Single-lens reflex camera

The single-lens reflex (SLR) is a type of camera that uses a movable mirror placed between the lens and the film to project the image seen through the lens to a matte focusing screen. Most SLRs use a roof pentaprism or pentamirror to observe the image via an eyepiece, but there are also other finder arrangements, such as the waist-level finder or porro prism.

The shutter in almost all contemporary SLRs sits just in front of the focal plane (and is called a focal plane shutter). If it does not, some other mechanism is required to ensure that no light reaches the film between exposures. For example, the Hasselblad 500C camera uses an auxiliary shutter blind in addition to its in-lens leaf shutter.

Cross-section view of SLR system:
1) Lens
2) Mirror
3) Shutter
4) Film or sensor
5) Focusing screen
6) Condensing lens
7) Pentaprism
8) Eyepiece

The cross-section (side-view) of the optical components of a typical SLR camera shows how the light passes through the lens assembly (1), is reflected by the mirror (2) and is projected on the matte focusing screen (5). Via a condensing lens (6) and internal reflections in the roof pentaprism (7) the image appears in the eyepiece (8). When an image is taken, the mirror moves in the direction of the arrow, the focal plane shutter (3) opens, and the image is projected onto the film or sensor (4) in exactly the same manner as on the focusing screen.

This feature distinguishes SLRs from other cameras, as the photographer sees the image composed exactly as it will be captured on the film or sensor (see Advantages below).

Since the technology became widespread in the 1970s, SLRs have become the main type of camera used by dedicated amateur photographers and professionals, though some landscape photographers may prefer view cameras.

Olympus OM-2

History

Main article: History of the single-lens reflex camera

Large format SLR cameras were probably first sold in 1884. The Ihagee Kine-Exakta was the first 35 mm SLR and it was truly influential. Further 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, which was innovative, and proved influential for the later Japanese cameras. The first solution for an eye-level viewfinder was patented in Hungary on August 23, 1943, by Jenő Dulovits, who then designed the first 35mm camera that had one implemented: 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 also the world's first SLR with an instant-return (a.k.a. autoreturn) mirror.

The first serially produced SLR that employed a roof pentaprism was the East German Contax S, announced on May 20, 1949.

The Japanese further developed the SLR. In 1952, Asahi developed the Asahiflex and in 1954, the Asahiflex IIB. In 1957, the Asahi Pentax combined the fixed pentaprism and the right-hand thumb wind lever. Nikon, Canon and Yashica introduced their first SLRs in 1959 (the F, Canonflex, and Pentamatic, respectively).

Through-the-lens (TTL) light metering came to the SLR in the early 1960s, with 1962's Topcon RE Super (spot metering) and 1964's Pentax Spotmatic (center-weighted average metering). Auto-exposure was next, introduced by the Savoyflex and popularized by Konishiroku in 1965's Konica Auto-Reflex and its successors. Full-program auto-exposure soon followed. The 1970s and 1980s saw steadily increasing use of electronics, automation, and miniaturization, including integrated motor driven film advance with the Konica FS-1 in 1979, and motor rewind functions.

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  Two Classic 35mm SLR cameras: Canon AE-1 & Minolta X-700
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  Asahiflex
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  The revolutionary Nikon F

Autofocus

The first phase detection SIR TTL autofocus SLR was 1981's Pentax ME-F. The Minolta Maxxum 7000, released in 1985, was the first SLR with integrated motorised autofocus and film advance winder—which became the standard configuration for SLR cameras from then on. This had significant impact on the industry. Some manufacturers discarded their existing systems to enter the AF era, while others chose to adapt their systems for compatibility.

From the late 1980s competition and technical innovations made the camera systems more "intelligent" by adding more advanced light metering, and by allowing the different components to exchange information electronically. The user interface also changed on many cameras, replacing needle display and light-emitting diodes (LEDs) with more comprehensive liquid crystal displays (LCDs) both in viewfinder and externally on the cameras. Wheels and buttons replaced the shutter dial on the camera and the aperture ring on the lens on many models. Some manufacturers also introduced antishake features on some lenses to allow for longer exposure times without a tripod.

Digital SLRs

Main article: Digital single lens reflex cameras

Canon, Nikon, Samsung, Pentax, Minolta, and Sony have developed digital SLR cameras compatible with their film SLR systems (though Konica-Minolta recently sold its SLR camera division to Sony who will continue manufacturing), while Olympus introduced the new digital-only Four Thirds SLR system, adopted later by Panasonic and Leica.

Format

SLR cameras have been produced for most film formats as well as digital formats. Most film SLRs use the 35 mm format, as this offers a good compromise of image quality, size, and cost. Medium format SLRs give a higher quality image when this is required. Digital SLRs (dSLRs) appeared on the market in the late 1990s and as of 2006 are used by many professional photographers as well as amateur enthusiasts. Early SLRs were built for large format photography, but this has largely died out. A small number of SLRs were built for APS but this did not prove popular. SLRs were even built for film formats as small as 110, e.g. the Pentax Auto 110.

Common features

Other features found on many SLR cameras include through-the-lens (TTL) metering and sophisticated flash control. Many models on the market today actually measure the light that bounces off the film, and close the shutter when the picture has had enough exposure.

Likewise, they can send out several short bursts of flash, determine the amount that comes back from the scene, then send out just the right amount of energy for a perfectly exposed photograph. Sophisticated cameras can even make it easy for the photographer to balance flash and available light for the desired look. While these capabilities are hardly unique to the SLR, manufacturers included them early on in the top models, whereas the best rangefinder cameras adopted such features later.

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  Cut-away of a classic Minolta SLR
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Advantages

Many of the advantages of SLR cameras derive from viewing the scene through the taking lens. Most other types of camera do not have this function; subjects are seen through a viewfinder that is near the lens, making the photographer's view different from that of the lens. SLR cameras provide photographers with precision and confidence; they are seeing an image that will be exposed onto the negative exactly as it is seen through the lens. There is no parallax error, and exact focus can be confirmed by eye — otherwise hard for macro photography and when using telephoto lenses. The true depth of field may be seen by stopping down to the taking aperture, possible on all but the cheapest cameras. Because of the SLR's versatility, most manufacturers have a vast range of lenses and accessories available.

Compared to most fixed-lens compact cameras, the most commonly used and cheapest SLR lenses offer 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 of field, which is useful for blurring the background behind the subject, making the subject more prominent. This is commonly used in portrait photography.

The variety of lenses also allows for the camera to be used in very different situations. This gives the photographer considerably more control over how the picture is framed than a simple view camera. In addition, SLR lenses can also be found with extremely long focal lengths, letting a photographer be far away from the subject. This is particularly useful if the subject is dangerous (e.g., wildlife), or the subject would prefer the photographer to stay away (e.g., a celebrity).

Disadvantages

Single-lens reflex cameras cannot be made as small or light as other camera designs — such as rangefinder cameras, autofocus compact cameras and digital cameras with electronic viewfinders (EVF) — owing to the mirror box and pentaprism/pentamirror. The mirror box also prevents lenses from having rear elements closer to the film or sensor; this means that simple designs for wide angle lenses cannot be used. Instead, poorer-performing, larger and more complex retrofocus designs are required.

The SLR mirror blacks out the viewfinder when the picture is taken. In addition, moving the mirror takes time, limiting the maximum shooting speed; the mirror also causes noise and vibration. Partially-reflective (pellicle) fixed mirrors avoid these problems and have been used in a very few designs including the Canon Pellix, but these reduce the light getting to the film or sensor. To avoid the noise and vibration, many professional cameras offer a mirror lock-up feature, but this blacks out the viewfinder totally when in use.

Most digital SLRs in general cannot display a live view on their rear LCD displays, unlike compact or bridge cameras, and must be held to the eye to compose the picture (with the exception of the Olympus E-330, the Panasonic DMC-L1, Leica Digilux 3 and the Canon EOS-1D Mark III). Movie modes are also unavailable. Electronic viewfinders have the potential to give the advantage of a digital SLR (through-the-lens viewing) without many of the disadvantages, but as of 2006 sensor and display technology is insufficient for wide acceptance among the advanced amateur or professional markets that buy digital SLRs.

The price of SLRs in general also tends to be higher than that of other types of cameras, owing to the internal complexity. This is only aggravated by the expense of additional components, such as a flash attachment or various types of lenses. Typically the initial investment in equipment is prohibitive enough to keep the casual photographer away from SLRs.

There is also the obvious problem of a higher rate of breakdowns than a simpler camera of the same build quality. However since SLRs are not aimed at casual users they tend to be built to much higher standard than other camera types making their reliability in practice higher. Because many SLRs have interchangeable lenses, there is a tendency for dust, sand and dirt to get into the main body of the camera, dirtying or even jamming the mirror's movement. In addition, these particles can also jam or otherwise hinder the focusing feature of a lens. This problem has been somewhat reduced in DSLRs as some cameras have a built-in sensor cleaning unit.

Trivia

A camera appears as a charge in the coat of arms of former Lieutenant Governor of Prince Edward Island Gilbert Clements.[1]

SLR chronology

• 1676: reflex mirror first used in a camera obscura.

• 18th century: SLR camera obscuras popular as drawing aids. Artist can trace over the ground glass image to produce a true-life realistic picture.

• 1861: Thomas Sutton (UK) received first patent for SLR photographic camera. An unknown number made but very few; no known production model; no known surviving examples. The manually levered reflex mirror also served as the camera's shutter. Used glass plates.

• 1884: Calvin Rae Smith Monocular Duplex (USA): first known production SLR. Used glass plates (original model 3¼×4¼ inch, later 4×5 inch); many were adapted to use Eastman sheet film. Large-format glass plate or sheet film SLRs were the dominant SLR type until circa 1915. However, SLRs themselves were not commonplace until the 1930s.

• 1900: J.F. Shew & Co Delta Reflex Camera (UK): first focal plane shutter SLR. Used 3¼×4¼ inch plates and had cloth focal plane shutter with speeds to 1/1000th second.

• 1907: Folmer & Schwing Graflex No. 1A (USA): first medium format roll film SLR. Took eight exposures of 2½×4½ inch frames on 116 roll film. Had folding waist level finder and focal plane shutter. Roll film (usually 120 type) SLRs became the dominant SLR type in 1930s.

• 1925: Ernemann (merged into Zeiss Ikon, 1926) Ermanox Reflex (Germany): first SLR with high speed lens (10.5 cm f/1.8 or 85 mm f/1.8 Ernostar). Established SLR as viable photojournalist's available-light camera. Had folding waist level finder and focal plane shutter. Used 4.5×6 cm glass plates or sheet film; adaptable to roll film.

• 1933: Ihagee VP Exakta (Germany): first 127 roll film SLR. First camera with internal flash synchronization. Took eight exposures of 4.5×6 cm frames on 127 roll film. Had folding waist level finder and focal plane shutter. Established standard body shape and handling soon to be standard in 35 mm SLRs except that Exakta SLRs had primarily left-handed controls and were more trapezoidal shaped than rectangular.

• 1935: 135 film, commonly called 35 mm film, introduced by Kodak (USA). Was (and is) 35 mm nominal width (1⅜ inch actual width), acetate base, double perforated film, pre-loaded into felt-lipped, daylight-loading cartridges ready-to-use for still cameras. Originally intended for Kodak Retina, Zeiss Ikon Contax and E. Leitz Leica 35 mm rangefinder cameras. Previously, bulk rolls of 35 mm motion picture film would need to be user cut and loaded, in complete darkness, into camera specific cartridges or magazines. The September 1936 release of Kodachrome (the first high speed (ISO 8 equivalent), realistic color film) in standardized 135 format (but not medium format roll film) spurred explosive growth in the popularity of all types of miniature format 35 mm cameras. The vast majority were not high-end SLRs or RFs, but basic amateur RFs such as the multi-million selling Argus C3 (USA) of 1939. Originally, each US$3.50 (including processing) Kodachrome cartridge gave eighteen exposures if the camera used the 24×36 mm frame size (double the frame size of 35 mm cine cameras) established by the Multi-Speed Shutter Co. Simplex (USA) camera of 1914 and popularized by the E. Leitz Leica A (Germany) of 1925. The 24×36 mm frame size did not become the universal standard frame size until the early 1950s. Note that 135 film cameras using non-standard frame sizes, such as 24×18 mm or 24×24 mm, continued to the made until at least 1990.

• 1935: Possible date of emergence of the Gomz Sport (Спорт), from the Soviet Union; if so, this was the first 35 mm SLR.

• 1936: Ihagee Kine Exakta (Germany): probable first 35 mm SLR. First system SLR, first bayonet lens mount. Had left-handed shutter release and rapid film wind thumb lever, folding waist level finder and 12 to 1/1000th second focal plane shutter. Well integrated design with excellent interchangeable lenses and good accessory system. Fewer than 30,000 Kine Exaktas were made before World War 2 stopped production in 1940. Production of improved models re-started after the war and Exakta was the best known 35 mm SLR brand until 1959.

• 1947: Gamma Duflex (Hungary): first instant return mirror SLR. Had a mirror prism finder, an intermediate step to solid pentaprism. Reflex mirrors coupled to the shutter release had been spring actuated to rise automatically since the 19th century, but the viewfinder would remain blacked-out until the mirror was manually cocked back down. With an automatic, instant return mirror, the viewfinder blackout time might be as short as ⅛th second.

• 1948: Hasselblad 1600F (Sweden): first 2¼ medium format system SLR suitable for professional use. Took twelve exposures of 2¼×2¼ inch (6×6 cm) nominal frames (56×56 mm actual frames) on 120 film. Had modular design accepting interchangeable lenses, film magazines and folding waist level finder. The 1/1600th second corrugated stainless steel focal plane shutter was unreliable and was replaced by a slower but more reliable 1/1000th focal plane shutter in the Hasselblad 1000F (Sweden) of 1952.

• 1948: Alpa Prisma Reflex (Switzerland) had a pentaprism viewfinder in 1948, but its eyepiece was angled upward at 45º.

• 1949: VEB Zeiss Ikon (Dresden) Contax S (East Germany): first pentaprism eyelevel viewing 35 mm SLR. (The Italian Rectaflex Standard came very soon after.) First M42 screw mount camera. (The East German KW Praktica came out at about the same time.) With earlier "waist level" SLR viewfinder systems (in which the photographer looks downward at the reflex mirror's image on the focusing screen), moving subjects are seen to track across the field-of-view in reverse direction of their actual motion, making action shooting counter-intuitive. A pentaprism is a five-sided chunk of glass silvered on two sides that collects, redirects and re-reverses the light from the mirror with minimal light loss. With a proper pentaprism, all a photographer needs to do is hold the camera up to eyelevel and everything is there. The pentaprism SLR had first been proposed in the 19th century and was used in non-35 mm SLRs in the 1930s. Similar systems (or, in the 1990s, its cheaper alternative, the pentamirror) became so common in 35 mm SLRs by the late 1950s that it is the characteristic pentaprism "head" atop the camera body that defines the type for most people.

• 1950: Ihagee Exakta Varex V (East Germany; called V within USA): first interchangeable viewfinder, first interchangeable focusing screens, first viewfinder condenser lens SLR.

• 1950: Angénieux 35mm f/2.5 Retrofocus Type R 1 (France): first retrofocus wide angle lens for 35 mm SLRs. Regular wide angle lenses (meaning short focal length lenses) need to be mounted close to the film. However, SLRs require that lenses be mounted far enough in front of the film to provide space for the movement of the mirror - the "mirror box." Therefore, the focal length of early 35 mm SLR lenses was no less than about 40 mm. This prompted the development of wide lenses with more complex retrofocus optical designs. These use very large negative front elements to force back focus distances long enough to ensure clearance. 35 mm SLR retrofocus wide angle lenses reached field of views as wide as a 13 mm focal length lens (118º) by the early 1980s, but are extremely large compared to non-SLR short focal length lenses because of their gigantic negative elements.

• 1951: Zenit (Soviet Union, Russia; Зенит): first Russian pentaprism eyelevel viewing 35 mm SLR.

• 1951: Asahiflex I (Japan): first Japanese 35 mm SLR. Had folding waist level finder and focal plane shutter.

• 1953: Zeiss Ikon Contaflex I (West Germany): first leaf shutter 35 mm SLR. Had Synchro-Compur leaf shutter and fixed 45 mm f/2.8 Tessar lens. For many years, reliable focal plane shutters were very expensive and SLRs equipped with Compur or Prontor leaf shutters were strong competitors. As focal plane shutters improved, their faster available speeds won out and leaf shutter 35 mm SLRs disappeared around 1973.

• 1954: Asahiflex IIB (Japan; called Sears Tower 22 in USA): first SLR with reliable instant return mirror.

• 1954: Praktina FX (East Germany): first available spring powered motor drive for SLR, first breech-lock lens mount.

• 1956: Kodak Retina Reflex (USA/Germany): first interchangeable lens, leaf shutter 35 mm SLR. Accepted excellent Kodak Retina leaf shutter 35 mm rangefinder interchangeable lenses.

• 1957: Asahi Pentax (Japan; called Sears Tower 26 in USA): first SLR with right-handed rapid-wind thumb lever, first fold-out film rewind crank, first microprism focusing aid. First Asahi SLR with M42 screw mount. Well integrated focal plane shutter, instant return mirror and pentaprism design.

• 1957: Hasselblad 500C (Sweden): replacement of 1600F/1000F's problematic focal plane shutter with reliable interlens Synchro-Compur leaf shutter made the 2¼ medium format SLR the dominant professional studio camera by the late 1950s. Well integrated, durable and reliable design with excellent auto-diaphragm interchangeable lenses and large accessory system.

• 1958: Zunow SLR (Japan): first internal auto-diaphragm (Zunow-matic Diaphragm System) 35 mm SLR and lenses. Well integrated focal plane shutter, instant return mirror, pentaprism and auto-diaphragm design with excellent lenses and good accessory system. Stopping down the lens aperture to prepare for exposure transmits less light to the mirror and the viewfinder may become very dim - perhaps even too dark to see the image. Auto-diaphragms coupled to the shutter release that automatically stop down when the mirror swings up and reopen when the mirror comes down provides almost continuous fully open aperture viewing. Auto-diaphragm lenses and instant return mirror, focal plane shutter SLRs require precise camera-to-lens linkage, but can choreograph the entire shutter-button release, raise mirror, close lens, open shutter, close shutter, open lens, lower mirror exposure sequence in as little as ⅛th second. Originally, these were mechanical spring/gear/lever systems energized concurrent with manually winding the film, but modern systems are electronically timed and electromagnetically powered. The financially weak Zunow company was unable to capitalize on its design; few examples of the camera (and much fewer of the wide and tele lenses for it) were produced before the company switched back to lenses for other companies' cameras.

• 1959: Nikon F (Japan): first pro caliber 35 mm system SLR, first electric motor drive for SLR. (The Japanese Nikon S2 35 mm rangefinder camera had first electric motor drive for any camera type in 1954.) Well integrated, durable and reliable focal plane shutter, instant return mirror, pentaprism and auto-diaphragm design with excellent interchangeable lenses and huge accessory system. Although the F was not technologically ground-breaking, it sold nearly one million units and made the 35 mm SLR the dominant professional miniature format camera (displacing the 35 mm RF) by the early 1960s. The perfection of the optical and mechanical formulae of the interchangeable lens SLR in the one-two punch of the Hasselblad 500C (see above) and Nikon F also ended the popularity of the medium format twin-lens reflex (TLR) camera (typified by the Franke & Heidecke Rolleiflex/Rolleicord series (Germany, later West Germany)) by the early 1960s. The F's improved successor, the Nikon F2 (Japan) of 1971, is widely regarded as the finest mechanically controlled 35 mm SLR camera ever made.

• 1959: Voigtländer–Zoomar 1:2.8 f=36mm–86mm (USA/West Germany): first zoom lens for 35 mm still cameras. Originally mounted for Voigtländer Bessamatic series (West Germany) 35 mm leaf shutter SLRs, but later available in Exakta and other mounts.

• 1960: Royer Savoyflex Automatique (France): first autoexposure SLR. Had unreliable mechanical autoexposure system controlled by external selenium light meter, Prontor leaf shutter and fixed 50 mm f/2.8 Som-Berthiot lens. The first autoexposure still camera was the non-SLR Kodak Super Kodak Six-20 (USA) of 1938 with a mechanical system controlling both aperture and shutter speed via trapped-needle method coupled to external selenium photoelectric cell.

• 1960: Krasnogorsky zavod (KMZ) Narciss (Soviet Union, Russia; Нарцисс): first subminiature SLR. Took 14×21 mm frames on unperforated, specially spooled 16 mm film. Compact design with interchangeable lenses and removable finder. Submini film format cameras (those using smaller than 135 film) have always been unpopular with serious photographers because the very high level of enlargement needed to make even small 3½×5 inch prints from such tiny negatives can magnify normally minor image limitations unless using the highest quality cameras, lenses and films.

• 1962: Nikkorex Zoom 35 (Japan): first 35 mm SLR with fixed zoom lens (Zoom-Nikkor Auto 43–86 mm f/3.5). Had non-pentaprism, four mirror reflex viewfinder and leaf shutter.

• 1963: Olympus Pen F (Japan): first single frame (also called half frame) 35 mm SLR, porroprism SLR. Took up to 72 exposures of vertical 18×24 mm frames on 135 film. Had flat-topped non-pentaprism porroprism reflex and optical relay viewfinder, and rotary focal plane shutter. Well integrated compact design with excellent interchangeable lenses and large accessory system. The original non-SLR Olympus Pen (Japan) of 1960 helped give 35 mm still cameras that used the standard motion picture frame size of 35 mm film a burst of popularity. It ended by the late 1960s. Although single frame cameras used standard 135 film, single frame photofinishing was always special-order. Kyocera/Yashica unsuccessfully attempted to revive the format as "Double 35" with their Yashica Samurai series (Japan) SLRs in 1988.

• 1963: Topcon RE Super (Japan; called Super D in USA): first SLR with through-the-lens (TTL) light meter for convenient exposure control. Had internal CdS cell, match-needle, open aperture metering with auto-diaphragm lenses. Film is rated at a particular "speed" sensitivity. It needs a specific amount of light to form an image. Originally separate selenium photoelectric devices to sense the ambient light, miniature cadmium sulfide (CdS) light meters built into the camera that gave TTL light exposure readings were a great leap forward in convenience that became normal in virtually all 35 mm SLRs by the late 1960s.

• 1964: Asahi (Honeywell in USA) Pentax Spotmatic (Japan): second SLR with TTL metering (stop-down aperture, full area averaging). Well integrated, compact and reliable focal plane shutter, instant return mirror and pentaprism design with excellent non-auto-diaphragm interchangeable lenses. The Spotmatic (and rival TTL metering SLRs, including the Canon FT (1966; stop-down aperture, partial area), Minolta SRT101 (1966; open aperture, modified centerweighted) and Nikkormat FTN (1967; open aperture, centerweighted), all from Japan) made the Japanese 35 mm SLR the dominant advanced amateur camera by the late 1960s.

• 1964: Krasnogorsky zavod (KMZ) Zenit-5 (Soviet Union, Russia; Зенит-5): first SLR with built-in electric motor drive.

• 1965: Canon Pellix (Japan): first pellicle reflex mirror SLR. Virtually all SLRs use fast moving reflex mirrors that swivel out of the way to take the picture, causing mirror shock vibration, blacking-out the viewfinder and delaying shutter firing. Camera shake can blur the image and the subject (which might have moved) cannot be seen at the instant of exposure. A fixed semi-transparent pellicle reflex mirror, reflecting 30% of the light to the viewfinder and transmitting 70% to the film, prevents camera shake and viewfinder blackout, and reduces shutter lag time at the costs of a dimmer viewfinder image, longer exposure times and possible image quality loss. Modern instant return mirrors are fast enough and have efficient enough shock damping systems that the trade offs are not usually considered worthwhile. Pellicle mirror SLRs are very rare and are usually specialized designs for ultra-high speed (10+ frames per second) sequence shooting.

• 1966: Konica Autorex (Japan; called AutoReflex in USA): first SLR with successful shutter-priority (first with focal plane shutter) autoexposure. Most unusually, it allowed selection between frame sizes (horizontal 24×36 mm or vertical 18×24 mm) between frames on the same roll of film. Used mechanical trap-needle autoexposure system controlled by external CdS meter.

• 1967: Zeiss Ikon Contarex Electronic (West Germany): first SLR with electronically controlled focal plane shutter. Had interchangeable film backs, a feature common with medium format SLRs and used in 35mm rangefinder cameras, but unique to Contarex/Contaflex series among 35 mm SLRs. Although Contarex SLRs and their Zeiss lenses were of extremely high quality, they were also extremely expensive and of idiosyncratic (even clumsy) handling.

• 1968: Konica Autoreflex T (Japan): first SLR with internal open aperture TTL metering autoexposure (mechanical shutter-priority).

• 1968: Kodak Instamatic Reflex (USA/Germany): first Kodapak 126 Instamatic film SLR, first camera with electronically controlled autoexposure. Took 26.5×26.5 mm frames on paper-backed, singly-perforated, 35 mm wide film pre-threaded into double-ended cartridge with film supply and take-up spools. Was leaf shutter design with autoexposure system coupled to external metering cell. Accepted excellent Kodak Retina Reflex 35 mm leaf shutter SLR interchangeable lenses. Drop-in loading 126 film was introduced in 1963 as Kodak's first attempt (of many) to solve the problem of amateurs' difficulty in loading 135 film manually. It was briefly an extremely popular amateur non-SLR format, but almost dead by 1972.

• 1970: Minolta SPM (Japan): first Japanese SLR with built-in electric motor drive.

• 1970: Yashica TL-Electro X (Japan): first SLR with all solid-state electronic light metering system.

• 1970: Mamiya RB 67 (Japan): first 67 medium format system SLR. Took ten exposures of 2¼×2¾ inch (6×7 cm) nominal frames (56×69.5 mm actual frames) on 120 film.

• 1970: Mamiya M645 (Japan): first 645 medium format system SLR. Took fifteen exposures of 2¼×1⅝ inch (6×4.5 cm) nominal frames (56×41.5 mm actual frames) on 120 film.

• 1971: Asahi SMC Takumar lenses (Japan): first multicoated (Super-Multi-Coated) lenses for consumer cameras; for M42 screw mount Asahi Pentax SLRs. Lenses with glass elements "single-coated" with a very thin layer of magnesium or calcium fluoride to suppress flare producing surface reflections became common for high-end cameras by 1960. Coating lenses with up to a dozen different layers of chemicals to suppress reflections across the visual spectrum (instead of at only one compromise wavelength) was a logical progression.

• 1971: Asahi Pentax Electro Spotmatic (Japan; called Honeywell Pentax ES in USA): first SLR with electronic aperture-priority (using stop-down TTL metering) autoexposure plus electronically controlled shutter. Earlier mechanical AE systems tended to be unreliable, but reliable and convenient AE systems (as well as other electronic control systems) that electronically set either the camera shutter speed or lens aperture from light meter readings once the other was manually set began with the Electro Spotmatic. Rival electronic AE SLRs included the Canon EF (1973; shutter priority), Minolta XE–7 (1972; aperture priority) and Nikkormat EL (1972; aperture priority), all from Japan. Electronic AE came to most 35 mm SLRs by the late 1970s. The electronic AE SLR also killed the German camera industry when the Germans failed to keep up with the Japanese. After ailing throughout the 1960s, such famous nameplates as Contax, Exakta, Leica, Rollei and Voigtländer went bankrupt, were sold off, contracted production to East Asia or became boutique brands in the 1970s.

• 1971: Praktica LLC (East Germany): first interchangeable lens camera with electric contact lens mount, first camera with electric lens diaphragm stopdown control. Had M42 screw mount modified for open aperture metering. The M42 mount was a very popular interchangeable lens mount for a quarter century. It was used by almost two dozen different SLR brands, most notably Asahi Pentax. (Asahi became so closely associated with it that it was often erroneously called the Pentax screw mount.) However, by the early 1970s, the M42's limitations, especially no provision for auto-diaphragm lens open aperture viewing and metering, were becoming serious liabilities. After unpopular and uncoordinated attempts to modify the screw mount to support auto-diaphragm lenses, Asahi abandoned the M42 mount in 1975, effectively killing it.

• 1972: Polaroid SX-70 (USA): first instant film SLR. Had non-pentaprism mirror reflex system and electronic autoexposure in flat-folding body with bellows and fixed 116 mm f/8 lens. Took ten exposure, 3⅛×3⅛ inch frame Polaroid SX-70 instant film packs. The principle of self-developing "instant photography" came to Edwin Land in 1943. The first production instant camera was the non-SLR Polaroid Land Model 95 (USA) of 1948, producing sepia-toned, peel-apart pictures. Steady improvements culminated in SX-70 type full-color, self-contained, develop-before-your-eyes, "garbage-free" prints.

• 1972: Olympus OM-1 (quickly changed from M-1 when E. Leitz objected; Japan): first compact 35 mm SLR. At 510g, about two thirds the weight of most earlier 35 mm SLRs. Excellent mechanical design with excellent interchangeable lenses and large accessory system.

• 1974: Vivitar Series 1 70–210mm f/3.5 (USA/Japan): first professional-level quality macro zoom lens for 35 mm SLRs. Early zoom lenses often had very inferior optical quality compared to prime lenses, but improvements in zoom lens design and construction made zooms normal on virtually all but the most expensive still cameras by 1990.

• 1976: Canon AE-1 (Japan): first SLR with microprocessor electronics. Well integrated and compact shutter-priority autoexposure design with excellent interchangeable lenses and large accessory system. Sold five million units and immediately made the 35 mm SLR a popular amateur camera.

• 1976: Olympus OM-2 (Japan): first SLR with TTL, off-the-film (OTF) flash autoexposure. Manual flash exposure control for a natural look is complex and convenient TTL autoflash metering became standard in virtually all SLRs by the mid 1980s.

• 1976 Minolta 110 Zoom SLR (Japan): first Pocket Instamatic 110 film SLR. Had built-in zoom lens (fixed 25–50 mm f/4.5 Zoom Rokkor-Macro). Took up to 24 exposures of 13×17 mm frames on paper-backed, singly-perforated, 16 mm wide film pre-threaded into double-ended cartridge with film supply and take-up spools. Compact, drop-in loading 110 film was introduced by Kodak in 1972. It was briefly an extremely popular amateur non-SLR format but almost dead by 1982.

• 1977: Minolta XD11 (Japan; called XD7 in Europe, XD in Japan): first dual mode autoexposure SLR. Had both aperture-priority and shutter-priority autoexposure.

• 1978: Polaroid SX-70 Sonar OneStep (USA): first electronic autofocus SLR. Had active ultrasonic sonar echo-location rangefinder AF system. This unique-to-Polaroid AF system had no influence on any other type of AF SLR. Took ten exposure, 3⅛×3⅛ inch frame, Polaroid Time-Zero SX-70 instant film packs.

• 1978: Konica FS-1 (Japan): first SLR with built-in motorized autoloading. Also had autowinding, but not auto-rewind. A photographer's great dislike (and Kodak bugbear) of 135 film was the need to manually thread the film leader into the camera's take-up spool and built-in, motorized, automatic film-handling systems became normal in virtually all 35 mm SLRs by late 1980s. This is, of course, a non-issue in modern digital SLRs.

• 1978: Asahi Pentax Auto 110 (Japan): first interchangeable lens Pocket Instamatic 110 film system SLR. Mini-35mm SLR-like autoexposure design with good interchangeable lenses and large accessory system. Was smallest and lightest SLR ever made – 2.2×3.9×1.8 inch, 5.6 ounce with Pentax-110 24 mm f/2.8 lens.

• 1978: Canon A-1 (Japan): first camera with 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 (focus), the A-1 had a microprocessor computer programmed to automatically select a compromise exposure from light meter input. Virtually all cameras had some sort of program mode or modes by the mid-1980s. It was also the first camera to have all four of the now standard PASM (program/aperture-priority/shutter-priority/manual) exposure modes. Canon's long term emphasis on the highest possible technology eventually allowed the company to dominate the 35 mm SLR market; first at the amateur level, with their AE-1 (see above) and A-1, and then (despite a stumble in the mid 1980s when they came late to autofocus) the professional level in the early 1990s with the Canon EOS-1 (Japan) of 1989.

• 1979 Pentax ME Super (Japan): first SLR with primarily electronic push button controls. Had increase/decrease push buttons for shutter speed selection instead of a traditional shutter speed dial.

• 1980: Ricoh XR-7 and XR-S (Japan): first SLR with viewfinder LCD. LCD showed pseudo-meter needle pointing along a shutter speed scale to indicate light meter recommended settings.

• 1980: Nikon F3 (Japan): first SLR with viewfinder LCD digital data display. LCD only showed shutter speeds. As computerized SLR features multiplied, comprehensive viewfinder LCD displays became normal in virtually all 35 mm SLRs by the late 1980s.

• 1981: Pentax ME F (Japan): first built-in autofocus 35 mm SLR. Had passive contrast detection AF system. Autofocused poorly and was not commercially successful. Also had Pentax K-F mount, the first electric contact bayonet lens mount for interchangeable lens cameras. It was used only by the Pentax ME F body and SMC Pentax AF 35mm-70mm f/2.8 Zoom Lens.

• 1982: Polaroid SLR 680 (USA): first SLR with built-in electronic flash. Had active sonar AF system. Took ten exposure, 3⅛×3⅛ inch frame Polaroid 600 instant film packs. Was improved Polaroid SX-70 Sonar AF SLR with almost-all plastic (acrylonitrile butadiene styrene (ABS)) body, built-in flash and faster film. The SLR 680 represents the zenith of instant photography and was the finest instant camera ever made. The popularity of instant photography waned throughout the 1980s as auto-everything 35 mm point-and-shoot cameras and fast one-hour film developing became common.

• 1983: Pentax Super A (Japan; called Super Program in USA): first SLR with external LCD data display. With push buttons for shutter speed selection instead of a shutter speed dial, Super Program used an LCD to show set shutter speed. As computerized SLR features multiplied, large external LCD panels became normal on virtually all 35 mm SLRs by the late 1980s.

• 1983: Nikon FA (Japan): first camera with multi-segmented (or matrix or evaluative; called Automatic Multi-Pattern) light meter. Had a built-in computer to analyze light levels in different segments of the field of view for convenient exposure control in difficult lighting situations. Earlier metering systems could be fooled 10+% of the time, and matrix metering systems became virtually standard in 35 mm SLRs by 1990. Modern matrix meters are virtually 100% technically accurate, although the photographer may wish to alter the settings for artistic purposes.

• 1983: Olympus OM-4 (Japan): first camera with built-in spot-meter (2% of view; 3.3º with 50 mm lens). Meter could measure eight individual spots and average them for precise exposure control in difficult lighting situations. Spotmeters versus matrix meters represent the opposite ends of the light meter spectrum: fully manual contemplative metering versus completely computerized instantaneous metering.

• 1985: Minolta Alpha 7000 (Japan; called Maxxum 7000 in USA): first commercially successful autofocus 35 mm SLR, first passive phase comparison AF SLR, first system AF SLR, first SLR with built-in motorized auto-rewind. Well integrated PASM autoexposure and built-in motor winder design with very good interchangeable lenses and large accessory system. Ever since the first autofocus camera, the non-SLR Konica C35 AF 35 mm P/S of 1977 (with its built-in passive electronic rangefinder system), AF had been common in 35 mm point-and-shoot cameras. The phenomenal success of the Maxxum immediately made the AF SLR the dominant 35 mm SLR type.

• 1987: Pentax SFX (Japan; called SF1 in USA): first 35 mm SLR with built-in electronic flash. Built-in flashes for convenient auxiliary light in dim situations or for fill-light in high contrast situations had been common on point-and-shoot cameras since the mid 1970s and became standard on all but the most expensive cameras by the early 1990s.

• 1987: Canon EF mount (Japan): first all-electronic contact camera lens mount for interchangeable lens cameras. Introduced by Canon EOS 650 and EOS 620 SLR bodies and Canon EF lenses. Mechanical camera-to-lens linkages can link auto-diaphragm lenses and instant return mirror, focal plane shutter SLRs, but electronic autofocus required additional electronic controls. Canon decided to place everything under electronic control, even though it meant that earlier Canon lenses would not be usable with the new bodies.

• 1989 Yashica Samurai Z-L (Japan): first SLR intentionally designed for left-handed operation. Took up to 72 exposures of horizontal 18×24 mm single frames (also called half frames) on 135 type film. Had fixed autofocus 25–75 mm f/4–5.6 zoom lens, built-in motor drive and electronic flash. Was mirror copy of auto-everything, point-and-shoot Samurai Z camera.

• 1991: Kodak Digital Camera System DCS (USA/Japan): first digital still capture SLR. Heavily modified Nikon F3 35 mm SLR and MD-4 motor drive with 1024×1280 pixel (1.3 MP) charge-coupled-device (CCD) sensor, 8 MB DRAM memory and 200 MB tethered hard drive. Used manual focus Nikon F mount lenses with 2× lens field of view factor compared to standard 135 film. List price was US$19,995 (standard Nikon F3HP was US$1295 list; MD-4, US$485). Digital still (then called still video) photography first demonstrated in original Sony Mavica (Japan) prototype camera in 1981. Digital photography did not in any way alter the basic focal plane shutter, instant return mirror, pentaprism, and auto-diaphragm lens formula of SLR camera design developed over the previous century.

• 1992: Nikonos RS (Japan): first waterproof 35 mm system SLR for 100 m maximum depth, underwater diving use. Had autofocus, autoexposure, TTL autoflash, excellent interchangeable lenses and good accessory system.

• 1996: Minolta Vectis S-1 (Japan/Malaysia): first APS IX240 film SLR. Took up to forty exposures of 16.7×30.2 mm frames on polyethylene napthalate base, singly-perforated 24 mm wide film coated with invisible magnetic data encoding stripe, pre-loaded into self-locking ready-to-use cartridges. Had flat-topped non-pentaprism sideways mirror reflex and optical relay viewfinder. Compact design with good lenses and large accessory system. APS cameras were introduced by Kodak, Canon, Fuji, Minolta and Nikon in 1996 as Kodak's last attempt (of many) at drop-in film loading. APS failed because, with motorized autoloading perfected, manual 135 film loading was not an issue anymore; because it was more expensive than 135, without any compelling offsetting benefits and because the late 1990s was when digital photography was gaining momentum. APS was never very popular and was almost dead by 2002.

• 2003: Canon EOS 300D (Japan; called EOS Digital Rebel in USA): first sub-US$1000 high-resolution digital SLR. Well integrated focal plane shutter, instant return mirror, pentaprism, auto-diaphragm, autoexposure, matrix-metering, autofocus, built-in autoflash, computer-controlled design with excellent lenses and good accessory system. Took up to 2048×3072 pixel (6.3 MP) digital images using a 15.1×22.7 mm complementary metal-oxide-semiconductor (CMOS) sensor (1.6× lens factor). With an original list price of US$899 (body only; US$999 with 18-55 mm f/3.5-5.6 Canon EF-S zoom lens), it sold 1.2 million units in eighteen months and was primarily responsible for digital SLR sales vaulting past film SLR sales in the USA in 2004.

See also

• Category:SLR cameras
• Twin-lens reflex camera
• View camera
• Box camera
• Rangefinder camera
• Zeiss Ikon
• Digital SLR

External links and sources

• Spira, S. F. The History of Photography as Seen through the Spira Collection. New York: Aperture, 2001. ISBN 0-89381-953-0.
• Photography in Malaysia's Contax History, Part II.
• Digital Lens Multiplier Effect Calculator Calculate the Field of View of a 35mm lens when used on a digital SLR
• SLR Today