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The historic 1949 Zeiss Ikon VEB ContaxS, manufactured in Dresden, the secondpentaprism SLR for eyelevel viewingafter Italian Rectaflex of 1948.
Singlelens reflex cameraFrom Wikipedia, the free encyclopedia
A singlelens reflex camera (SLR) typically uses a mirrorand prism system (hence "reflex", from the mirror'sreflection) that permits the photographer to view through thelens and see exactly what will be captured, contrary toviewfinder cameras where the image could be significantlydifferent from what will be captured.
Contents
1 History1.1 Throughthelens light metering1.2 Semiautomatic exposure capabilities1.3 Fullprogram autoexposure1.4 Autofocus1.5 Digital SLRs
2 Optical components2.1 Pentaprisms and pentamirrors
3 Shutter mechanisms3.1 Focalplane shutters
3.1.1 Rotary focalplane shutter3.2 Leaf shutters
4 Further developments5 Film formats6 Common features7 Advantages8 Disadvantages
8.1 Reliability8.2 Price and affordability
9 Future of SLRs10 See also11 References12 Further reading13 External links
History
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Medium format SLRby Hasselblad
The 1952 (Pentax)Asahiflex, Japan's firstsinglelens reflexcamera
The Contaflex III asinglelens reflexcamera from WestGermany from 1957,with additional115 mm lens
The 35 mm filmbasedNikon F, 1959, theworld's first singlelensreflex system camera
Canon Pellix, 1965
The Pentax SpotmaticIIa, 1971
Olympus The 35 mmfilmbased OlympusOM2 (1975), whichwas the first SLR tomeasure light forelectronic flash at theshutter curtain.
Casio RF2 35mm filmSLR
Nikon F5 professionalSLR, 1996
Digital SLR NikonD200 and a Nikon filmscanner
Prior to the development of SLR, all cameras with viewfinders had two optical light paths: one paththrough the lens to the film, and another path positioned above (TLR or twinlens reflex) or to the side(rangefinder). Because the viewfinder and the film lens cannot share the same optical path, the viewinglens is aimed to intersect with the film lens at a fixed point somewhere in front of the camera. This is not
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problematic for pictures taken at a middle or longer distance, but parallax causes framing errors in closeup shots. Moreover, focusing the lens of a fast reflex camera when it is opened to wider apertures (suchas in low light or while using lowspeed film) is not easy.
Most SLR cameras permit upright and laterally correct viewing through use of a roof pentaprismsituated in the optical path between the reflex mirror and viewfinder. Light, which comes bothhorizontally and vertically inverted after passing through the lens, is reflected upwards by the reflexmirror, into the pentaprism where it is reflected several times to correct the inversions caused by thelens, and align the image with the viewfinder. When the shutter is released, the mirror moves out of thelight path, and the light shines directly onto the film (or in the case of a DSLR, the CCD or CMOSimaging sensor). The Canon Pellix film camera was an exception to the moving mirror system, whereinthe mirror was a fixed beamsplitting pellicle.
Focus can be adjusted manually by the photographer or automatically by an autofocus system. Theviewfinder can include a matte focusing screen located just above the mirror system to diffuse the light.This permits accurate viewing, composing and focusing, especially useful with interchangeable lenses.
Up until the 1990s, SLR was the most advanced photographic preview system available, but the recentdevelopment and refinement of digital imaging technology with an oncamera live LCD preview screenhas overshadowed SLR's popularity. Nearly all inexpensive compact digital cameras now include anLCD preview screen allowing the photographer to see what the CCD is capturing. However, SLR is stillpopular in highend and professional cameras because they are system cameras with interchangeableparts, allowing customization. They also have far less shutter lag, allowing photographs to be timedmore precisely. Also the pixel resolution, contrast ratio, refresh rate, and color gamut of an LCD previewscreen cannot compete with the clarity and shadow detail of a directviewed optical SLR viewfinder.
Large format SLR cameras were probably first marketed with the introduction of C.R. Smith'sMonocular Duplex (USA, 1884).[1] SLRs for smaller exposure formats were launched in the 1920s byseveral camera makers. The first 35mm SLR available to the mass market, Leica's PLOOT reflexhousing along with a 200mm f4.5 lens paired to a 35mm rangefinder camera body, debuted in 1935. TheSoviet Спорт (“Sport”),[2] also a 24mm by 36mm image size, was prototyped in 1934 and went tomarket in 1937. K. Nüchterlein's Kine Exakta (Germany, 1936) was the first integrated 35mm SLR toenter the market. Additional Exakta models, all with waistlevel finders, were produced up to and duringWorld War II. Another ancestor of the modern SLR camera was the Swissmade Alpa, which wasinnovative, and influenced the later Japanese cameras. The first eyelevel SLR viewfinder was patentedin Hungary on August 23, 1943 by Jenő Dulovits, who then 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 eyelevelviewfinder. The Duflex, which went into serial production in 1948, was also the world's first SLR withan instantreturn (a.k.a. autoreturn) mirror.
The first commercially produced SLR that employed a roof pentaprism was the Italian RectaflexA.1000, shown in full working condition on Milan fair April 1948 and produced from September thesame 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 in1954, the Asahiflex IIB. In 1957, the Asahi Pentax combined the fixed pentaprism and the righthandthumb wind lever. Nikon, Canon and Yashica introduced their first SLRs in 1959 (the F, Canonflex, andPentamatic, respectively).
Throughthelens light metering
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As a small matter of history, the first 35 mm camera (nonSLR) to feature through the lens lightmetering may have been Nikon, with a prototype rangefinder camera, the SPX. According to the websitebelow, the camera used Nikon 'S' type rangefinder lenses.[3]
Throughthelens light metering is also known as "behindthelens metering". In the SLR design scheme,there were various placements made for the metering cells, all of which used CdS (Cadmium sulfide)photocells. The cells were either located in the pentaprism housing, where they metered light transmittedthrough the focusing screen; underneath the reflex mirror glass itself, which was Topcon's design; or infront of the shutter mechanism, which was the design used by Canon with their Canon Pellix.
Pentax was the first manufacturer to show an early prototype 35 mm behindthelens metering SLRcamera, which was named the Pentax Spotmatic. The camera was shown at the 1960 Photokina show.However, the first Throughthelens (TTL) light metering SLR on the market was the 1963 Topcon RESuper, which had the CdS metering cell placed behind the reflex mirror. The mirror had narrow slits cutinto the surface to let the light reach the cell providing average metering. Late in the following year, aproduction model of the Pentax Spotmatic was shown whose CdS light meter cells were on thepentaprism, reading the light off the focusing screen providing average reading, yet keeping theSpotmatic name, but now written in one word. Another clever design appeared in 1965, the Canon Pellixemploying a pellicle mirror that is semitransparent, placing the meter cell on an arm swinging into thelightpass behind the mirror for meter reading.
Mamiya Sekor came out with cameras such as the Mamiya Sekor TL and various other versions.Yashica introduced the TL Super. Both of these cameras used M42 screw thread lenses as did the PentaxSpotmatic. Later on Fujica introduced their ST701, then ST801 and ST901 cameras. The ST701 wasthe first SLR to use a silicon cell photodiode, which was more sensitive than CdS and was immune tothe memory effect that the CdS cell suffered from in bright sunlight. Gradually, other 35 mm SLRcamera manufacturers changed their behindthelens meters from CdS cells to Silicon Diode photocells.
Other manufacturers responded and introduced their own behindthelens metering cameras. Nikon andMiranda, at first, simply upgraded their interchangeable pentaprisms to include behindthelens metering(for Nikon F, and Miranda D, F, Fv and G models) and these manufacturers also bought out othercamera models with builtin behindthelens metering capability, such as the Nikkormat FT and theMiranda Sensorex (which used an external coupling diaphragm). Minolta introduced the SRT101,which used Minolta's proprietary system they referred to as "CLC", which was an acronym for "contrastlight compensation", which metered differently from an average metering behindthelens camera.
Some German manufacturers also introduced cameras such as the Zeiss Ikon Contarex family, whichwas one of very few 35 mm SLR to use interchangeable film backs.
Inexpensive leafshutter cameras also benefited from behindthelens metering as, Topcon introducedthe Auto 100 with frontmount interchangeable lenses designed only for that camera, and one of theZeiss Ikon Contaflex leaf shutter cameras. Kowa manufactured their SETR, which had similarspecifications.
Within months, manufacturers decided to bring out models that provided limited area metering, such asNikon's Photomic Tn finder, which concentrated 60% of the CdS cells sensitivity on the inner circle ofthe focusing screen and 30% on the surrounding area. Canon used spot metering in the unusual CanonPellix camera, which also had a stationary mirror system that allowed approximately 70% of the light totravel to the film plane and 30% to the photographer's eye. This system, unfortunately, degraded thenative resolution of the attached lens and provided less illumination to the eyepiece. It did have theadvantage of having less vibration than other SLR cameras but this was not sufficient to attractprofessionals to the camera in numbers.
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Minolta XD11 (also XD7 and XD)
Type 35 mm SLR
Lens Minolta MD mount
Semiautomatic exposure capabilities
While autoexposure was commonly used in the early 1960s with various 35 mm fixed lens rangefindercameras such as the Konica Auto 'S', and other cameras such as the Polaroid Land cameras whose earlymodels used selenium cell meters, autoexposure for interchangeable lens SLRs was a feature that waslargely absent, except for a few early leafshutter SLRs such as the Kowa SER and Topcon Auto 100.
The types of automation found in some of these cameras consisted of the simple programmed shutter,whereby the camera's metering system would select a mechanically set series of apertures with shutterspeeds, one setting of which would be sufficient for the correct exposure. In the case of the abovementioned Kowa and Topcon, automation was semiautomatic, where the camera's CDs meter wouldselect the correct aperture only.
Autoexposure, technically known as semiautomatic exposure, where the camera's metering systemchooses either the shutter speed or the aperture, was finally introduced by the Savoyflex and popularizedby Konishiroku in the 1965 Konica AutoReflex. This camera was of the 'shutterpriority' typeautomation, which meant that the camera selected the correct aperture automatically. This model alsohad the interesting ability to photograph in 35 mm fullframes or halfframes, all selected by a lever.
Other SLRs soon followed, but because of limitations with their lens mounts, the manufacturers of thesecameras had to choose 'aperturepriority' automation, where the camera's metering system selects thecorrect shutter speed. As one example, Pentax introduced the Electro Spotmatic, which was able to usethe then considerable bulk of 42 mm screwmount lenses produced by various manufacturers. Yashica,another screwmount camera manufacturer, soon followed.
Canon, which produced the FD lens mount (known as the breechmount; a unique lens mounting systemthat combines the advantages of screwmount and bayonetmount) introduced their shutter priority35 mm SLR, the Canon EF in 1976 or so. This camera's build quality was almost the equal of theirflagship camera, the Canon F1, and featured a copalsquare vertically travelling focal plane shutter thatcould synchronize electronic flash at shutter speeds up to and including 1/125 of a second, thus makingthis a good secondbody camera for the professional photographer.
Nikon at first produced an aperturepriority camera, but later made subtle changes on the inside of theirbayonet mount, which allowed for shutterpriority automation without obsoleting the photographerslenses.
Fullprogram autoexposure
Fullprogram autoexposure soon followed with theadvent of the Canon A1 in 1978. This SLR had a 'P'mode on the shutter speed dial, and a lock on theaperture ring to allow the lens to be put on 'Auto'mode. Other manufacturers soon followed with Nikonintroducing the FA, Minolta introducing the X700 in1981,[4] and Pentax introducing the Super Program.Olympus, however, continued with 'aperturepriority'automation in their OM system line.
The 1970s and 1980s saw steadily increasing use ofelectronics, automation, and miniaturization,including integrated motor driven film advance withthe Konica FS1 in 1979, and motor rewind functions.
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mount
Focus Manual focus SLR
Exposure Shutter and aperture priorityautoexposure
Flash Hot shoe only; no PC connector
Dimensions 51 × 86 × 136 mm, 560 g
Typical film SLR viewfinderinformation
Autofocus
The first autofocus 35 mm SLR was the Pentax MEFreleased in 1981.[5]
The Minolta Maxxum 7000, released in 1985, was thefirst 35 mm SLR with integrated autofocus andmotorized filmadvance winder, which became thestandard configuration for SLR cameras from then on.This development had significant impact on the photographic industry.
Some manufacturers discarded their existing lens systems to compete with other manufacturer'sautofocus capability in their new cameras. This was the case for Canon, with its new EOS lens line.Other manufacturers chose to adapt their existing lens systems for autofocus capability, as was the casewith Nikon and Pentax. This allowed photographers to continue using their existing lenses, whichgreatly reduced the cost of upgrading. For example, almost all Nikon lenses from the 1960s and laterstill function on the current Nikon bodies, only lacking autofocus. Still some manufacturers, notablyLeica with its Rsystem lenses, and Contax with its Zeiss lenses, decided to keep their lens mounts nonautofocus.
From the late 1980s competition and technical innovations made35 mm camera systems more versatile and sophisticated byadding more advanced light metering capabilities such as spotmetering; limited area metering such as used by Canon with theF1 series; matrix metering as used by Nikon, exposurecommunication with dedicated electronic flash units. The userinterface also changed on many cameras, replacing meter needledisplays that were galvanometerbased and thereby fragile, withlightemitting diodes (LEDs) and then with more comprehensiveliquid crystal displays (LCDs) both in the SLR viewfinder andexternally on the cameras' top plate using an LCD screen.Wheels and buttons replaced the shutter dial on the camera andthe aperture ring on the lens on many models, although somephotographers still prefer shutter dials and aperture rings. Some manufacturers introduced imagestabilization on certain lenses to combat camera shake and to allow longer handheld exposures withoutusing a tripod. This feature is especially useful with long telephoto lenses.
Digital SLRs
Canon, Nikon and Pentax have all developed digital SLR cameras (DSLRs) using the same lens mountsas on their respective film SLR cameras. Konica Minolta did the same, but in 2006 sold their cameratechnology to Sony, who now builds DSLRs based on the Minolta lens mount. Samsung builds DSLRsbased on the Pentax lens mount. Olympus, on the other hand, chose to create a new digitalonly FourThirds System SLR standard, adopted later by Panasonic and Leica.
Contax came out with a DSLR model, the Contax NDigital. This model was too late and too expensiveto be competitive with other camera manufacturers. The Contax Ndigital was the last Contax to use thatmaker's lens system, and the camera, while having impressive features such as a fullframe sensor, wasexpensive and lacked sufficient writespeed to the memory card for it to be seriously considered by someprofessional photographers.
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Focusing screen on Praktica Super TL1000
Crosssection view of SLR system: 1:Frontmount lens (fourelement Tessardesign) 2: Reflex mirror at 45degree angle3: Focal plane shutter 4: Film or sensor 5:Focusing screen 6: Condenser lens 7:Optical glass pentaprism (or pentamirror)8: Eyepiece (can have diopter correctionability)
The digital singlelens reflex camera have largely replaced film SLR's design in convenience, sales andpopularity at the start of 21st century.
Optical components
A crosssection (or 'sideview') of the optical components ofa typical SLR camera shows how the light passes throughthe lens assembly (1), is reflected by the mirror (2) placed ata 45degree angle, and is projected on the matte focusingscreen (5). Via a condensing lens (6) and internal reflectionsin the roof pentaprism (7) the image appears in the eyepiece(8). When an image is taken, the mirror moves upwardsfrom its resting position in the direction of the arrow, thefocal plane shutter (3) opens, and the image is projected ontothe film or sensor (4) in exactly the same manner as on thefocusing screen.
This feature distinguishes SLRs from other cameras as thephotographer sees the image composed exactly as it will becaptured on the film or sensor (see Advantages below).
Pentaprisms and pentamirrors
Most 35 mm SLRs use a roof pentaprism or pentamirror todirect the light to the eyepiece, first used on the 1948Duflex[6] constructed by Jenő Dulovits and patented August1943 (Hungary). With this camera also appeared the firstInstantreturn mirror. The first Japanese pentaprism SLRwas the 1955 Miranda T, followed by the Asahi Pentax,Minolta SR2, Zunow, Nikon F and the Yashica Pentamatic.Some SLRs offered removable pentaprisms with optionalviewfinder capabilities, such as the waistlevel finder, theinterchangeable sports finders used on the Canon F1 andF1n; the Nikon F, F2, F3, F4 and F5; and the Pentax LX.
Another prism design was the porro prism system used inthe Olympus Pen F, the Pen FT, the Pen FV halfframe35 mm SLR cameras. This was later used on the OlympusEVOLT E3x0 series, the Leica Digilux 3 and the Panasonic DMCL1.
A rightangle finder is available that slips onto the eyepiece of most SLRs and DSLRs and allowsviewing through a waistlevel viewfinder. There is also a finder that provides EVF remote capability.
Shutter mechanisms
Focalplane shutters
Almost all contemporary SLRs use a focalplane shutter located in front of the film plane, whichprevents the light from reaching the film even if the lens is removed, except when the shutter is actuallyreleased during the exposure. There are various designs for focal plane shutters. Early focalplane
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A perspective drawing showing how a roofpentaprism corrects a laterally reversedSLR image.
shutters designed from the 1930s onwards usually consistedof two curtains that travelled horizontally across the filmgate: an opening shutter curtain followed by a closingshutter curtain. During fast shutter speeds, the focalplaneshutter would form a 'slit' whereby the second shutter curtainwas closely following the first opening shutter curtain toproduce a narrow, vertical opening, with the shutter slitmoving horizontally. The slit would get narrower as shutterspeeds were increased. Initially these shutters were madefrom a cloth material (which was in later years oftenrubberised), but some manufacturers used other materialsinstead. Nippon Kōgaku (now Nikon Corporation), forexample, used titanium foil shutters for several of theirflagship SLR cameras, including the Nikon F, F2, and F3.
Other focalplane shutter designs, such as the Copal Square,travelled vertically — the shorter travelling distance of 24 millimetres (as opposed to 36 mmhorizontally) meant that minimum exposure and flash synchronisation times could be reduced. Theseshutters are usually manufactured from metal, and use the same movingslit principle as horizontallytravelling shutters. They differ, though, in usually being formed of several slats or blades, rather thansingle curtains as with horizontal designs, as there is rarely enough room above and below the frame fora onepiece shutter. Vertical shutters became very common in the 1980s (though Konica, Mamiya, andCopal first pioneered their use in the 1950s and 1960s, and are almost exclusively used for new cameras.Nikon used Copalmade vertical plane shutters in their Nikomat/Nikkormat range, enabling xsyncspeeds from 1∕30 to 1∕125 while the only choice for focal plane shutters at that time was 1∕60. Later, Nikonagain pioneered the use of titanium for vertical shutters, using a special honeycomb pattern on the bladesto reduce their weight and achieve worldrecord speeds in 1982 of 1∕4000 second for nonsync shooting,
and 1∕250 with xsync. Nowadays most such shutters are manufactured from cheaper aluminium (thoughsome highend cameras use materials such as carbonfibre and Kevlar).
Rotary focalplane shutter
One unusual design, the Olympus Pen halfframe 35 mm SLR system, manufactured by Olympus inJapan, used a rotary focalplane shutter mechanism that was extremely simple and elegant in design.This shutter used titanium foil but consisted of one piece of metal with a fixed opening, which allowedelectronic flash synchronisation up to and including its maximum speed of 1/500 of a second – rivallingthe capabilities of leafshutter systems
Another 35 mm camera system that used a rotary shutter, was the Robot Royal cameras, most of whichwere rangefinder 35 mm cameras. Some of these cameras were fullframe; some were halfframe, and atleast one Robot camera produced an unusual squaresized image on the 35 mm frame.
The Mercury II, produced in 1946, also used a rotary shutter. This was a halfframe 35mm camera.
Leaf shutters
Another shutter system is the leaf shutter, whereby the shutter is constructed of diaphragmlike bladesand can be situated either between the lens or behind the lens. If the shutter is part of a lens assemblysome other mechanism is required to ensure that no light reaches the film between exposures.
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Parts
An example of a behindthelens leaf shutter is found in the 35 mm SLRs produced by Kodak, with theirRetina Reflex camera line; Topcon, with their Auto 100; and Kowa with their SER and SETR reflexes.
A primary example of a mediumformat SLR with a betweenthelens leaf shutter system would beHasselblad, with their 500C, 500CM, 500 ELM (a motorized Hasselblad) and other models (producinga 6 cm square negative). Hasselblads use an auxiliary shutter blind situated behind the lens mount andthe mirror system to prevent the fogging of film.
Other mediumformat SLRs also using leaf shutters include the now discontinued ZenzaBronica camerasystem lines such as the Bronica ETRs, the ETRs'i (both producing a 6 × 4.5 cm. image), the SQ and theSQAI (producing a 6 × 6 cm image like the Hasselblad), and the ZenzaBronica G system (6 × 7 cm).Certain Mamiya mediumformat SLRs, discontinued camera systems such as the Kowa 6 and a fewother camera models also used betweenthelens leaf shutters in their lens systems.
Thus, any time a photographer purchased one of these lenses, that lens included a leaf shutter in its lensmount.
Because leaf shutters synchronized electronic flash at all shutter speeds especially at fast shutter speedsof 1∕500 of a second or faster, cameras using leaf shutters were more desirable to studio photographerswho used sophisticated studio electronic flash systems.
Some manufacturers of mediumformat 120 film SLR cameras also made leafshutter lenses for theirfocalplaneshutter models. Rollei made at least two such lenses for their Rolleiflex SL66 mediumformat which was a focalplane shutter SLR. Rollei later switched to a camera system of leafshutterdesign (e.g., the 6006 and 6008 reflexes) and their current mediumformat SLRs are now all of thebetweenthelens shutter design.
Further developments
Since the technology became widespread in the1970s, SLRs have become the main photographicinstrument used by dedicated amateur photographersand professionals. Some photographers of staticsubjects (such as architecture, landscape, and somecommercial subjects), however, prefer view camerasbecause of the capability to control perspective.[7]With a tripleextension bellows 4" × 5" camera suchas the Linhof SuperTechnika V, the photographercan correct certain distortions such as "keystoning",where the image 'lines' converge (i.e., photographinga building by pointing a typical camera upward toinclude the top of the building). Perspectivecorrection lenses are available in the 35 mm andmedium formats to correct this distortion with filmcameras, and it can also be corrected after the factwith photo software when using digital cameras. The photographer can also extend the bellows to its fulllength, tilt the front standard and perform photomacrography (commonly known as 'macrophotography'), producing a sharp image with depthoffield without stopping down the lens diaphram.
Film formats
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Cutaway of a Minolta XE filmbasedSLR
Early SLRs were built for large format photography, but this film format has largely lost favor amongprofessional photographers. SLR filmbased cameras have been produced for most film formats as wellas for digital formats. These filmbased SLRs use the 35 mm format as, this film format offers a varietyof emulsions and film sensitivity speeds, usable image quality and a good market cost. 35 mm filmcomes in a variety of exposure lengths: 20 exposure, 24 exposure and 36 exposure rolls. Medium formatSLRs provide a higherquality image with a negative that can be more easily retouched than the smaller35 mm negative, when this capability is required.
A small number of SLRs were built for APS such as the Canon IX series and the Nikon Pronea cameras.SLRs were also introduced for film formats as small as Kodak's 110, such as the Pentax Auto 110, whichhad interchangeable lenses.
Common features
Other features found on many SLR cameras include throughthelens (TTL) metering and sophisticated flash control referred to as"dedicated electronic flash". In a dedicated system, once thededicated electronic flash is inserted into the camera's hot shoeand turned on, there is then communication between camera andflash. The camera's synchronization speed is set, along with theaperture. Many camera models measure the light that reflects offof the film plane, which controls the flash duration of theelectronic flash. This is denoted TTL flash metering.
Some electronic flash units can send out several short bursts oflight to aid the autofocus system or for wireless communicationwith offcamera flash units. A preflash is often used todetermine the amount of light that is reflected from the subject,which sets the duration of the main flash at time of exposure.Some cameras also employ automatic fillflash, where the flashlight and the available light are balanced. While these capabilitiesare not unique to the SLR, manufacturers included them early onin the top models, whereas the best rangefinder cameras adoptedsuch features later.
Advantages
Many of the advantages of SLR cameras derive from viewingand focusing the image through the attached lens. Most othertypes of cameras do not have this function; subjects are seenthrough a viewfinder that is near the lens, making the photographer's view different from that of the lens.SLR cameras provide photographers with precision; they provide a viewing image that will be exposedonto the negative exactly as it is seen through the lens. There is no parallax error, and exact focus can beconfirmed by eye—especially in macro photography and when photographing using long focus lenses.The depth of field may be seen by stopping down to the attached lens aperture, which is possible onmost SLR cameras except for the least expensive models. Because of the SLR's versatility, mostmanufacturers have a vast range of lenses and accessories available for them.
Compared to most fixedlens compact cameras, the most commonly used and inexpensive SLR lensesoffer a wider aperture range and larger maximum aperture (typically f/1.4 to f/1.8 for a 50 mm lens).This allows photographs to be taken in lower light conditions without flash, and allows a narrower depth
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During an exposure, the viewfinder isblocked
of field, which is useful for blurring the background behind the subject, making the subject moreprominent. "Fast" lenses are commonly used in theater photography, portrait photography, surveillancephotography, and all other photography requiring a large maximum aperture.
The variety of lenses also allows for the camera to be used and adapted in many different situations. Thisprovides the photographer with considerably more control (i.e., how the image is viewed and framed)than would be the case with a view camera. In addition, some SLR lenses are manufactured withextremely long focal lengths, allowing a photographer to be a considerable distance away from thesubject and yet still expose a sharp, focused image. This is particularly useful if the subject includesdangerous animals (e.g., wildlife); the subject prefers anonymity to being photographed; or else, thephotographer's presence is unwanted (e.g., celebrity photography or surveillance photography).Practically all SLR and DSLR camera bodies can also be attached to telescopes and microscopes via anadapter tube to further enhance their imaging capabilities.
Disadvantages
In most cases, singlelens reflex cameras cannot be made as small or as light as other camera designs—such as rangefinder cameras, autofocus compact cameras and digital cameras with electronicviewfinders (EVF)—owing to the mirror box and pentaprism/pentamirror. The mirror box also preventslenses with deeply recessed rear elements from being mounted close to the film or sensor unless thecamera has a mirror lockup feature; this means that simple designs for wide angle lenses cannot be used.Instead, larger and more complex retrofocus designs are required.
The SLR mirror 'blacksout' the viewfinder image during theexposure. In addition, the movement of the reflex mirror takestime, limiting the maximum shooting speed. The mirror systemcan also cause noise and vibration. Partially reflective (pellicle)fixed mirrors avoid these problems and have been used in a veryfew designs including the Canon Pellix and the Canon EOS1NRS, but these designs introduce their own problems. Thesepellicle mirrors reduce the amount of light travelling to the filmplane or sensor and also can distort the light passing throughthem, resulting in a lesssharp image. To avoid the noise andvibration, many professional cameras offer a mirror lockupfeature, however, this feature totally disables the SLR's automaticfocusing ability. Electronic viewfinders have the potential to give the 'viewingexperience' of a DSLR(throughthelens viewing) without many of the disadvantages. More recently, Sony have resurrected thepellicle mirror concept in their "singlelens translucent" (SLT) range of cameras.
Reliability
SLRs vary widely in their construction and typically have bodies made of plastic or magnesium. Mostmanufacturers do not cite durability specifications, but some report shutter life expectancies forprofessional models. For instance, the Canon EOS 1Ds MkII is rated for 200,000 shutter cycles and thenewer Nikon D3 is rated for 300,000 with its exotic carbon fiber/kevlar shutter. Because many SLRshave interchangeable lenses, there is a tendency for dust, sand and dirt to get into the main body of thecamera through the mirror box when the lens is removed, thus dirtying or even jamming the mirrormovement mechanism or the shutter curtain mechanism itself. In addition, these particles can also jam orotherwise hinder the focusing feature of a lens if they enter into the focusing helicoid. The problem ofsensor cleaning has been somewhat reduced in DSLRs as some cameras have a builtin sensor cleaningunit.
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Price and affordability
The price of SLRs in general also tends to be somewhat higher than that of other types of cameras,owing to their internal complexity. This is compounded by the expense of additional components, suchas flashes or lenses. The initial investment in equipment can be prohibitive enough to keep some casualphotographers away from SLRs, although the market for used SLRs has become larger particularly asphotographers migrate to digital systems.
Future of SLRs
The digital singlelens reflex camera have largely replaced film SLR's design in convenience, sales andpopularity at the start of 21st century. These cameras are currently the marketing 'favorite' amongadvanced amateur and professional photographers. Film based SLR's are still used by a niche market ofenthusiasts and format lovers.[8]
See also
Asahi PentaxFujifilmLenses for SLR and DSLR camerasScheimpflug principleZeiss Ikon
References
1. ^ One was patented in 1861 (Thomas Sutton), but it is not clear if a second example was ever produced;Calvin Rae Smith's design of a Patent Monocular Duplex camera was advertised and sold. Spira, The Historyof Photography, 119.
2. ^ A. O. Gelgar's Sport3. ^ Stephen, Gandy. "Nikon Shibata Book" (http://www.cameraquest.com/nrfstory.htm). Stephen Gandy'sCameraQuest. Retrieved 20080608.
4. ^ "The Rokkor Files the minolta x700" (http://www.rokkorfiles.com/X700.html). The Rokkor Files.November 23, 2010. Retrieved 20101123.
5. ^ Pentax Imaging Company. "History of Innovations 1980–1989"(http://www.pentaximaging.com/world_of_pentax/history_of_innovations/19801989/index.jsp). Pentaxhistory of innovations. Retrieved 20061022.
6. ^ "Article at Photopedia" (http://bichkov.com/photopedia/index.php?title=SLR_Camera). Bichkov.com. 20080123. Retrieved 20131015.
7. ^ Tal, Guy. "Introduction to Large Format" (http://www.naturephotographers.net/articles0703/gt07031.html).Nature Photographers Online Magazine. Retrieved 20070828.
8. ^ ARRI, Panavision, and Aaton Cease Production of Film Cameras; Will Focus Exclusively on Digital(http://collider.com/filmcameraproductionendedarripanavisionaaton/)
Further reading
2/10/2015 Singlelens reflex camera Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Singlelens_reflex_camera 13/13
Wikimedia Commons hasmedia related to SLRcameras.
Spira, S. F. The History of Photography as Seen through the Spira Collection. New York:Aperture, 2001. ISBN 0893819530.Antonetto, Marco: "Rectaflex The Magic Reflex". Nassa Watch Gallery, 2002. ISBN 8887161011
External links
Photography in Malaysia's Contax History, Part II
(http://www.mir.com.my/rb/photography/htmls/contax_history/history2.htm).'Innovative Cameras' by Massimo Bertacchi (http://www.webcitation.org/query?url=http://www.geocities.com/RainForest/Andes/3256/innocams.html&date=20091025+09:41:30)
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Categories: Cameras by type SLR cameras
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