rather than a pinhole because it allows a larger aperture, giving a usable brightness while maintaining focus.
If the image is caught on a semi-transparent screen, it can be viewed from the back so that it is no longer reversed.
Using mirrors it is possible to project a right-side-up image. The projection can also be diverted onto a horizontal surface. The 18th-century overhead version in tents used mirrors inside a kind of periscope on the top of the tent.
The box-type camera obscura often has an angled mirror projecting an upright image onto tracing paper placed on the glass top. Although the image is viewed from the back, it is now reversed by the mirror.

History

Prehistory to 500 BCE: Possible inspiration for prehistoric art and possible use in religious ceremonies, gnomons

There are theories that occurrences of camera obscura effects 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.
It is also suggested that camera obscura projections could have played a role in Neolithic structures.
during the solstice on 21 June 2012
Perforated gnomons projecting a pinhole image of the sun were described in the Chinese Zhoubi Suanjing writings. The location of the bright circle can be measured to tell the time of day and year. In Arab and European cultures its invention was much later attributed to Egyptian astronomer and mathematician Ibn Yunus around 1000 CE.
Some ancient sightings of gods and spirits, especially in temple worship, are thought to possibly have been conjured up by means of camera obscura projections.

500 BCE to 500 CE: Earliest written observations

The earliest known written record of the camera obscura is found in the Chinese text called Mozi, dated to the 4th century BCE, traditionally ascribed to and named for Mozi, a Han Chinese philosopher and the founder of Mohist School of Logic. These writings explain how the image in a "collecting-point" or "treasure house" is inverted by an intersecting point that collects the light. Light coming from the foot of an illuminated person would partly be hidden below and partly form the top part of the image. Rays from the head would partly be hidden above and partly form the lower part of the image. This is a remarkably early correct description of the camera obscura; there are no other examples known that are dated before the 11th century.
The Greek philosopher Aristotle, or possibly a follower of his ideas, touched upon the subject in the work Problems – Book XV, asking: and further on:
Many philosophers and scientists of the Western world would ponder this question before it became accepted that the circular and crescent-shapes described in this "problem" were actually pinhole image projections of the sun. Although a projected image will have the shape of the aperture when the light source, aperture and projection plane are close together, the projected image will have the shape of the light source when they are further apart.
In his book Optics, 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." 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.

500 to 1000: Earliest experiments, study of light

In the 6th century, the Byzantine-Greek mathematician and architect Anthemius of Tralles experimented with effects related to the camera obscura. Anthemius had a sophisticated understanding of the involved optics, as demonstrated by a light-ray diagram he constructed in 555 CE.
In the 10th century Yu Chao-Lung supposedly projected images of pagoda models through a small hole onto a screen to study directions and divergence of rays of light.

1000 to 1400: Optical and astronomical tool, entertainment

extensively studied the camera obscura phenomenon in the early 11th century. He provided the first competent geometrical and quantitative descriptions of the phenomenon and must have understood the relationship between the focal point and the pinhole,
In his Book of Optics, Ibn al-Haytham explained that rays of light travel in straight lines and are distinguished by the body that reflected the rays, and then wrote:
He described a "dark chamber" and did a number of trials of experiments with small pinholes and light passing through them. This experiment consisted of three candles in a row and seeing the effects on the wall after placing a cutout between the candles and the wall.
Ibn al-Haytham also analyzed the rays of sunlight and concluded that they make a conic shape where they meet at the hole, forming another conic shape reverse to the first one from the hole to the opposite wall in the dark room. Ibn al-Haytham's writings on optics became very influential in Europe through Latin translations since circa 1200. Among those he inspired were Witelo, John Peckham, Roger Bacon, Leonardo Da Vinci, René Descartes and Johannes Kepler.
In his 1088 book, Dream Pool Essays, the Song Dynasty Chinese scientist Shen Kuo compared the focal point of a concave burning-mirror and the "collecting" hole of camera obscura phenomena to an oar in a rowlock to explain how the images were inverted:
Shen Kuo also responded to a statement of Duan Chengshi in Miscellaneous Morsels from Youyang written in about 840 that the inverted image of a Chinese pagoda tower beside a seashore, was inverted because it was reflected by the sea: "This is nonsense. It is a normal principle that the image is inverted after passing through the small hole."
English statesman and scholastic philosopher Robert Grosseteste was one of the earliest Europeans who commented on the camera obscura.
English philosopher and Franciscan friar Roger Bacon falsely stated in his De Multiplicatione Specerium that an image projected through a square aperture was round because light would travel in spherical waves and therefore assumed its natural shape after passing through a hole. He is also credited with a manuscript that advised to study solar eclipses safely by observing the rays passing through some round hole and studying the spot of light they form on a surface.
A picture of a three-tiered camera obscura has been attributed to Bacon, but the source for this attribution is not given. A very similar picture is found in Athanasius Kircher's Ars Magna Lucis et Umbrae.
Polish friar, theologian, physicist, mathematician and natural philosopher Erazmus Ciołek Witelo wrote about the camera obscura in his very influential treatise Perspectiva, which was largely based on Ibn al-Haytham's work.
English archbishop and scholar John Peckham wrote about the camera obscura in his Tractatus de Perspectiva and Perspectiva communis, falsely arguing that light gradually forms the circular shape after passing through the aperture. His writings were influenced by Roger Bacon.
At the end of the 13th century, Arnaldus de Villa Nova is credited with using a camera obscura to project live performances for entertainment.
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.
Kamāl al-Dīn al-Fārisī described in his 1309 work Kitab Tanqih al-Manazir how he experimented with a glass sphere filled with water in a camera obscura with a controlled aperture and found that the colors of the rainbow are phenomena of the decomposition of light.
French Jewish philosopher, mathematician, physicist and astronomer/astrologer Levi ben Gershon made several astronomical observations using a camera obscura with a Jacob's staff, describing methods to measure the angular diameters of the sun, the moon and the bright planets Venus and Jupiter. He determined the eccentricity of the sun based on his observations of the summer and winter solstices in 1334. Levi also noted how the size of the aperture determined the size of the projected image. He wrote about his findings in Hebrew in his treatise Sefer Milhamot Ha-Shem Book V Chapters 5 and 9.

1450 to 1600: Depiction, lenses, drawing aid, mirrors

Italian polymath Leonardo da Vinci, familiar with the work of Alhazen in Latin translation, and after an extensive study of optics and human vision, wrote the oldest known clear description of the camera obscura in mirror writing in a notebook in 1502, later published in the collection Codex Atlanticus :
These descriptions, however, would remain unknown until Venturi deciphered and published them in 1797.
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. 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".
The oldest known published drawing of a camera obscura is found in Dutch physician, mathematician and instrument maker Gemma Frisius’ 1545 book De Radio Astronomica et Geometrica, in which he described and illustrated how he used the camera obscura to study the solar eclipse of 24 January 1544
Italian polymath Gerolamo Cardano described using a glass disc – probably a biconvex lens – in a camera obscura in his 1550 book De subtilitate, vol. I, Libri IV. He suggested to use it to view "what takes place in the street when the sun shines" and advised to use a very white sheet of paper as a projection screen so the colours wouldn't be dull.
Sicilian mathematician and astronomer Francesco Maurolico answered Aristotle's problem how sunlight that shines through rectangular holes can form round spots of light or crescent-shaped spots during an eclipse in his treatise Photismi de lumine et umbra. However this wasn't published before 1611, after Johannes Kepler had published similar findings of his own.
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 mirror 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.
In his 1567 work La Pratica della Perspettiva Venetian nobleman Daniele Barbaro 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.
In his influential and meticulously annotated Latin edition of the works of Ibn al-Haytham and Witelo Opticae thesauru 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. A very similar setup was illustrated in 1645 in Athanasius Kircher's influential book Ars Magna Lucis Et Umbrae.
Around 1575 Italian Dominican priest, mathematician, astronomer, and cosmographer Ignazio Danti designed a camera obscura gnomom 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.
In his 1585 book Diversarum Speculationum Mathematicarum 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.
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 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.

1600 to 1650: Name coined, camera obscura telescopy, portable drawing aid in tents and boxes

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. 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.
In 1607, Kepler studied the sun in his camera obscura and noticed a sunspot, but he thought it was Mercury transiting the sun.
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.
In 1611, Frisian/German astronomers David and Johannes Fabricius studied sunspots with a camera obscura, after realizing looking at the sun directly with the telescope could damage their eyes. They are thought to have combined the telescope and the camera obscura into camera obscura telescopy.
In 1612, Italian mathematician Benedetto Castelli wrote to his mentor, the Italian astronomer, physicist, engineer, philosopher, and mathematician Galileo Galilei about projecting images of the sun through a telescope to study the recently discovered sunspots. Galilei wrote about Castelli's technique to the German Jesuit priest, physicist, and astronomer Christoph Scheiner.
From 1612 to at least 1630, Christoph Scheiner would keep on studying sunspots and constructing new telescopic solar-projection systems. He called these "Heliotropii Telioscopici", later contracted to helioscope. For his helioscope studies, Scheiner built a box around the viewing/projecting end of the telescope, which can be seen as the oldest known version of a box-type camera obscura. Scheiner also made a portable camera obscura.
In his 1613 book Opticorum Libri Sex Belgian Jesuit mathematician, physicist, and architect François d'Aguilon described how some charlatans cheated people out of their money by claiming they knew necromancy and would raise the specters of the devil from hell to show them to the audience inside a dark room. The image of an assistant with a devil's mask was projected through a lens into the dark room, scaring the uneducated spectators.
By 1620 Kepler used a portable camera obscura tent with a modified telescope to draw landscapes. It could be turned around to capture the surroundings in parts.
Dutch inventor Cornelis Drebbel is thought to have constructed a box-type camera obscura which corrected the inversion of the projected image. In 1622, he sold one to the Dutch poet, composer, and diplomat Constantijn Huygens who used it to paint and recommended it to his artist friends. Huygens wrote to his parents :
German Orientalist, mathematician, inventor, poet, and librarian Daniel Schwenter wrote in his 1636 book Deliciae Physico-Mathematicae about an instrument that a man from Pappenheim had shown him, which enabled movement of a lens to project more from a scene through the camera obscura. It consisted of a ball as big as a fist, through which a hole was made with a lens attached on one side. This ball was placed inside two-halves of part of a hollow ball that were then glued together, in which it could be turned around. This device was attached to a wall of the camera obscura. This universal joint mechanism was later called a scioptric ball.
In his 1637 book Dioptrique French philosopher, mathematician and scientist René Descartes suggested placing an eye of a recently dead man into an opening in a darkened room and scraping away the flesh at the back until one could see the inverted image formed on the retina.
Italian Jesuit philosopher, mathematician, and astronomer Mario Bettini wrote about making a camera obscura with twelve holes in his Apiaria universae philosophiae mathematicae. When a foot soldier would stand in front of the camera, a twelve-person army of soldiers making the same movements would be projected.
French mathematician, Minim friar, and painter of anamorphic art Jean-François Nicéron wrote about the camera obscura with convex lenses. He explained how the camera obscura could be used by painters to achieve perfect perspective in their work. He also complained how charlatans abused the camera obscura to fool witless spectators and make them believe that the projections were magic or occult science. These writings were published in a posthumous version of La Perspective Curieuse.

1650 to 1800: Introduction of the magic lantern, popular portable box-type drawing aid, painting aid

The use of the camera obscura to project special shows to entertain an audience seems to have remained very rare. A description of what was most likely such a show in 1656 in France, was penned by the poet Jean Loret. The Parisian society were presented with upside-down images of palaces, ballet dancing and battling with swords. The performance was silent and Loret was surprised that all the movements made no sound. Loret felt somewhat frustrated that he did not know the secret that made this spectacle possible. There are several clues that this was a camera obscura show, rather than a very early magic lantern show, especially in the upside-down image and the energetic movements.
German Jesuit scientist Gaspar Schott heard from a traveler about a small camera obscura device he had seen in Spain, which one could carry under one arm and could be hidden under a coat. He then constructed his own sliding box camera obscura, which could focus by sliding a wooden box part fitted inside another wooden box part. He wrote about this in his 1657 Magia universalis naturæ et artis.
By 1659 the magic lantern was introduced and partly replaced the camera obscura as a projection device, while the camera obscura mostly remained popular as a drawing aid. The magic lantern can be seen as a development of the camera obscura device.
The 17th century Dutch Masters, such as Johannes Vermeer, were known for their magnificent attention to detail. It has been widely speculated that they made use of the camera obscura, but the extent of their use by artists at this period remains a matter of fierce contention, recently revived by the Hockney–Falco thesis.
, Collegium Experimentale
German philosopher Johann Sturm published an illustrated article about the construction of a portable camera obscura box with a 45° mirror and an oiled paper screen in the first volume of the proceedings of the Collegium Curiosum, Collegium Experimentale, sive Curiosum.
Johann Zahn's Oculus Artificialis Teledioptricus Sive Telescopium, published in 1685, contains many descriptions, diagrams, illustrations and sketches of both the camera obscura and the magic lantern. A hand-held device with a mirror-reflex mechanism was first proposed by Johann Zahn in 1685, a design that would later be used in photographic cameras.
The scientist Robert Hooke presented a paper in 1694 to the Royal Society, in which he described a portable camera obscura. It was a cone-shaped box which fit onto the head and shoulders of its user.
From the beginning of the 18th century, craftsmen and opticians would make camera obscura devices in the shape of books, which were much appreciated by lovers of optical devices.
One chapter in the Conte Algarotti's Saggio sopra Pittura is dedicated to the use of a camera ottica in painting.
By the 18th century, following developments by Robert Boyle and Robert Hooke, more easily portable models in boxes became available. These were extensively used by amateur artists while on their travels, but they were also employed by professionals, including Paul Sandby and Joshua Reynolds, whose camera is now in the Science Museum in London. Such cameras were later adapted by Joseph Nicephore Niepce, Louis Daguerre and William Fox Talbot for creating the first photographs.

Role in the modern age

While the technical principles of the camera obscura have been known since antiquity, the broad use of the technical concept in producing images with a linear perspective in paintings, maps, theatre setups, and architectural, and, later, photographic images and movies started in the Western Renaissance and the scientific revolution. While, e.g., Alhazen had already observed an optical effect and developed a state of the art theory of the refraction of light, he was less interested to produce images with it ; the society he lived in was even hostile towards personal images. Western artists and philosophers used the Arab findings in new frameworks of epistemic relevance. E.g. Leonardo da Vinci used the camera obscura as a model of the eye, René Descartes for eye and mind and John Locke started to use the camera obscura as a metaphor of human understanding per se. The modern use of the camera obscura as an epistemic machine had important side effects for science. While the use of the camera obscura has dwindled, for those who are interested in making one it only requires a few items including: a box, tracing paper, tape, foil, a box cutter, a pencil and a blanket to keep out the light.
In 1827, critic Vergnaud complained about the use of camera obscura for many painting at that year's Salon exhibition in Paris: "Is the public to blame, the artists, or the jury, when history paintings, already rare, are sacrificed to genre painting, and what genre at that!... that of the camera obscura."

Examples

Public access

Cultural references