<P> Large format SLR cameras were probably first marketed with the introduction of C.R. Smith's Monocular Duplex (U.S., 1884). SLRs for smaller exposure formats were launched in the 1920s by several camera makers . The first 35mm SLR available to the mass market, Leica's PLOOT reflex housing along with a 200mm f4. 5 lens paired to a 35mm rangefinder camera body, debuted in 1935 . The Soviet Спорт ("Sport"), also a 24mm by 36mm image size, was prototyped in 1934 and went to market in 1937 . K. Nüchterlein's Kine Exakta (Germany, 1936) was the first integrated 35mm SLR to enter the market . Additional Exakta models, all with waist - level finders, were produced up to and during World War II . Another ancestor of the modern SLR camera was the Swiss - made Alpa, which was innovative, and influenced the later Japanese cameras . The first eye - level SLR viewfinder was patented in 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 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 . </P> <P> The first commercially produced SLR that employed a roof pentaprism was the Italian Rectaflex A. 1000, shown in full working condition on Milan fair April 1948 and produced from September the same year, thus being on the market one year before the east German Zeiss Ikon VEB Contax S, announced on May 20, 1949, produced from September . </P> <P> The Japanese adopted and further developed the SLR . In 1952, Asahi developed the Asahiflex and in 1954, the Asahiflex IIB . In 1957, the Asahi Pentax combined the 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). </P> <P> As a small matter of history, the first 35 mm camera (non-SLR) to feature through the lens light metering may have been Nikon, with a prototype rangefinder camera, the SPX . According to the website below, the camera used Nikon' S' type rangefinder lenses . </P>

Which type of cameras do not have mirrors inside them