A camera is an optical instrument to capture still images or to record moving images, which are stored in a physical medium such as in a digital system or on photographic film. A camera consists of a lens which focuses light from the scene, a camera body which holds the image capture mechanism; the still image camera is the main instrument in the art of photography and captured images may be reproduced as a part of the process of photography, digital imaging, photographic printing. The similar artistic fields in the moving image camera domain are film and cinematography; the word camera comes from camera obscura, which means "dark chamber" and is the Latin name of the original device for projecting an image of external reality onto a flat surface. The modern photographic camera evolved from the camera obscura; the functioning of the camera is similar to the functioning of the human eye. The first permanent photograph was made in 1825 by Joseph Nicéphore Niépce. A camera works 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 use the same basic design: light enters an enclosed box through a converging/convex lens and an image is recorded on a light-sensitive medium. A shutter mechanism controls the length of time. Most photographic cameras have functions that allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, to control the exposure so that it is not too bright or too dim. On most digital cameras a display a liquid crystal display, permits the user to view the scene to be recorded and settings such as ISO speed and shutter speed. A movie camera or a video camera operates to a still camera, except it records a series of static images in rapid succession at a rate of 24 frames per second; when the images are combined and displayed in order, the illusion of motion is achieved. Traditional cameras capture light onto photographic film.
Video and digital cameras use an electronic image sensor a charge coupled device or a CMOS sensor to capture images which can be transferred or stored in a memory card or other storage inside the camera for playback or processing. Cameras that capture many images in sequence are known as movie cameras or as ciné cameras in Europe; however these categories overlap as still cameras are used to capture moving images in special effects work and many modern cameras can switch between still and motion recording modes. A wide range of film and plate formats have been used by cameras. In the early history plate sizes were specific for the make and model of camera although there 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 and 135 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 was 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, 16 mm film, introduced in the US in 1923, soon became the standards for "home movies" in their respective hemispheres. In 1932, the more economical 8 mm format was created by doubling the number of perforations in 16 mm film splitting it after exposure and processing; the Super 8 format, still 8 mm wide but with smaller perforations to make room for larger film frames, was introduced in 1965. Traditionally used to "tell the camera" the film speed of the selected film on film cameras, film speed numbers are employed on modern digital cameras as an indication of the system's gain from light to numerical output and to control the automatic exposure system.
Film speed is measured via the ISO system. The higher the film speed number the greater the film sensitivity to light, whereas with a lower number, the film is less sensitive to light. On digital cameras, electronic compensation for the color temperature associated with a given set of lighting conditions, ensuring that white light is registered as such on the imaging chip and therefore that the colors in the frame will appear natural. On mechanical, film-based cameras, this function is served by the operator's choice of film stock or with color correction filters. In addition to using white balance to register natural coloration of the image, photographers may employ white balance to aesthetic end, for example, white balancing to a blue object in order to obtain a warm color temperature; the lens of a camera brings it to a focus on the sensor. 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 Leitz. Camera lenses are
A pentaprism is a five-sided reflecting prism used to deviate a beam of light by a constant 90° if the entry beam is not at 90° to the prism. The beam reflects inside the prism twice, allowing the transmission of an image through a right angle without inverting it as an ordinary right-angle prism or mirror would; the reflections inside the prism are not caused by total internal reflection, since the beams are incident at an angle less than the critical angle. Instead, the two faces are coated to provide mirror surfaces; the two opposite transmitting faces are coated with an antireflection coating to reduce spurious reflections. The fifth face of the prism is not used optically but truncates what would otherwise be an awkward angle joining the two mirrored faces. A variant of this prism is the roof pentaprism, used in the viewfinder of single-lens reflex cameras; the camera lens renders an image, both vertically and laterally reversed, the reflex mirror re-inverts it leaving an image laterally reversed.
In this case, the image needs to be reflected left-to-right as the prism transmits the image formed on the camera's focusing screen. This lateral inversion is done by replacing one of the reflective faces of a normal pentaprism with a "roof" section, with two additional surfaces angled towards each other and meeting at 90°, which laterally reverses the image back to normal. Reflex cameras with waist-level finders, including many medium format cameras, display a laterally reversed image directly from the focusing screen, viewed from above. In surveying a double pentaprism and a plumb-bob are used to stake out right angles, e.g. on a construction site. Pentamirror Single-lens reflex camera Digital single-lens reflex camera Retroreflector
Single-lens reflex camera
A single-lens reflex camera is a camera that uses a mirror and prism system that permits the photographer to view through the lens and see what will be captured. With twin lens reflex and rangefinder cameras, the viewed image could be different from the final image; when the shutter button is pressed on most SLRs, the mirror flips out of the light path, allowing light to pass through to the light receptor and the image to be captured. Prior to the development of SLR, all cameras with viewfinders had two optical light paths: one path through the lens to the film, another path positioned above or to the side; because the viewfinder and the film lens cannot share the same optical path, the viewing lens is aimed to intersect with the film lens at a fixed point somewhere in front of the camera. This is not problematic for pictures taken at a middle or longer distance, but parallax causes framing errors in close-up shots. Moreover, focusing the lens of a fast reflex camera when it is opened to wider apertures is not easy.
Most SLR cameras permit upright and laterally correct viewing through use of a roof pentaprism situated in the optical path between the reflex mirror and viewfinder. Light, which comes both horizontally and vertically inverted after passing through the lens, is reflected upwards by the reflex mirror, into the pentaprism where it is reflected several times to correct the inversions caused by the lens, align the image with the viewfinder; when the shutter is released, the mirror moves out of the light path, the light shines directly onto the film. The Canon Pellix, along with several special purpose high speed cameras, were an exception to the moving mirror system, wherein the mirror was a fixed beamsplitting pellicle. Focus can be adjusted manually automatically by an autofocus system; the viewfinder can include a matte focusing screen located just above the mirror system to diffuse the light. This permits accurate viewing and focusing useful with interchangeable lenses. Up until the 1990s, SLR was the most advanced photographic preview system available, but the recent development and refinement of digital imaging technology with an on-camera live LCD preview screen has overshadowed SLR's popularity.
Nearly all inexpensive compact digital cameras now include an LCD preview screen allowing the photographer to see what the CCD is capturing. However, SLR is still popular in high-end and professional cameras because they are system cameras with interchangeable parts, allowing customization, they have far less shutter lag, allowing photographs to be timed more precisely. The pixel resolution, contrast ratio, refresh rate, color gamut of an LCD preview screen cannot compete with the clarity and shadow detail of a direct-viewed optical SLR viewfinder. Large format SLR cameras were first marketed with the introduction of C. R. Smith's Monocular Duplex. SLRs for smaller exposure formats were launched in the 1920s by several camera makers; the first 35mm SLR available to the mass market, Leica's PLOOT reflex housing along with a 200mm f4.5 lens paired to a 35mm rangefinder camera body, debuted in 1935. The Soviet Спорт a 24mm by 36mm image size, was prototyped in 1934 and went to market in 1937. K. Nüchterlein's Kine Exakta was the first integrated 35mm SLR to enter the market.
Additional Exakta models, all with waist-level finders, were produced up to and during World War II. Another ancestor of the modern SLR camera was the Swiss-made Alpa, innovative, influenced the Japanese cameras; the first eye-level SLR viewfinder was patented in Hungary on August 23, 1943 by Jenő Dulovits, who designed the first 35 mm camera with one, the Duflex, which used a system of mirrors to provide a laterally correct, upright image in the eye-level viewfinder. The Duflex, which went into serial production in 1948, was the world's first SLR with an instant-return mirror; the first commercially produced SLR that employed a roof pentaprism was the Italian Rectaflex A.1000, shown in full working condition on Milan fair April 1948 and produced from September the same year, thus being on the market one year before the east German Zeiss Ikon VEB Contax S, announced on May 20, 1949, produced from September. The Japanese adopted and further developed the SLR. In 1952, Asahi developed the Asahiflex and in 1954, the Asahiflex IIB.
In 1957, the Asahi Pentax combined the right-hand thumb wind lever. Nikon and Yashica introduced their first SLRs in 1959; as a small matter of history, the first 35 mm camera to feature through the lens light metering may have been Nikon, with a prototype rangefinder camera, the SPX. According to the website below, the camera used Nikon'S' type rangefinder lenses. Through-the-lens light metering is known as "behind-the-lens metering". In the SLR design scheme, there were various placements made for the metering cells, all of which used CdS photocells; the cells were either located in the pentaprism housing, where they metered light transmitted through the focusing screen. Pentax was the first manufacturer to show an early prototype 35 mm behind-the-lens metering SLR camera, named the Pentax Spotmatic; the camera was shown at the 1960 photokina show. However, the first
In photography, a viewfinder is what the photographer looks through to compose, and, in many cases, to focus the picture. Most viewfinders are separate, suffer parallax, while the single-lens reflex camera lets the viewfinder use the main optical system. Viewfinders are used in many cameras of different types: still and movie, film and digital. A zoom camera zooms its finder in sync with its lens, one exception being rangefinder cameras. Before the development of microelectronics and electronic display devices, only optical viewfinders existed. Direct viewfinders are miniature Galilean telescopes. A declining minority of point and shoot cameras use them. Parallax error results from the viewfinder being offset from the lens axis, to point above and to one side of the lens; the error varies with distance, being negligible for distant scenes, large for close-ups. Viewfinders show lines to indicate the edge of the region which would be included in the photograph; some sophisticated 20th century cameras with direct viewfinders had coincidence rangefinders with separate windows from the viewfinder integrated with it.
Cameras with interchangeable lenses had to indicate the field of view of each lens in the viewfinder. Simple reflecting viewfinders comprised a small forward-looking lens, a small mirror at 45° behind it, a lens at the top; such viewfinders were integrated into box cameras, fitted to the side of folding cameras. These viewfinders were fitted to inexpensive cameras. For many sports and press applications optical viewfinders gave too small an image and were inconvenient to use for scenes that were changing rapidly. For these purposes a simple arrangement of two wire rectangles, a smaller one nearer the eye and a larger one further away, was used, with no optics; this was fast and convenient to use, but not accurate. A sportsfinder is sometimes known as an Albada finder, it is a "viewfinder used with a camera held at eye level. Twin-lens reflex cameras had a large lens above the taking lens, a large mirror at 45°, projecting an image onto a ground glass screen viewable from above, with the camera at waist level.
The viewfinder lens was of similar size and focal length to the taking lens, though the optical quality was less critical. These cameras were expensive. Both single- and twin-lens reflexes allowed focussing by adjusting the lens until the image was sharp. Single-lens reflex cameras viewed the scene through the taking lens. Early SLRs were plate cameras, with a mechanism to insert a mirror between the lens and the film which reflected the light upwards, where it could be seen at waist level on a ground glass screen; when ready to take the picture, the mirror was pivoted out of the way. SLRs had a mechanism which flipped the mirror out of the way when the shutter button was pressed, followed by the shutter opening. Instead of a waist-level arrangement, a prism was used to allow the camera to be held to the eye; the big advantage of the SLR was that other optical device, could be used. The live preview feature of digital cameras share this advantage of the SLR, as they show the image as it will be recorded, with no additional optics or parallax error.
Viewfinders can be optical or electronic. An optical viewfinder is a reversed telescope mounted to see what the camera will see, its drawbacks are many, but it has advantages. An electronic viewfinder is a CRT, LCD or OLED based display device, though only the LCD is commonplace today due to size and weight. In addition to its primary purpose, an electronic viewfinder can be used to replay captured material, as an on-screen display to browse through menus. A still camera's optical viewfinder has one or more small supplementary LED displays surrounding the view of the scene. On a film camera, these displays show shooting information such as the shutter speed and aperture and, for autofocus cameras, provide an indication that the image is focussed. Digital still cameras will also display information such as the current ISO setting and the number of remaining shots which can be taken in a burst. Another display which overlays the view of the scene is provided, it shows the location and state of the camera's provided auto-focus points.
This overlay can provide lines or a grid which assist in picture composition. It is not uncommon for a camera to have two viewfinders. For example, a digital still camera may have an electronic one; the latter can be used to replay captured material, has an on-screen display, can be switched off to save power. A camcorder may have both electronic; the first is viewed through a ma