In photography, the

single-lens reflex camera A single-lens reflex camera (SLR) is a camera that typically uses a mirror and prism system (hence "reflex" from the mirror's reflection) that permits the photographer to view through the lens and see exactly what will be captured. With twin l ...

(SLR) is provided with a mirror to redirect light from the picture taking lens to the

viewfinder In photography, a viewfinder is what the photographer looks through to compose, and, in many cases, to focus the picture. Most viewfinders are separate, and suffer parallax, while the single-lens reflex camera lets the viewfinder use the main ...

prior to releasing the shutter for composing and

focusing Focusing may refer to: * Adjusting an optical system to minimize defocus aberration * Focusing (psychotherapy), a psychotherapeutic technique See also *Focus (disambiguation) Focus, or its plural form foci may refer to: Arts * Focus or Focus Fe ...

an image. When the shutter is released, the mirror swings up and away allowing the exposure of the photographic medium and instantly returns after the exposure. No SLR camera before 1954 had this feature, although the mirror on some early SLR cameras was entirely operated by the force exerted on the shutter release and only returned when the finger pressure was released. The Asahiflex II, released by Japanese company Asahi (

Pentax is a brand name used primarily by the Japanese multinational imaging and electronics company Ricoh for DSLR cameras, lenses, sport optics (including binoculars and rifle scopes), and CCTV optics. The Pentax brand is also used by Hoya Corpora ...

) in 1954, was the world's first SLR camera with an instant return mirror.Michael R. Peres (2013)
''The Focal Encyclopedia of Photography'', page 779

Taylor & Francis Taylor & Francis Group is an international company originating in England that publishes books and academic journals. Its parts include Taylor & Francis, Routledge, F1000 Research or Dovepress. It is a division of Informa plc, a United Ki ...

References

{{reflist 135 film cameras SLR cameras Japanese inventions