Editing Single-lens reflex camera (section)

== Shutter mechanisms ==
{{Main|Shutter (photography)}}

Almost all contemporary SLRs use a [[focal-plane shutter]] located in front of the film plane, which prevents the light from reaching the film even if the lens is removed, except when the shutter is actually released during the exposure. There are various designs for focal plane shutters. Early focal-plane shutters designed from the 1930s onwards usually consisted of two curtains that travelled horizontally across the film gate: an opening shutter curtain followed by a closing shutter curtain. During fast shutter speeds, the focal-plane shutter would form a 'slit' whereby the second shutter curtain was closely following the first opening shutter curtain to produce a narrow, vertical opening, with the shutter slit moving horizontally. The slit would get narrower as shutter speeds were increased. Initially these shutters were made from a cloth material (which was in later years often rubberised), but some manufacturers used other materials instead. Nippon Kōgaku (now [[Nikon Corporation]]), for example, used [[titanium]] foil shutters for several of their flagship SLR cameras, including the [[Nikon F]], [[Nikon F2|F2]], and [[Nikon F3|F3]].

Other focal-plane shutter designs, such as the [[Nidec Copal Corporation|Copal]] Square, travelled vertically&nbsp;— the shorter travelling distance of 24 millimetres (as opposed to 36&nbsp;mm horizontally) meant that minimum exposure and flash synchronisation times could be reduced. These shutters are usually manufactured from metal, and use the same moving-slit principle as horizontally travelling shutters. They differ, though, in usually being formed of several slats or blades, rather than single curtains as with horizontal designs, as there is rarely enough room above and below the frame for a one-piece shutter. Vertical shutters became very common in the 1980s (though [[Konica]], [[Mamiya]], and Copal first pioneered their use in the 1950s and 1960s, and are almost exclusively used for new cameras. Nikon used Copal-made vertical plane shutters in their Nikomat/Nikkormat -range, enabling x-sync speeds from {{frac|1|30}} to {{frac|1|125}} while the only choice for focal plane shutters at that time was {{frac|1|60}}. Later, Nikon again pioneered the use of titanium for vertical shutters, using a special honeycomb pattern on the blades to reduce their weight and achieve world-record speeds in 1982 of {{frac|1|4000}} second for non-sync shooting, and {{frac|1|250}} with x-sync. Nowadays most such shutters are manufactured from cheaper aluminium (though some high-end cameras use materials such as [[carbon-fibre]] and [[Kevlar]]).

Another shutter system is the [[leaf shutter]], whereby the shutter is constructed of diaphragm-like blades and can be situated either between the lens or behind the lens. If the shutter is part of a lens assembly some other mechanism is required to ensure that no light reaches the film between exposures. An example of a behind-the-lens leaf shutter is found in the 35&nbsp;mm SLRs produced by [[Kodak]], with their Retina Reflex camera line; Topcon, with their Auto 100; and Kowa with their SE-R and SET-R reflexes. A primary example of a medium-format SLR with a between-the-lens leaf shutter system would be [[Hasselblad]], with their 500C, 500&nbsp;cm, 500 EL-M (a motorized Hasselblad) and other models (producing a 6&nbsp;cm square negative). Hasselblads use an auxiliary shutter blind situated behind the lens mount and the mirror system to prevent the fogging of film. Other medium-format SLRs also using leaf shutters include the now discontinued Zenza-Bronica camera system lines such as the Bronica ETRs, the ETRs'i (both producing a 6&nbsp;×&nbsp;4.5&nbsp;cm. image), the SQ and the SQ-AI (producing a 6&nbsp;×&nbsp;6&nbsp;cm image like the Hasselblad), and the Zenza-Bronica G system (6&nbsp;×&nbsp;7&nbsp;cm). Certain Mamiya medium-format SLRs, discontinued camera systems such as the Kowa 6 and a few other camera models also used between-the-lens leaf shutters in their lens systems. Thus, any time a photographer purchased one of these lenses, that lens included a leaf shutter in its lens mount. Because leaf shutters synchronized electronic flash at all shutter speeds especially at fast shutter speeds of {{frac|1|500}} of a second or faster, cameras using leaf shutters were more desirable to studio photographers who used sophisticated studio electronic flash systems. Some manufacturers of medium-format [[120 film]] SLR cameras also made leaf-shutter lenses for their focal-plane-shutter models. Rollei made at least two such lenses for their Rolleiflex SL-66 medium format which was a focal-plane shutter SLR. Rollei later switched to a camera system of leaf-shutter design (e.g., the 6006 and 6008 reflexes) and their current medium-format SLRs are now all of the between-the-lens shutter design.