For other uses, see Camera (disambiguation).
A camera is an optical instrument that records images that can be stored directly, transmitted to another location, or both. These images may be still photographs or moving images such as videos or movies. The term camera comes from the word camera obscura (Latin for "dark chamber"), an early mechanism for projecting images. The modern camera evolved from the camera obscura.
1 Functional description,
3.1 Image capture,
3.4 Exposure control,
4 Film formats,
5 Camera accessories,
6 Camera designs
6.1 Plate camera,
6.2 Large-format camera,
6.3 Medium-format camera,
6.4 Folding camera,
6.5 Box camera,
6.6 Rangefinder camera,
6.7 Single-lens reflex,
6.8 Twin-lens reflex,
6.9 Subminiature camera,
6.10 Instant picture camera,
6.11 Ciné camera,
7 See also
10 External links,
A camera may work with the light of the visible spectrum or with other portions of the electromagnetic spectrum A still camera is an optical device which creates a single image of an object or scene, and records it on an electronic sensor or photographic film. All cameras utilize the same basic design: light enters an enclosed box through a converging lens and an image is recorded on a light-sensitive medium. A shutter mechanism controls the length of time that light can enter the camera. Most photographic cameras have functions which allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, and to control the exposure so that it is not too bright or too dim. A data display, often a liquid crystal display (LCD), permits the user to view settings such as film speed, exposure, and shutter speed.
A film or video camera operates similarly to a still camera, except it records a series of static images in rapid succession, commonly at a rate of 24 frames per second. When the images are combined and displayed in order, the illusion of motion of achieved.
Main article: http://en.wikipedia.org/wiki/History_of_the_camera
The forerunner to the photographic camera was the camera obscura. In the fifth century B.C., the Chinese philosopher Mo Ti noted that a pinhole can form an inverted and focused image, when light passes through the hole and into a dark area. Mo Ti is the first recorded person to have exploited this phenomenon to trace the inverted image to create a picture. Writing in the fourth century B.C., Aristotle also mentioned this principle. He described observing a partial solar eclipse in 330 B.C. by seeing the image of the Sun projected through the small spaces between the leaves of a tree. In the tenth century, the Arabic scholar Ibn al-Haytham (Alhazen) also wrote about observing a solar eclipse through a pinhole, and he described how a sharper image could be produced by making the opening of the pinhole smaller.English philosopher Roger Bacon wrote about these optical principles in his 1267 treatise Perspectiva. By the fifteenth century, artists and scientists were using this phenomenon to make observations. Originally, an observer had to enter an actual room, in a which a pinhole was made on one wall. On the opposite wall, the observer would view the inverted image of the outside. The name camera obscura, Latin for "dark room", derives from this early implementation of the optical phenomenon. The term was first coined by mathematician and astronomer Johannes Kepler in his Ad Vitellionem paralipomena of 1604.
The Italian scientist Giambattista della Porta described the camera obscura in detail in his 1558 work Magia Naturalis, and specifically suggested that an artist could project a camera obscura's images onto paper, and trace the outlines. The camera obscura was popular as an aid for drawing and painting from the 1600s to the 1800s. Portable set-ups were devised in the 17th century. For example, Kepler had built a portable tent, and outfitted the camera obscura with a lens by 1620. This set-up remained popular up to the early 1800s. 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. A hand-held device with a mirror reflex mechanism was first proposed by Johann Zahn in 1685, a design that would later be utilized in photographic cameras.
Before the development of the photographic camera, it had been known for hundreds of years that some substances, such as silver salts, darkened when exposed to sunlight. In a series of experiments, published in 1727, the German scientist Johann Heinrich Schulze demonstrated that the darkening of the salts was due to light alone, and not influenced by heat or exposure to air. The Swedish chemist Carl Wilhelm Scheele showed in 1777 that silver chloride was especially susceptible to darkening from light exposure, and that once darkened, it becomes insoluble in an ammonia solution. The first person to utilize this chemistry to create images was Thomas Wedgwood. To create images, Wedgwood placed items, such as leaves and insect wings, on ceramic pots coated with silver nitrate, and exposed the set-up to light. These images weren't permanent, however, as Wedgwood didn't employ a fixing mechanism. He ultimately failed at his goal of using the process to create fixed images created by a camera obscura.
The first permanent photograph of a camera image was made in 1826 by Joseph Nicéphore Niépce using a sliding wooden box camera made by Charles and Vincent Chevalier in Paris. Niépce had been experimenting with ways to fix the images of a camera obscura since 1816. The photograph Niépce succeeded in creating shows the view from his window. It was made using an 8-hour exposure on pewter coated with bitumen. Niépce called his process "heliography". Niépce corresponded with the inventor Louis-Jacques-Mande Daguerre, and the pair entered into a partnership to improve the heliographic process. Niépce had experimented further with other chemicals, to improve contrast in his heliographs. Daguerre contributed an improved camera obscura design, but the partnership ended when Niépce died in 1833. Daguerre succeeded in developing a high-contrast and extremely sharp image by exposing on a plate coated with silver iodide, and exposing this plate again to mercury vapor. By 1837, he was able to fix the images with a common salt solution. He called this process Daguerreotypie, and tried unsuccessfully for a couple years to commercialize it. Eventually, with help of the scientist and politician François Arago, the French government acquired Daguerre's process for public release. In exchange, pensions were provided to Daguerre and Niépce's son, Isidore.
The first photographic camera developed for commercial manufacture was a daguerreotype camera, built by Alphonse Giroux. Giroux signed a contact with Daguerre and Isidore Niépce to produce the cameras in France, which each device and accessories costing 400 francs. The camera was a double-box design, with a landscape lens fitted to the outer box, and a holder for a ground glass focusing screen and image plate on the inner box. By sliding the inner box, objects at various distances could be brought to as sharp a focus as desired. After a satisfactory image had been focused on the screen, the screen was replaced with a sensitized plate. A knurled wheel controlled a copper flap in front of the lens, which functioned as a shutter. The early daguerreotype cameras required long exposure times, which in 1839 could be from 5 to 30 minutes.
Similar cameras were used for exposing the silver-surfaced copper plates, commercially introduced in 1839, which were the first practical photographic medium. The collodion wet plate process that gradually replaced the daguerreotype during the 1850s required photographers to coat and sensitize thin glass or iron plates shortly before use and expose them in the camera while still wet. Early wet plate cameras were very simple and little different from Daguerreotype cameras, but more sophisticated designs eventually appeared. The Dubroni of 1864 allowed the sensitizing and developing of the plates to be carried out inside the camera itself rather than in a separate darkroom. Other cameras were fitted with multiple lenses for photographing several small portraits on a single larger plate, useful when making cartes de visite. It was during the wet plate era that the use of bellows for focusing became widespread, making the bulkier and less easily adjusted nested box design obsolete.
For many years, exposure times were long enough that the photographer simply removed the lens cap, counted off the number of seconds (or minutes) estimated to be required by the lighting conditions, then replaced the cap. As more sensitive photographic materials became available, cameras began to incorporate mechanical shutter mechanisms that allowed very short and accurately timed exposures to be made.
The electronic video camera tube was invented in the 1920s, starting a line of development that eventually resulted in digital cameras, which largely supplanted film cameras around the start of the 21st century.
Traditional cameras capture light onto photographic film or photographic plate. Video and digital cameras use an electronic image sensor, usually a charge coupled device (CCD) or a CMOS sensor to capture images which can be transferred or stored in a memory card or other storage inside the camera for later playback or processing.
Cameras that capture many images in sequence are known as movie cameras or as ciné cameras in Europe; those designed for single images are still cameras.
However these categories overlap as still cameras are often used to capture moving images in special effects work and many modern cameras can quickly switch between still and motion recording modes.
A video camera is a category of movie camera that captures images electronically (either using analog or digital technology).
The lens of a camera captures the light from the subject and brings it to a focus on the film or detector. The design and manufacture of the lens is critical to the quality of the photograph being taken. The technological revolution in camera design in the 19th century revolutionized optical glass manufacture and lens design with great benefits for modern lens manufacture in a wide range of optical instruments from reading glasses to microscopes. Pioneers included Zeiss and Leitz.
Camera lenses are made in a wide range of focal lengths. They range from extreme wide angle, wide angle, standard, medium telephoto and telephoto. Each lens is best suited a certain type of photography. The extreme wide angle may be preferred for architecture because it has the capacity to capture a wide view of a building. The normal lens, because it often has a wide aperture, is often used for street and documentary photography. The telephoto lens is useful for sports and wildlife but it is more susceptible to camera shake.
Due to the optical properties of photographic lenses, only objects within a limited range of distances from the camera will be reproduced clearly. The process of adjusting this range is known as changing the camera's focus. There are various ways of focusing a camera accurately. The simplest cameras have fixed focus and use a small aperture and wide-angle lens to ensure that everything within a certain range of distance from the lens, usually around 3 metres (10 ft) to infinity, is in reasonable focus. Fixed focus cameras are usually inexpensive types, such as single-use cameras. The camera can also have a limited focusing range or scale-focus that is indicated on the camera body. The user will guess or calculate the distance to the subject and adjust the focus accordingly. On some cameras this is indicated by symbols (head-and-shoulders; two people standing upright; one tree; mountains).
Rangefinder cameras allow the distance to objects to be measured by means of a coupled parallax unit on top of the camera, allowing the focus to be set with accuracy. Single-lens reflex cameras allow the photographer to determine the focus and composition visually using the objective lens and a moving mirror to project the image onto a ground glass or plastic micro-prism screen. Twin-lens reflex cameras use an objective lens and a focusing lens unit (usually identical to the objective lens.) in a parallel body for composition and focusing. View cameras use a ground glass screen which is removed and replaced by either a photographic plate or a reusable holder containing sheet film before exposure. Modern cameras often offer autofocus systems to focus the camera automatically by a variety of methods.
Some experimental cameras, for example the planar Fourier capture array (PFCA), do not require focusing to allow them to take pictures. In conventional digital photography, lenses or mirrors map all of the light originating from a single point of an in-focus object to a single point at the sensor plane. Each pixel thus relates an independent piece of information about the far-away scene. In contrast, a PFCA does not have a lens or mirror, but each pixel has an idiosyncratic pair of diffraction gratings above it, allowing each pixel to likewise relate an independent piece of information (specifically, one component of the 2D Fourier transform) about the far-away scene. Together, complete scene information is captured and images can be reconstructed by computation.
Some cameras have post focusing. Post focusing means take the pictures first and then focusing later at the personal computer. The camera uses many tiny lenses on the sensor to capture light from every camera angle of a scene and is called plenoptics technology. A current plenoptic camera design has 40,000 lenses working together to grab the optimal picture.
The size of the aperture and the brightness of the scene controls the amount of light that enters the camera during a period of time, and the shutter controls the length of time that the light hits the recording surface. Equivalent exposures can be made with a larger aperture and a faster shutter speed or a corresponding smaller aperture and with the shutter speed slowed down.
Main article: http://en.wikipedia.org/wiki/Shutter_(photography)
Although a range of different shutter devices have been used during the development of the camera only two types have been widely used and remain in use today.
The Leaf shutter or more precisely the in-lens shutter is a shutter contained within the lens structure, often close to the diaphragm consisting of a number of metal leaves which are maintained under spring tension and which are opened and then closed when the shutter is released. The exposure time is determined by the interval between opening and closing. In this shutter design, the whole film frame is exposed at one time. This makes flash synchronisation much simpler as the flash only needs to fire once the shutter is fully open. Disadvantages of such shutters are their inability to reliably produce very fast shutter speeds ( faster than 1/500th second or so) and the additional cost and weight of having to include a shutter mechanism for every lens.
The focal-plane shutter operates as close to the film plane as possible and consists of cloth curtains that are pulled across the film plane with a carefully determined gap between the two curtains (typically running horizontally) or consisting of a series of metal plates (typically moving vertically) just in front of the film plane. The focal-plane shutter is primarily associated with the single lens reflex type of cameras, since covering the film rather than blocking light passing through the lens allows the photographer to view through the lens at all times except during the exposure itself. Covering the film also facilitates removing the lens from a loaded camera (many SLRs have interchangeable lenses).
Professional medium format SLR (single-lens-reflex) cameras (typically using 120/220 roll film) use a hybrid solution, since such a large focal-plane shutter would be difficult to make and/or may run slowly. A manually inserted blade known as a dark slide allows the film to be covered when changing lenses or film backs. A blind inside the camera covers the film prior to and after the exposure (but is not designed to be able to give accurately controlled exposure times) and a leaf shutter that is normally open is installed in the lens. To take a picture, the leaf shutter closes, the blind opens, the leaf shutter opens then closes again, and finally the blind closes and the leaf shutter re-opens (the last step may only occur when the shutter is re-cocked).
Using a focal-plane shutter, exposing the whole film plane can take much longer than the exposure time. The exposure time does not depend on the time taken to make the exposure over all, only on the difference between the time a specific point on the film is uncovered and then covered up again. For example an exposure of 1/1000 second may be achieved by the shutter curtains moving across the film plane in 1/50th of a second but with the two curtains only separated by 1/20th of the frame width. In fact in practice the curtains do not run at a constant speed as they would in an ideal design, obtaining an even exposure time depends mainly on being able to make the two curtains accelerate in a similar manner.
When photographing rapidly moving objects, the use of a focal-plane shutter can produce some unexpected effects, since the film closest to the start position of the curtains is exposed earlier than the film closest to the end position. Typically this can result in a moving object leaving a slanting image. The direction of the slant depends on the direction the shutter curtains run in (noting also that as in all cameras the image is inverted and reversed by the lens, i.e. "top-left" is at the bottom right of the sensor as seen by a photographer behind the camera).
Focal-plane shutters are also difficult to synchronise with flash bulbs and electronic flash and it is often only possible to use flash at shutter speeds where the curtain that opens to reveal the film completes its run and the film is fully uncovered, before the second curtain starts to travel and cover it up again. Typically 35mm film SLRs could sync flash at only up to 1/60th second if the camera has horizontal run cloth curtains, and 1/125th if using a vertical run metal shutter.
Main article: http://en.wikipedia.org/wiki/Film_formats
A wide range of film and plate formats have been used by cameras. In the early history plate sizes were often specific for the make and model of camera although there quickly developed some standardisation for the more popular cameras. The introduction of roll film drove the standardization process still further so that by the 1950s only a few standard roll films were in use. These included 120 film providing 8, 12 or 16 exposures, 220 film providing 16 or 24 exposures, 127 film providing 8 or 12 exposures (principally in Brownie cameras) and 135 (35 mm film) providing 12, 20 or 36 exposures - or up to 72 exposures in the half-frame format or in bulk cassettes for the Leica Camera range.
For cine cameras, film 35 mm wide and perforated with sprocket holes was established as the standard format in the 1890s. It is still used for nearly all film-based professional motion picture production. For amateur use, several smaller and therefore less expensive formats were introduced. 17.5 mm film, created by splitting 35 mm film, was one early amateur format, but 9.5 mm film, introduced in Europe in 1922, and 16 mm film, introduced in the US in 1923, soon became the standards for "home movies" in their respective hemispheres. In 1932, the even more economical 8 mm format was created by doubling the number of perforations in 16 mm film, then splitting it, usually after exposure and processing. The Super 8 format, still 8 mm wide but with smaller perforations to make room for substantially larger film frames, was introduced in 1965.
Accessories for cameras are mainly for care, protection, special effects and functions.
Lens hood: used on the end of a lens to block the sun or other light source to prevent glare and lens flare (see also matte box).,
Lens cap: covers and protects the lens during storage.,
Lens adapter: sometimes called a step-ring, adapts the lens to other size filters.,
Lens filters: allow artificial colors or change light density.,
Lens extension tubes allow close focus in macro photography.,
Flash equipment: including light diffuser, mount and stand, reflector, soft box, trigger and cord.,
Care and protection: including camera case and cover, maintenance tools, and screen protector.,
Large format cameras use special equipment which includes magnifier loupe, view finder, angle finder, focusing rail /truck.,
Battery and sometimes a charger.,
Some professional SLR could be provided with interchangeable finders for eye-level or waist-level focusing, focusing screens, eye-cup, data backs, motor-drives for film transportation or external battery packs.,
Tripod, microscope adapter, cable release, electric wire release.,
The earliest cameras produced in significant numbers used sensitised glass plates and are now termed plate cameras. Light entered a lens mounted on a lens board which was separated from the plate by an extendible bellows.
There were simple box cameras for glass plates but also single-lens reflex cameras with interchangeable lenses and even for color photography (Autochrome Lumière).
Many of these cameras had controls to raise or lower the lens and to tilt it forwards or backwards to control perspective.
Focussing of these plate cameras was by the use of a ground glass screen at the point of focus. Because lens design only allowed rather small aperture lenses, the image on the ground glass screen was faint and most photographers had a dark cloth to cover their heads to allow focussing and composition to be carried out more easily. When focus and composition were satisfactory, the ground glass screen was removed and a sensitised plate put in its place protected by a dark slide. To make the exposure, the dark slide was carefully slid out and the shutter opened and then closed and the dark slide replaced.
Glass plates were later replaced by sheet film in a dark slide for sheet film; adaptor sleeves were made to allow sheet film to be used in plate holders. In addition to the ground glass, a simple optical viewfinder was often fitted.
Cameras which take single exposures on sheet film and are functionally identical to plate cameras are still used for static, high-image-quality work; see Large-format camera, below.
Main article: http://en.wikipedia.org/wiki/View_camera
The large-format camera, taking sheet film, is a direct successor of the early plate cameras and remain in use for high quality photography and for technical, architectural and industrial photography. There are three common types, the view camera with its monorail and field camera variants, and the press camera. They have an extensible bellows with the lens and shutter mounted on a lens plate at the front. Backs taking rollfilm, and digital backs are available in addition to the standard dark slideback. These cameras have a wide range of movements allowing very close control of focus and perspective. Composition and focussing is done on view cameras by viewing a ground-glass screen which is replaced by the film to make the exposure; they are suitable for static subjects only, and are slow to use.
Main article: http://en.wikipedia.org/wiki/Medium-format
Medium-format cameras have a film size between the large-format cameras and smaller 35mm cameras. Typically these systems use 120 or 220 rollfilm. The most common image sizes are 6×4.5 cm, 6×6 cm and 6×7 cm; the older 6×9 cm is rarely used. The designs of this kind of camera show greater variation than their larger brethren, ranging from monorail systems through the classic Hasselblad model with separate backs, to smaller rangefinder cameras. There are even compact amateur cameras available in this format.
Main article: http://en.wikipedia.org/wiki/Folding_camera
The introduction of films enabled the existing designs for plate cameras to be made much smaller and for the base-plate to be hinged so that it could be folded up compressing the bellows. These designs were very compact and small models were dubbed vest pocket cameras. Folding rollfilm cameras were preceded by folding plate cameras, more compact than other designs.
Main article: http://en.wikipedia.org/wiki/Box_camera
Box cameras were introduced as a budget level camera and had few if any controls. The original box Brownie models had a small reflex viewfinder mounted on the top of the camera and had no aperture or focusing controls and just a simple shutter. Later models such as the Brownie 127 had larger direct view optical viewfinders together with a curved film path to reduce the impact of deficiencies in the lens.
Main article: http://en.wikipedia.org/wiki/Rangefinder_camera
As camera and lens technology developed and wide aperture lenses became more common, rangefinder cameras were introduced to make focussing more precise. Early rangefinders had two separate viewfinder windows, one of which is linked to the focusing mechanisms and moved right or left as the focusing ring is turned. The two separate images are brought together on a ground glass viewing screen. When vertical lines in the object being photographed meet exactly in the combined image, the object is in focus. A normal composition viewfinder is also provided. Later the viewfinder and rangefinder were combined. Many rangefinder cameras had interchangeable lenses, each lens requiring its own range- and viewfinder linkages.
Rangefinder cameras were produced in half- and full-frame 35 mm and rollfim (medium format).
Main article: http://en.wikipedia.org/wiki/Single-lens_reflex_camera
In the single-lens reflex camera the photographer sees the scene through the camera lens. This avoids the problem of parallax which occurs when the viewfinder or viewing lens is separated from the taking lens. Single-lens reflex cameras have been made in several formats including sheet film 5x7" and 4x5", roll film 220/120 taking 8,10, 12 or 16 photographs on a 120 roll and twice that number of a 220 film. These correspond to 6x9, 6x7, 6x6 and 6x4.5 respectively (all dimensions in cm). Notable manufacturers of large format and roll film SLR cameras include Bronica, Graflex, Hasselblad, Mamiya, and Pentax. However the most common format of SLR cameras has been 35 mm and subsequently the migration to digital SLR cameras, using almost identical sized bodies and sometimes using the same lens systems.
Almost all SLR cameras used a front surfaced mirror in the optical path to direct the light from the lens via a viewing screen and pentaprism to the eyepiece. At the time of exposure the mirror flipped up out of the light path before the shutter opened. Some early cameras experimented other methods of providing through the lens viewing including the use of a semi transparent pellicle as in the Canon Pellix and others with a small periscope such as in the Corfield Periflex series.
Main article: http://en.wikipedia.org/wiki/Twin-lens_reflex_camera
Twin-lens reflex cameras used a pair of nearly identical lenses, one to form the image and one as a viewfinder. The lenses were arranged with the viewing lens immediately above the taking lens. The viewing lens projects an image onto a viewing screen which can be seen from above. Some manufacturers such as Mamiya also provided a reflex head to attach to the viewing screen to allow the camera to be held to the eye when in use. The advantage of a TLR was that it could be easily focussed using the viewing screen and that under most circumstances the view seen in the viewing screen was identical to that recorded on film. At close distances however, parallax errors were encountered and some cameras also included an indicator to show what part of the composition would be excluded.
Some TLR had interchangeable lenses but as these had to be paired lenses they were relatively heavy and did not provide the range of focal lengths that the SLR could support. Most TLRs used 120 or 220 film; some used the smaller 127 film.
Main article: http://en.wikipedia.org/wiki/Subminiature_camera
Cameras taking film significantly smaller than 35 mm were made. Subminiature cameras were first produced in the nineteenth century. The expensive 8×11 mm Minox, the only type of camera produced by the company from 1937 to 1976, became very widely known and was often used for espionage (the Minox company later also produced larger cameras). Later inexpensive subminiatures were made for general use, some using rewound 16 mm cine film. Image quality with these small film sizes was limited.
Instant picture camera:
Main article: http://en.wikipedia.org/wiki/Instant_camera
After exposure every photograph is taken through pinch rollers inside of the instant camera. Thereby the developer paste contained in the paper 'sandwich' distributes on the image. After a minute, the cover sheet just needs to be removed and one gets a single original positive image with a fixed format. With some systems it was also possible to create an instant image negative, from which then could be made copies in the photo lab. The ultimate development was the SX-70 system of Polaroid, in which a row of ten shots - engine driven - could be made without having to remove any cover sheets from the picture. There were instant cameras for a variety of formats, as well as cartridges with instant film for normal system cameras.
Main article: http://en.wikipedia.org/wiki/Movie_camera
A ciné camera or movie camera takes a rapid sequence of photographs on strips of film. In contrast to a still camera, which captures a single snapshot at a time, the ciné camera takes a series of images, each called a "frame" through the use of an intermittent mechanism.
The frames are later played back in a ciné projector at a specific speed, called the "frame rate" (number of frames per second). While viewing, a person's eyes and brain merge the separate pictures to create the illusion of motion. The first ciné camera was built around 1888 and by 1890 several types were being manufactured. The standard film size for ciné cameras was quickly established as 35mm film and this remains in use to this day. Other professional standard formats include 70 mm film and 16mm film whilst amateurs film makers used 9.5 mm film, 8mm film or Standard 8 and Super 8 before the move into digital format.
The size and complexity of ciné cameras varies greatly depending on the uses required of the camera. Some professional equipment is very large and too heavy to be hand held whilst some amateur cameras were designed to be very small and light for single-handed operation. In the last quarter of the 20th century digital camcorders supplanted film motion cameras for amateurs. Professional video cameras did the same for professional users around the start of the 20th century.
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