The history of the single-lens reflex camera (SLR) begins with the use of a reflex mirror in a camera obscura described in 1676, but it took a long time for the design to succeed for photographic cameras. The first patent was granted in 1861, and the first cameras were produced in 1884, but while elegantly simple in concept, they were very complex in practice. One by one these complexities were overcome as optical and mechanical technology advanced, and in the 1960s the SLR camera became the preferred design for many high-end camera formats.

The advent of digital point-and-shoot cameras in the 1990s through the 2010s with LCD viewfinder displays reduced the appeal of the SLR for the low end of the market, and in the 2010s and 2020s smartphones have taken this place. The SLR remained the camera design of choice for mid-range photographers, ambitious amateur and professional photographers well into the 2010s, but by the 2020s had become greatly challenged if not largely superseded by the mirrorless interchangeable-lens camera, with notable brands such as Nikon and Canon having stopped releasing new flagship DSLR cameras for several years in order to focus on mirrorless designs.

Early large and medium format SLRs

The photographic single-lens reflex camera (SLR) was invented in 1861 by Thomas Sutton, a photography author and camera inventor who ran a photography related company together with Louis Désiré Blanquart-Evrard on Jersey. Only a few of his SLRs were made. The first production SLR with a brand name was Calvin Rae Smith's Monocular Duplex (USA, 1884). Other early SLR cameras were constructed, for example, by Louis van Neck (Belgium, 1889), Thomas Rudolphus Dallmeyer (England, 1894) and Max Steckelmann (Germany, 1896), and Graflex of the United States and Konishi in Japan produced SLR cameras as early as 1898 and 1907 respectively. These first SLRs were large format cameras.Rudolf Kingslake: The Photographic Manufacturing Companies of Rochester, New York, p. 21Konishi: Sakura Reflex Prano; source The Japanese Historical Camera, p. 5 While SLR cameras were not very popular at the time, they proved useful for some work. These cameras were used at waist level; the ground glass screen was viewed directly, using a large hood to keep out extraneous light. In most cases, the mirror had to be raised manually as a separate operation before the shutter could be operated.

As with camera technology in general, SLR cameras became available in smaller and smaller sizes. Medium format SLRs soon became common, at first larger box cameras and later "pocketable" models such as the Ihagee Vest-Pocket Exakta of 1933.

Development of the 35 mm SLR

The first 35mm prototype SLR was the "Filmanka" developed in 1931 by A. Min in the Soviet Union.Proletarskoe Foto, No. 3, 1933 In 1933 A.O. Gelgar developed the "GelVeta" also in the USSR, later renamed Спорт ("Sport").A. O. Gelgar's Sport "Sport" was a very smart design with a 24mm × 36mm frame size, but, according to some sources, it did not enter the market until 1937, although there is now some evidence emerging that "Sport" may have been in limited production before 1936. Because of the probable production in small numbers it has been claimed not to be the first mass-produced 35mm SLR.

Early innovations Early 35 mm SLR cameras had functionality that was similar to larger models, with a waist-level ground-glass viewfinder and a mirror that remained in the taking position and blacked out the viewfinder after an exposure, and then returned when the film was wound on. Innovations that transformed the SLR were the pentaprism eye-level viewfinder and the instant-return mirror—the mirror flipped briefly up during exposure, immediately returning to the viewfinding position. The half-silvered fixed pellicle mirror, without even the brief blackout of the instant-return mirror, was also innovative but did not become standard. Through-the-lens light metering was another important advance. As electronics advanced, new functionality, discussed below, became available.

Exakta

The first 35mm format SLR in large scale production was the Ihagee Kine Exakta, produced in 1936 in Germany, which was fundamentally a scaled-down Vest-Pocket Exakta. This camera used a waist-level finder.

Various other models were produced, such as the Kine-Exakta, the Exakta II, the Exakta Varex (featuring an interchangeable pentaprism eye-level viewfinder and identified in the United States as the 'Exakta V'), the Exakta Varex VX (identified in the United States as the 'Exakta VX'), the Exakta VX IIa, the Exakta VX IIb, the Exakta VX500 and the Exakta VX1000. Ihagee also manufactured less expensive cameras under the 'Exa' camera label, such as the Exa, the Exa Ia, the Exa II, the Exa IIa, the Exa IIb (which was generally not considered part of the "official" Exa line), and the Exa 500. The Exacta sold well and triggered other camera manufacturers to develop 35mm SLRs. Sales were particularly strong in the medical and scientific fields. A large range of lenses and accessories were made by a variety of manufacturers, turning the camera into one of the first system cameras, although motor drives and bulk loading backs were never produced by Ihagee.

Rectaflex Rectaflex was the name of an Italian camera maker from 1947 to 1958. It was also the name of their sole model. The Rectaflex was a 35 mm SLR camera with a focal plane shutter, interchangeable lenses, and a pentaprism eye-level finder. Rectaflex (followed by Contax S) was the first SLR camera introducing the modern pentaprism eye-level finder. The first prototype (Rectaflex 947) was presented in 1947, with a final presentation in April 1948 and start of series production (A 1000) in September the same year, thus hitting the market one year before the Contax S, presented in 1949. Both were preceded by Alpa-Reflex, first presented to a wider public in April 1944 at the Swiss Trade Fair in Basel (Schweizer Mustermesse). Alpa's production was slow up to 1945, and it lacked a pentaprism, so the image was reversed left-to-right.

Zeiss Zeiss had begun work on a 35mm SLR camera in 1936 or 1937. This camera used an eye-level pentaprism, which allowed eye-level-viewing of an image oriented correctly from left to right. Waist-level finders, however, showed a reversed image, which the photographer had to mentally adjust for while composing the image by looking downward and viewing and focusing. To brighten the viewfinder image, Zeiss incorporated a fresnel lens in between the ground-glass screen and the pentaprism. This design principle became the conventional SLR design used today.

World War II intervened, and the Zeiss SLR did not emerge as a production camera until Zeiss, in the newly created factory in East Germany, introduced the Contax S in 1949, with production ending in 1951. The Italian Rectaflex, series 1000 went into series production the year before, in September 1948, thus being market-ready one year before the Contax. Both were historic progenitors of many later SLRs that adopted this arrangement.

Praktiflex Praktica In 1939, Kamerawerk Niedersedlitz Dresden presented the Praktiflex at the Leipzig spring fair. The camera was a waist type with an M40x1 screw mount and a horizontal cloth focal shutter. This camera is the pattern for most of the 35 mm SLR cameras and also for the Japanese and the digital SLR cameras today. After the war, Praktiflex was the most manufactured 35 mm SLR in Dresden, especially for the Russians as reparations. KW changed to the M42 screw mount invented at Zeiss for Contax S—later used by Pentax, Yashica and others to become a near universal mount. In 1949, it was redesigned with longer shutter speeds, and the name was changed to Praktica. In 1958, KW Niedersedlitz became a part of the VEB Kamer und Kinowerk (old Zeiss), later VEB Pentacon. Praktica was typically a consumer/amateur camera. Many developments were added. It was produced until 2000.

1949 Praktica until Praktica V 1964 Praktica Nova 1969 Praktica L with vertical metal focal plane shutter 1979 Praktica B with new bayonet mount

Highlights: 1956 Praktica FX2 2. version with full automatic internal aperture activator, world standard for more than 20 years. 1959 Praktica IV with permanent eye-level pentaprism. 1964 Praktica V with instant return mirror. 1965 Praktica Mat first European TTL semiautomatic (work aperture) in production 1966 Praktica Super TL with centerweighted TTL 1969 Praktica LLC world first camera with electric simulation of aperture

From 1952 to 1960 the KW factory/VEB Pentacon also produced the Praktina, a system SLR camera for professionals and advanced amateurs with a bayonet mount and focal shutter, but production was closed, partly for political reasons. Praktica was the camera that could be sold outside the DDR and bring foreign currency to the country.

Edixa Another German manufacturer, Edixa was a brand of camera manufactured by Wirgin Kamera Werk, based in Wiesbaden, West Germany. This company's product line included 35mm SLR cameras such as the Edixa Reflex, which featured a Steinel 55mm f/1.9 Quindon lens and an Isco Traegan 50mm f/2.8 lens, the Edixamat Reflex, the Edixa REX TTL, and the Edixa Electronica. The removable pentaprism could be swapped for a waistlevel viewfinder with a pop up magnifier. The lens mount was the same screw thread as the Praktica.

Rise of the Japanese SLRs The earliest Japanese SLR for roll film was perhaps the Baby Super Flex (or Super Flex Baby), a 127 camera made by Umemoto and distributed by Kikōdō from 1938.The Japanese Historical Camera, p. 35 This camera had a leaf shutter, but two years later came the Shinkoflex, a 6×6 camera made by Yamashita Shōkai, with a focal-plane shutter and interchangeable lenses.The Japanese Historical Camera, p. 40 However, Japanese camera makers concentrated on rangefinder and twin-lens reflex cameras (as well as simpler viewfinder cameras), similar to those of the Western makers.

Pentax

The Asahi Optical Company took a different manufacturing path, inspired by the German SLRs. Its first model, the Asahiflex I, existed in prototype form in 1951 and production in 1952, making it the first Japanese-built 35mm SLR. The Asahiflex IIB of 1954 was the first Japanese SLR with an instant-return mirror. Previously, the mirror would remain up and the viewfinder black until the user released the shutter button. In 1957, the Asahi Pentax became the first Japanese fixed-pentaprism SLR; its success led Asahi to eventually rename itself Pentax. This was the first SLR to use the right-hand single-stroke film advance lever of the Leica M3 of 1954 and Nikon S2 of 1955. Asahi (starting with the Asahi Pentax) and many other camera makers used the M42 lens mount from the Contax S, which came to be called the Pentax screw mount. Pentax is now part of Ricoh.

Miranda Orion's (later name-changed to Miranda's) Miranda SLR camera was sold in Japan from August 1955 with the launch of the Miranda T camera. The camera was narrowly the first Japanese-made pentaprism 35mm SLR. It featured a removable pentaprism for eye-level viewing that could be removed for use as a waist-level finder.

Yashica The Yashica Company introduced its own SLR in 1959, the Pentamatic, an advanced, modern 35mm SLR camera with a proprietary bayonet-mount. The Pentamatic featured an automatic stop-down diaphragm (offered only with the Auto Yashinon 50mm/1.8 lens), instant-return mirror, a fixed pentaprism, and a mechanical focal-plane shutter with speeds of 1-1/1000 second, along with additional interchangeable lenses.

Zunow