A pellicle mirror is an ultra-thin, ultra-lightweight semi-transparent mirror employed in the light path of an optical instrument, splitting the light beam into two separate beams, both of reduced light intensity. Splitting the beam allows its use for multiple purposes simultaneously; the thinness of the mirror eliminates beam or image doubling due to a non-coincident weak second reflection from the nominally non-reflecting surface, a problem with mirror-type beam splitters. In photography, the pellicle mirror has been employed in single-lens reflex cameras, at first to enable through-the-lens exposure measurement and to reduce camera shake, but most to enable fast series photography, which otherwise would be slowed down by the movement of the reflex mirror, while maintaining constant finder vision; the first use of pellicle mirrors for consumer photography however where in color separation cameras. The Devin Tricolor Camera from at least the 1938 version used two pellicle mirrors plus three color filters to split the image from a single lens into three images of the three additive primary colors.
Pellicle mirrors are ideal for this purpose today, since they are lighter and cheaper than an optical block of dichroic prisms, which would be heavy and expensive for large, high resolution film or plates. The conventional SLR camera has a reflex mirror directing the light beam from the lens to the focusing screen in the viewfinder, swung out of the light path when the exposure is made and causing the viewfinder to go dark; this action adds a delay between pressing the actual exposure of the film. The first camera to employ the pellicle mirror as a beam splitter for the viewfinder was the Canon Pellix, launched by Canon Camera Company Inc. Japan in 1965; the object was to accomplish exposure measurement through the lens, pioneered by Tokyo Kogaku KK, Japan in the 1963 Topcon RE Super. That employed a CdS meter cell placed behind the reflex mirror that had narrow slits cut into the surface to let the light reach the cell. Canon fixed; the meter cell was swung into the light-path behind the mirror by operating a lever on the right-hand camera front for stopped down exposure reading, momentarily dimming the viewfinder.
Two thirds of the light from the camera lens was let through the mirror, while the rest was reflected up to the viewfinder screen. The Pellix pellicle mirror was an ultra-thin Mylar film with a vapour deposited semi reflecting layer. Since there was no mirror blackout, the user could see the image at the moment of exposure; the next 35mm SLR camera to employ the pellicle mirror was the Canon F-1 High Speed, made available in the event of the 1972 Olympic games, the object being rapid series photography, difficult at the time to obtain with a moving mirror. The mirror design was the same as in the Pellix. In 1984, Canon released another version of their "New F-1", which attained a record 14 frames per second performance, being the fastest analog SLR of that time. Nippon Kogaku KK, Japan introduced their high-speed Nikon F2H in 1976; the mirror is a pellicle rather than a conventional front surfaced mirror that swings out of the light path when the exposure is made. To identify the F2H, note the shutter speed dial has no T, B or 1/2000.
Two further Canon models were produced with pellicle mirrors, the EOS RT and the EOS-1N RS, the RT being based on the EOS 600/EOS 630 and the 1N RS being based on the EOS-1N. As development of SLR cameras has progressed since these early models, fast sequence shooting has become possible using ordinary moving mirrors in high-speed cameras, getting rid of the vulnerable pellicle mirror, prone to dust and dirt; the mirror mechanism of conventional SLR cameras has improved since the Pellix mirror was introduced. Digital SLR cameras are able to take ten frames or more per second employing an instant-return mirror. Sony has introduced cameras with plastic pellicle-like mirrors, which it describes as "Single-Lens Translucent" cameras; these cameras divert a portion of incoming light to a phase-detection autofocus unit, while the remaining light strikes a digital image sensor. Sony "SLT" cameras employ an electronic viewfinder allowing exposure value, white balance and other settings to be verified and adjusted visually before taking a picture, although the EVF displays far less dynamic range than the sensor.
The refresh rate of the viewfinder is limited by the time it takes the sensor to make a usable exposure. "SLT" cameras lack a real-time view at high shooting rates, when the viewfinder shows the last picture taken instead of the one being taken — a phenomenon comparable to certain older SLRs that can only achieve their maximum burst rate in mirror lock-up. Few film movie cameras have been made; the earliest is the Pathé WEBO M, m for membrane, of 1946. With that camera light is reflexed sideways into a primary plano-convex finder lens, the plane side being or matted. Another French amateur movie camera with a pellicle is the Christen Reflex for Double-Eight film, it was made from 1960 on and provides a slanted deflection. In 1967, the professional Mitchell NCR and BNCR cameras were equipped with a pellicle-based finder. In the Soviet Union in 1970 appeared the Kiev 16 Alpha featuring a pellicle mirror finder system that deflects str
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
Bell & Howell
Bell and Howell is a U. S.-based services organization and former manufacturer of motion picture machinery, founded in 1907 by two projectionists, was headquartered in Wheeling, Illinois. The company is now headquartered in Durham, North Carolina, provides services for automated equipment in enterprise-level companies. According to its charter, the Bell & Howell Company was incorporated on February 17, 1907, it was duly recorded in the Cook County Record Book eight days later. The first meeting of stockholders took place in the office of Attorney W. G. Strong on February 19 at 10 a.m. The first board of directors was chosen for a term of one year: chairman. Bell & Howell Co. was an important supplier of many different media technologies. The firm built its name making such products as: A rotary framer on 35mm film projectors in 1907 A 35mm film perforator in 1908 Professional 35mm motion-picture film cameras from 1909 on Printing equipment used by motion-picture film laboratories since 1911 The Standard Cinematograph Type 2709 hand-cranked camera Newsreel and amateur film cameras such as the Filmo and Eyemo, Autoload EE Military 16mm film gun camera TYPE N-6A Regular-8 and Super-8 film cameras and projectors 16mm silent and sound projectors.
Slide projectors 35 mm filmstrip projectors. Overhead presentation projectors In 1934, Bell & Howell introduced their first amateur 8mm movie projector, in 1935 the Filmo Straight Eight camera, in 1936 the Double-Run Filmo 8; the 1938 Kodak cassette holding 25 feet of Double-Eight film was taken by the Filmo Auto-8 in 1940. In 1954, Bell & Howell purchased DeVry Industries' 16mm division. Although known for manufacturing their film projectors, a partnership with Canon between 1961 and 1976 offered still cameras. Many of their 35mm SLR cameras were manufactured by Canon with the Bell & Howell logo or Bell & Howell/Canon in place of the Canon branding; the firm dropped the production of movie cameras by the end of the 1970s. Bell & Howell was a supplier of media equipment for offices; the film laboratory line is now a separate company, BHP Inc, a division of Research Technology International. The firm added microfilm products in 1946, it purchased University Microfilms International in the 1980s. UMI produced.
In the 2000s, Bell & Howell decided to focus on their information technology businesses. The imaging business was sold to Eastman Kodak and the international mail business was sold to Pitney Bowes. On June 6, 2001, Bell & Howell became a ProQuest Company, a publicly traded company, but is now a subsidiary of the private Cambridge Information Group. In September 2001, the remaining industrial businesses, along with the Bell & Howell name were sold to private equity firm Glencoe Capital; the company merged with the North American arm of Böwe Systec Inc. In 2003, Böwe Systec acquired the entire company, it was known as Böwe Bell & Howell until 2011, when Versa Capital Management bought the company out of bankruptcy and renamed the company "Bell and Howell, LLC". They had an Electronics and Instrumentation Division on Lennox Road, Basingstoke, UK; this facility produced several different types of transducers for applications such as North Sea oil platforms and the Ariane Space vehicles. Bell & Howell marketed a specially designed Apple II Plus computer to the educational market beginning in July 1979.
The modified Apple had additional security elements for classroom use such as a tamper-proof cover. The case color was black but the inside was a standard Apple II Plus; the modified Apple II became known colloquially among computer enthusiasts as the "Darth Vader" Apple II due to its black case design. Bell & Howell founded an Education Group within their company in 1907; this Education Group created Bell & Howell Schools in 1966. In that same year, the Education Group purchased a controlling share of DeVry Institute of Technology. Two years in 1968, Bell & Howell’s Education Group, via a controlling interest in DeVry, acquired Ohio Institute of Technology in Columbus, Ohio. Over the years, the Education Group has bought and sold large interests in a variety of educational organizations and institutions. Charles H. Percy Abraham Zapruder BH Film perforation TeleMation Inc. In 1977, TeleMation inc. became a division of Howell. Pocket comparator Notes BibliographyUnlocking the Vault Dated November 13, 2000, viewed December 7, 2006 BHP Inc Website viewed December 7, 2006 Official website European & International Sector.
The Zapruder Camera Bell & Howell 414PD Director Series - Overview and User's Manual. Bell & Howell at Made in Chicago Museum
The Canon F-1 is a 35 mm single-lens reflex camera produced by Canon of Japan from March 1971 until the end of 1981, at which point it had been superseded by the New F-1 launched earlier that year. The Canon FD lens mount was introduced along with the F-1, but the previous Canon FL-mount lenses and older R- series lenses were compatible with the camera with some limitations; the Canon F-1 was marketed as a competitor to the Nikon F and Nikon F2 single lens reflex cameras by Nikon. The F-1 was Canon's first professional-grade SLR system, supporting a huge variety of accessories and interchangeable parts so it could be adapted for different uses and preferences. In 1972 Canon launched a Highspeed model with a fixed pellicle mirror that allowed the user to see the subject at all times. Equipped with a motor drive, the camera was able to shoot up to 9 frames per second—the highest speed of any motor driven camera at the time; the Canon F-1 uses the Canon FD lens mount, introduced alongside the camera.
Between 1970 and 1979, a total of 68 different FD mount lens models were produced, ranging from 7.5mm to 800mm in focal length. Most earlier FL and R series lenses are compatible with the F-1, though they must be used in stop-down metering mode. One exception is the FLP 38 mm F2.8, designed for the Canon Pellix. This lens' rear element extends further into the camera body than other FL-mount lenses, would obstruct the moving mirror of the Canon F-1. Canon introduced a number of innovations in the FD lens line, including the first use of an aspherical lens element in a 35mm camera system with the release of the FD 55mm f/1.2 AL in. Canon's super telephoto FD lenses were the first to use white-colored housings, which were designed to keep the thermally sensitive fluorite lens elements from expanding or cracking. Canon continues to use white housings for its L-series lenses today, though the modern versions are made with ultra-low dispersion glass rather than fluorite; the Canon F-1 has one of the largest set of accessories of any 35mm SLR produced.
The viewfinder is removable. Like most professional 35 mm cameras of the 1970s, the F-1 had interchangeable viewfinders. To remove the viewfinder, one depressed the two small buttons at the rear sides of the finder, slid the finder toward the back of the camera; the camera shipped with a standard pentaprism finder, called an "eye-level finder" by Canon. Other finders available included a waist-level finder, Speed Finder, Booster T finder, Servo EE finder; the waist-level finder was patterned after the design of waist-level finders common on medium format cameras. It had a pop-up hood to shield the focusing screen from stray light, as well as a magnifier to help with critical focusing; the waist-level finder did not allow the metering information to be seen. The Speed Finder had a rotation feature, unique to Canon; the speed finder had a unique arrangement of prisms which allowed the entire finder image to be viewed from 60 millimeters away. In addition, the speed finder was arranged in such a way that it could be viewed in either the eye-level or waist-level position.
The speed finder was suggested for use when wearing goggles or anything else that could prevent the user from placing the eyepiece right up to their eye. The Speed finder allowed full metering; the Booster T Finder and Servo EE Finder were both variations on the standard eye-level finder. The Booster T Finder contained an ultra-sensitive metering cell which could read as low as EV −3.5. Just like the metering range was shifted towards the dark side, this finder shift the shutter speeds the camera provided towards the long end. Instead of the normal range, the Booster T Finder gave 60 s – 1/60 s; the shutter speed dial on the finder locked on to the camera's normal shutter dial and drove it through a coupling pin for the standard range of 1 s – 1/60 s. The finder had a trigger button, which went through the finder down to the normal trigger button; when the Booster's shutter speed dial was turned further, towards longer times, the camera's dial stopped at the B setting, the finder kept the trigger button pressed for the duration of the exposure.
The mechanics of this connection resulted in the oddity that there was no 2 s setting, but 4, 3 and 1 seconds. The Servo EE Finder added shutter priority automatic exposure to the F-1. A servo mechanism in the finder drove the aperture lever on the lens, stopping it down to the correct value; this finder used the same coupling pin on the shutter speed dial as the Booster T Finder did, to sync the finder's shutter speed setting with the camera. It required the Motor Drive MF and a special power cord; the originally
The Canon A-1 is an advanced level single-lens reflex 35 mm film camera for use with interchangeable lenses. It was manufactured by Canon Camera K. K. in Japan from April 1978 to 1985. It employs a horizontal cloth-curtain focal-plane shutter with a speed range of 30 to 1/1000 second plus bulb and flash synchronization speed of 1/60 second, it has dimensions of 92 millimetres height, 141 millimetres width, 48 millimetres depth and 620 grams weight. Unlike most SLRs of the time, it was available in only one color; the introductory US list price for the body plus Canon FD 50 mm f/1.4 SSC lens was $625, the camera was sold with a 30–40% discount. The A-1 is a significant camera, it was the first SLR to offer an electronically controlled programmed autoexposure mode. Instead of the photographer picking a shutter speed to freeze or blur motion and choosing a lens aperture f-stop to control depth of field, the A-1 has a microprocessor programmed to automatically select a compromise exposure based on light meter input.
All cameras today have at least one program mode. The A-1 accepts any lens with the Canon FD breech lock Canon New FD pseudo-bayonet mount, it can use most earlier FL lenses and some older R series lenses, albeit with reduced functionality. This excludes all of Canon's EF bayonet mount autofocus lenses. During the late 1970s and 1980s, there were 55 Canon FD lenses available for purchase, they ranged from a 7.5mm f/5.6 fisheye to an FD 800mm f/5.6 telephoto, included lenses with maximum apertures to f/1.2 and a line of L-series lenses of exceptional quality. Accessories for the A-1 included the Canon motor drive MA, the Canon Databack A, the Canon Speedlight 155A and Canon Speedlight 199A electronic flashes; the A-1 is a battery-powered microprocessor-controlled manual-focus SLR with manual exposure control or shutter priority, aperture priority or programmed autoexposure. A fifth mode is "stopped down AE", in which the aperture is closed and alterable by the photographer and the camera selects the shutter speed based on the actual light reading.
This differs from aperture priority in which the aperture is not closed until a photograph is taken and the shutter speed is calculated based on the light measured through the open aperture. Stopped down AE existed so that old FL lenses could be used with at least some kind of AE, was useful for photomicroscopy, manual-aperture lenses, etc; the A-1 is the first SLR to have all four of the now standard PASM exposure modes. It has a viewfinder exposure information system using a six-digit, seven-segment per digit, red alphanumeric LED display on the bottom of the viewfinder to indicate the readings of the built-in centerweighted, silicon photocell light meter; the focusing screen has Canon's standard split image rangefinder and microprism collar focusing help. Beginning with the amateur level Canon AE-1 of 1976, there was a complete overhaul of the entire Canon SLR line; the 1970s and 1980s were an era of intense competition among the major SLR brands: Canon, Minolta and Olympus. Between 1975 and 1985, there was a dramatic shift away from heavy all-metal manual mechanical camera bodies to much more compact bodies with integrated circuit electronic automation.
In addition, because of rapid advances in electronics, the brands continually leapfrogged each other with models having new or more automatic features, less expensive components and assembly. The industry was trying to expand out from the saturated high-end professional market and appeal to the large mass of low-end amateur photographers keen to move up from compact automatic leaf shutter rangefinder cameras to the more "glamorous" SLR but were intimidated by the need to learn all the details of operating a traditional SLR; the A-1 is the high technology standard bearer of the landmark Canon amateur level A-series SLRs. The other members of the A-series are the Canon AE-1, AT-1, AV-1, AE-1 Program and AL-1, they all use the same compact aluminum alloy chassis, but with differing feature levels and outer cosmetic acrylonitrile-butadiene-styrene plastic panels. By sharing most major components, an inexpensive horizontal cloth-curtain shutter, costs could be spread out over a larger production volumes.
The A-1 represented Canon's bid to defeat Nikon through the cheapest price. The A-1 caused a sensation when it was released in early 1978. Most photographers were amazed at its advanced features, years ahead of the competition, but in the face of changing technology, not all comments were positive. Professional photographers worried about the long term reliability of its consumer-level mechanical and electronic components under heavy daily use, the slow flash sync and top shutter speeds. Traditionalist photographers complained about an "excess" of automation ruining the art of photography, a criticism, leveled at all of the newly automated cameras released in the 1980s. However, automation turned out to be the right way to entice many new amateur photographers on a budget, paid off well for Canon; the Canon A-1 was a runaway best seller, as it offered new SLR buyers considerable features and value for the price. It was reliable for its day in amateur usage, but as competitors brought out their own programmed SLRs, the A-1 be
The Canon T90, introduced in 1986, was the top of the line in Canon's T series of 35 mm Single-lens reflex cameras. It is the last professional-level manual-focus camera from Canon, the last professional camera to use the Canon FD lens mount. Although it was overtaken by the autofocus revolution and Canon's new, incompatible EOS after only a year in production, the T90 pioneered many concepts seen in high-end Canon cameras up to the present day the user interface, industrial design, the high level of automation. Due to its ruggedness, the T90 was nicknamed "the tank" by Japanese photojournalists. Many have still rated it even 20+ years after its introduction. Previous Canon cameras had been wholly in-house design projects. For the T90, Canon brought in German industrial designer Luigi Colani in a collaboration with Canon's own designers; the final design was composed of Colani's ideas by Kunihisa Ito of ODS Co. Ltd. incorporating Colani's distinctive "bio-form" curvaceous shapes. Canon considered Colani's contribution important enough to present him with the first production T90 body, engraved with his name.
Computer-aided design techniques were introduced to Canon for the T90, as well as the use of computer controlled milling machines to make the molding dies for the shell. Much work went into human factors engineering to create an ergonomic user interface for the camera; the form of previous cameras was dictated by the required locations of mechanical controls on the body, such as the film advance lever, rewind crank, shutter speed dial, shutter release, etc. On the T90, the film transport control is no longer required, while the others are no longer mechanically linked; this gave the designers more freedom to shape the camera to make it easier to control and hold, to place controls in a way that suited the user rather than a mechanical design. The T90 introduced. While the use of a LCD screen on the top of the camera's right hand side was not new for the T90 – it was introduced on the T70 – the T90 refined it to show more camera information. A control wheel is located behind the shutter release and convenient for the right index finger is used to adjust most camera settings in conjunction with other buttons located for the right thumb and on the left-hand side of the camera.
The T90 includes an integral motor driven film advance, focal plane shutter and aperture cocking and rewind functions. Canon broke new ground with the powered features of the camera. Cameras used one powerful electric motor geared to all functions. Instead, the T90 has three coreless micromotors within the body, close to the functions they drive, for maximum mechanical advantage. One is used achieving a rate of 4.5 frames per second. A second prepares the shutter. A third motor powers the rewind function. All of this is driven by four AA batteries in the base of the camera. To control the camera's systems, the T90 uses a dual CPU architecture; the main, low-power CPU runs at 32 kHz while the sub-CPU runs at 1 MHz, is powered down when not needed. The main CPU handles the LCD display and overall state, while the sub-CPU handles exposure calculations, viewfinder display, control of the camera's motors; this architecture provides for lower power usage. Both CPUs, plus other integrated circuits and components, are mounted on several flexible circuit boards that fit around the camera's structure.
A coin-type lithium battery on the main circuit board retains camera settings when the AA batteries are removed. This is not a user-serviceable part, when it fails the camera has to be brought to a service center where the battery can be replaced by a Canon technician. Expected battery life is on the order of five years, although this depends on a variety of factors including the duration of periods without main battery power. For the T90, Canon developed their most sophisticated light-metering system yet. Although it introduced no novel metering techniques, it assembled the majority of the metering techniques developed into one easy-to-use system. First, it took the metering options from the New F-1—center-weighted average metering, partial area metering, spot metering—and makes them available with a press of a button and a turn of the command dial; the New F-1 requires a focusing screen change to switch metering patterns. On the T90, partial area metering uses the center 13% of the picture area, while spot metering uses the center 2.7%.
To these, Canon copied the metering options found on Olympus' OM-4. Multi-spot metering allows the photographer to average up to eight spot meter readings from different parts of the scene. In another feature borrowed from Olympus, separate Highlight and Shadow spot readings could be taken; these adjust the camera's metering decisions to ensure extremes of tonal range are not muted and grey in the final exposure. Two built-in sensors are used to implement all these metering options. Center-weighted and partial area metering are performed by a double-area silicon photocell in Canon's standard location above the eyepiece, while spot metering is performed by another SPC located at the bottom of the mirror box. Light reaches that sensor via a half-silvered area of the main mirror and a secondary mirror located beneath it; the spot metering cell allows for automatic TTL "off-the-film" flash metering, again borrowed from Olympus. Notably lacking is, matrix metering. Nikon had introduced this in the FA in 1983, but Canon did not follow suit until 1987's EOS 650.
Eight exposure modes are available. Program AE mode puts
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