![Camera shutter 1875 by A A Pearson, Leeds City Museum](https://upload.wikimedia.org/wikipedia/commons/a/af/Camera_shutter_1875_by_A_A_Pearson%2C_Leeds_City_Museum.jpg)
In
photography
Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employed ...
, a shutter is a device that allows light to pass for a determined period, exposing
photographic film
Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin photographic emulsion, emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of th ...
or a
photosensitive Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light. In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicity. ...
digital sensor
A digital sensor is an electronic or electrochemical sensor, where data is digitally converted and transmitted. Sensors are often used for analytical measurements, e.g. the measurement of chemical and physical properties of liquids. Typical measur ...
to light in order to capture a permanent image of a scene. A shutter can also be used to allow pulses of light to pass outwards, as seen in a
movie projector
A movie projector is an optics, opto-mechanics, mechanical device for displaying Film, motion picture film by projecting it onto a movie screen, screen. Most of the optical and mechanical elements, except for the illumination and sound devices ...
or a
signal lamp
Signal lamp training during World War II
A signal lamp (sometimes called an Aldis lamp or a Morse lamp) is a semaphore system using a visual signaling device for optical communication, typically using Morse code. The idea of flashing dots and ...
. A shutter of variable speed is used to control exposure time of the film. The shutter is constructed so that it automatically closes after a certain required time interval. The speed of the shutter is controlled by a ring outside the camera, on which various timings are marked.
Camera shutter
Camera shutters can be fitted in several positions:
*
Leaf shutters are usually fitted within a lens assembly (''central shutter''), or more rarely immediately behind (''behind-the-lens shutter'') or, even more rarely, in front of a lens, and shut off the beam of light where it is narrow.
*
Focal-plane shutter
In camera design, a focal-plane shutter (FPS) is a type of photographic shutter that is positioned immediately in front of the focal plane of the camera, that is, right in front of the photographic film or image sensor.
Two-curtain shutters ...
s are mounted near the
focal plane
In Gaussian optics, the cardinal points consist of three pairs of points located on the optical axis of a rotationally symmetric, focal, optical system. These are the '' focal points'', the principal points, and the nodal points. For ''ideal'' ...
and move to uncover the film or sensor.
Behind-the-lens shutters were used in some cameras with limited lens interchangeability. Shutters in front of the lens, sometimes simply a
lens cap
A lens cover or lens cap provides protection from scratches and minor collisions for camera and camcorder lenses. Lens covers come standard with most cameras and lenses. Some mobile camera phones include lens covers, such as the Sony Ericsson W ...
that is removed and replaced for the long exposures required, were used in the early days of photography. Other mechanisms than the dilating aperture and the sliding curtains have been used; anything which exposes the film to light for a specified time will suffice.
The time for which a shutter remains open (exposure time, often called "shutter speed") is determined by a timing mechanism. These were originally pneumatic (Compound shutter) or
clockwork
Clockwork refers to the inner workings of either mechanical devices called clocks and watches (where it is also called the movement) or other mechanisms that work similarly, using a series of gears driven by a spring or weight.
A clockwork mec ...
, but since the late twentieth century are mostly
electronic
Electronic may refer to:
*Electronics, the science of how to control electric energy in semiconductor
* ''Electronics'' (magazine), a defunct American trade journal
*Electronic storage, the storage of data using an electronic device
*Electronic co ...
. Mechanical shutters typically had a Time setting, where the shutter opened when the button was pressed and remained open until it was pressed again,
Bulb where the shutter remained open as long as the button was pressed (originally actuated by squeezing an actual rubber bulb), and Instantaneous exposure, with settings ranging from 30" to 1/4000" for the best leaf shutters, faster for focal-plane shutters, and more restricted for basic types. The reciprocal of exposure time in seconds is often used for engraving shutter settings. For example, a marking of "250" denotes 1/250". This does not cause confusion in practice.
The exposure time and the effective
aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane.
An opt ...
of the lens must together be such as to allow the right amount of light to reach the film or sensor. Additionally, the exposure time must be suitable to handle any motion of the subject. Usually it must be fast enough to "freeze" rapid motion, unless a controlled degree of
motion blur
Motion blur is the apparent streaking of moving objects in a photograph or a sequence of frames, such as a film or animation. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or lo ...
is desired, for example to give a sensation of movement.
Most shutters have a
flash synchronization
In photography, flash synchronization or flash sync is the synchronizing the firing of a photographic flash with the opening of the shutter admitting light to photographic film or electronic image sensor.
In cameras with mechanical (clockwor ...
switch to trigger a
flash
Flash, flashes, or FLASH may refer to:
Arts, entertainment, and media
Fictional aliases
* Flash (DC Comics character), several DC Comics superheroes with super speed:
** Flash (Barry Allen)
** Flash (Jay Garrick)
** Wally West, the first Kid ...
, if connected. This was quite a complicated matter with mechanical shutters and
flashbulbs which took an appreciable time to reach full brightness, focal-plane shutters making this even more difficult. Special flashbulbs were designed which had a prolonged burn, illuminating the scene for the whole time taken by a focal plane shutter slit to move across the film. These problems were essentially solved for non-focal-plane shutters with the advent of
electronic flash
A flash is a device used in photography that produces a brief burst of light (typically lasting 1/1000 to 1/200 of a second) at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a ...
units which fire virtually instantaneously and emit a very short flash.
When using a focal-plane shutter with a flash, if the shutter is set at its
X-sync
In photography, flash synchronization or flash sync is the synchronizing the firing of a photographic flash with the opening of the shutter admitting light to photographic film or electronic image sensor.
In cameras with mechanical (clockwor ...
speed or slower the whole frame will be exposed when the flash fires (otherwise only a band of the film will be exposed).
Some electronic flashes can produce a longer pulse compatible with a focal-plane shutter operated at much higher shutter speeds. The focal-plane shutter will still impart focal-plane shutter distortions to a rapidly moving subject.
Cinematography
Cinematography (from ancient Greek κίνημα, ''kìnema'' "movement" and γράφειν, ''gràphein'' "to write") is the art of motion picture (and more recently, electronic video camera) photography.
Cinematographers use a lens to focu ...
uses a
rotary disc shutter
A rotary disc shutter is a type of shutter. It is notably used in motion picture cameras. Rotary shutters are semicircular discs that spin in front of the film gate, alternately allowing light from the lens to strike the film, or blocking it.
D ...
in
movie camera
A movie camera (also known as a film camera and cine-camera) is a type of photographic camera that rapidly takes a sequence of photographs, either on an image sensor or onto film stock, in order to produce a moving image to project onto a movie s ...
s, a continuously spinning disc which conceals the image with a reflex mirror during the
intermittent motion between frame exposure. The disc then spins to an open section that exposes the next frame of film while it is held by the
registration pin {{unreferenced, date=January 2014
A registration pin is a device intended to hold a piece of film, paper or other material in place during photographic exposure, copying or drawing.
Registration pins are used in offset printing and cartography, to ...
.
Focal-plane shutter
A focal-plane shutter is positioned just in front of the film, in the
focal plane
In Gaussian optics, the cardinal points consist of three pairs of points located on the optical axis of a rotationally symmetric, focal, optical system. These are the '' focal points'', the principal points, and the nodal points. For ''ideal'' ...
, and moves an aperture across the film until the full frame has been exposed.
Focal-plane shutters are usually implemented as a pair of light-tight cloth, metal, or plastic curtains. For shutter speeds slower than a certain point (known as the X-sync speed of the shutter), which depends on the camera, one curtain of the shutter opens, and the other closes after the correct exposure time. At shutter speeds faster than the X-sync speed, the top curtain of the shutter travels across the focal plane, with the second curtain following behind, effectively moving a slit across the focal plane until each part of the film or sensor has been exposed for the correct time. The effective exposure time can be much shorter than for central shutters, at the cost of some distortion of fast-moving subjects.
Focal plane shutters have the advantage over central leaf shutters of allowing the use of interchangeable lenses without requiring a separate shutter for each lens. (Leaf shutters behind the lens also allow interchanging the lens using a single shutter.)
They have several disadvantages as well:
* Distortion of fast-moving subjects: although no part of the film is exposed for longer than the time set on the dial, one edge of the film is exposed an appreciable time after the other, so that a horizontally moving shutter will, for example, elongate or shorten the image of a car speeding in the same or the opposite direction to the shutter movement.
* They are noisier, which is a detriment to candid and nature photography.
* Their more complex mechanical structure causes a shorter life-span than other shutter designs.
* If a focal-plane shutter camera is left with sunlight falling on the lens (and the mirror up for an SLR), it is possible to burn a hole in the closed curtain of a non-metal shutter.
* Camera shake due to the impact of the larger curtains starting and stopping rapidly. Camera designers have learned to overcome SLR mirror-slap by including a
mirror lock-up
Mirror lock-up (often abbreviated to MLU) is a feature employed in many Single Lens Reflex (SLR) cameras. It allows the operator to reduce vibration-induced motion blur during exposure. It also allows the mounting of lenses which extend into th ...
feature in some cameras. This removes the camera-shake from the large slapping mirror inside the camera, but does not prevent camera-shake caused by the shutter mechanism itself. Mirror-lock-up introduces yet another problem: with the mirror locked-up out of the way the optical viewfinder cannot be used for focussing, framing, or exposure metering. Newer DSLR cameras include a "
live preview
Live preview is a feature that allows a digital camera's display screen to be used as a viewfinder. This provides a means of previewing framing and other exposure before taking the photograph. In most such cameras, the preview is generated by m ...
" where the image from the main imaging sensor is displayed directly on an LCD display, so it is still possible to focus (manually or in newer models by contrast detection) and frame. This prevents most camera shake from the focal-plane shutter, as instead of a first curtain an electronic shutter is used.
Simple leaf shutter
image:leaf shutter.svg, 250px, Simple leaf shutter
1. Shutter plate
2. Aperture covered by leaf shutter
3. Aperture during exposure
4. Leaf blade
5. Catch mechanism
6. Butterfly spring
A ''simple leaf shutter'' is a type of camera shutter consisting of a mechanism with one or more pivoting metal leaves which normally does not allow light through the lens onto the film, but which when triggered opens the shutter by moving the leaves to uncover the lens for the required time to make an exposure, then shuts.
Simple leaf shutters have a single leaf, or two leaves, which pivot so as to allow light through to the lens when triggered. If two leaves are used they have curved edges to create a roughly circular aperture. They typically have only one
shutter speed
In photography, shutter speed or exposure time is the length of time that the film or digital sensor inside the camera is exposed to light (that is, when the camera's shutter (photography), shutter is open) when taking a photograph.
The am ...
and are commonly found in basic cameras, including
disposable camera
A disposable or single-use camera is a simple box camera meant to be used once. Most use fixed-focus lenses. Some are equipped with an integrated flash unit, and there are even waterproof versions for underwater photography. Internally, the camera ...
s. Some have more than one speed. Shutters for newer digital cameras are a combination of electronic and mechanical timings. Some cameras employ a 100% electronic shutter, created by turning on and off the imaging sensor's signals. Digital cameras that can also take video implement this method for their video modes. For single-frame photography then either mechanical or mechanical and electronic methods are used.
Guillotine shutter
In the simplest version of Guillotine shutter a plate with an aperture slides across the lens opening. Simple versions from the 1880s and 1890s were often known as Drop shutters. They worked vertically and were usually powered by a rubber band, a spring or just gravity. Later they were fitted to run horizontally in hand cameras where they were spring powered with spring tension or pneumatic regulation.
Rotating shutter
Hemispheric
The shutter plate consisted of a part of a sphere integrated to rotate behind the lens. It was a type of shutter found on the Photosphere and other cameras.
Diaphragm shutter
A
''diaphragm'' or ''leaf''
shutter (as distinct from the simple leaf shutter above) consists of a number of thin blades which briefly uncover the camera aperture to make the exposure. The blades slide over each other in a way which creates a circular aperture which enlarges as quickly as possible to uncover the whole lens, stays open for the required time, then closes in the same way. The larger the number of blades, the more accurately circular is the aperture.
Flash synchronization
In photography, flash synchronization or flash sync is the synchronizing the firing of a photographic flash with the opening of the shutter admitting light to photographic film or electronic image sensor.
In cameras with mechanical (clockwor ...
is easily achieved with a pair of contacts that close when the shutter is fully open.
Ideally the shutter opens instantaneously, remains open as long as required, and closes instantaneously. This is essentially the case at slower speeds, but as speeds approach their maximum the shutter is far from fully open for a significant part of the exposure time. Effectively the shutter acts as an additional aperture, and may cause an increased
depth of field
The depth of field (DOF) is the distance between the nearest and the furthest objects that are in acceptably sharp focus in an image captured with a camera.
Factors affecting depth of field
For cameras that can only focus on one object dist ...
, undesirable if shallow focus is being used creatively. Or it may cause mechanical vignetting if the diaphragm is outside of the lens (like a focal plane shutter or apodization filter).
The term ''diaphragm shutter'' has also been used to describe an optical stop with a slit, near the focal plane of a moving-film high-speed camera.
A few types and makers of leaf shutters became very well known. The early
Compound shutter
The Compound shutter is a mechanical leaf shutter for photographic camera
A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a ...
had a pneumatic mechanism, with a piston sliding against air resistance in a cylinder. They were quieter at slow speeds than clockwork, but potentially very inaccurate. More accurate clockwork mechanisms then replaced the airbrake, and the German Compur,
and the later Synchro-Compur, became virtually the standard quality shutter. Later the Japanese Copal shutter
The , or Copal, is a Japanese manufacturer of optical, electronic and mechanical equipment, primarily for the photographic industry. It has been a subsidiary of Nidec Corporation since 1998, and was formerly known as the Copal Corporation. The ...
was widely adopted in quality equipment. The German Prontor and Japanese Seikosha shutters were also widely used. ''Up and Down with Compur: The development and photo-historical meaning of leaf shutters'', by Klaus-Eckard Riess, translated by Robert "The Professor" Stoddard[ gives a detailed history and technical description of leaf shutters. The company Compur Monitor was still in business , but made only gas detection systems. Leaf shutters under the Compur, Copal, and Seiko names are no longer manufactured.][
]
Central shutter
A ''central shutter'' is not a type of shutter as such, but describes the position of the shutter: it is typically a leaf shutter
In photography, a shutter is a device that allows light to pass for a determined period, exposing photographic film or a photosensitive digital sensor to light in order to capture a permanent image of a scene. A shutter can also be used to allow ...
(or simple leaf shutter), and located within the lens assembly where a relatively small opening allows light to cover the entire image. Leaf shutters can also be located behind, but near, the lens, allowing lens interchangeability. The alternative to a central or behind-the-lens shutter is a focal-plane shutter
In camera design, a focal-plane shutter (FPS) is a type of photographic shutter that is positioned immediately in front of the focal plane of the camera, that is, right in front of the photographic film or image sensor.
Two-curtain shutters ...
.
Interchangeable-lens cameras with a central shutter within the lens body require that each lens has a shutter built into it. In practice most cameras with interchangeable lenses use a single focal plane shutter in the camera body for all lenses, while cameras with a fixed lens use a central shutter. Many medium-format and most large-format cameras, however, have interchangeable lenses each fitted with a central shutter. A few interchangeable-lens cameras have a behind-the-lens leaf shutter. Large-format press camera
A press camera is a medium or large format view camera that was predominantly used by press photographers in the early to mid-20th century. It was largely replaced for press photography by 35mm film cameras in the 1960s, and subsequently, by dig ...
s often had a focal-plane shutter. Some had both a focal-plane shutter (for lens interchangeability) and a lens with central shutter (for flash synchronisation); one shutter would be locked open.
Film cameras, but not digital cameras, with a central shutter and interchangeable lenses often have a secondary shutter or darkslide to cover the film and allow changing lens in mid-roll without fogging the film.
The main advantages of central and behind-the-lens leaf shutters compared to a focal-plane shutter are:
* Flash synchronization is possible at all speeds because the shutter opens fully, unlike a focal-plane shutter sliding a slit relatively slowly across the film for a short effective exposure.
* Small size is possible as the shutter is placed where the bundle of rays is narrow, either inside or just behind the lens.
* Many versions have no connection between the cocking mechanism and the film advance mechanism, making multiple exposures possible (this can be a disadvantage, as multiple exposures can be produced accidentally if the photographer forgets to advance the film).
* Usually much quieter.
* More realistic photographs in high speed panning—lateral focal plane shutters compress or elongate the image in such cases.
* Longer shutter life.
Some disadvantages of the central shutter are:
* For an interchangeable lens system, each lens has to have a shutter built into it.
* All leaf shutter speeds are limited by the speed at which the leaves can move: typically 1/500th of a second for a high-specification diaphragm shutter and 1/125th of a second for a simple leaf shutter.
* Some versions may have no connection between the cocking mechanism and the film advance mechanism, making accidental multiple exposures a common problem, although this is a feature of camera manufacture rather than the shutter itself.
Electronic shutter
Digital image sensor
An image sensor or imager is a sensor that detects and conveys information used to make an image. It does so by converting the variable attenuation of light waves (as they pass through or reflect off objects) into signals, small bursts of curr ...
s (both CMOS
Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFE ...
and CCD image sensors) can be constructed to give a shutter equivalent function by transferring many pixel cell charges
Charge or charged may refer to:
Arts, entertainment, and media Films
* ''Charge, Zero Emissions/Maximum Speed'', a 2011 documentary
Music
* ''Charge'' (David Ford album)
* ''Charge'' (Machel Montano album)
* '' Charge!!'', an album by The Aqu ...
at one time to a paired shaded double called frame transfer shutter. If the full-frame is transferred at one time, it is a global shutter. Often the shaded cells can independently be read, while the others are again collecting light. Extremely fast shutter operation is possible as there are no moving parts or any serialized data transfers. Global shutter can also be used for videos as a replacement for rotary disc shutter
A rotary disc shutter is a type of shutter. It is notably used in motion picture cameras. Rotary shutters are semicircular discs that spin in front of the film gate, alternately allowing light from the lens to strike the film, or blocking it.
D ...
s.
Image sensors without a shaded full-frame double must use serialized data transfer of illuminated pixels called rolling shutter
Rolling shutter is a method of image capture in which a still picture (in a still camera) or each frame of a video (in a video camera) is captured not by taking a snapshot of the entire scene at a single instant in time but rather by scanning ...
. A rolling shutter scans the image in a line-by-line fashion, so that different lines are exposed at different instants, as in a mechanical focal-plane shutter, so that motion of either camera or subject will cause geometric distortions, such as skew or wobble.
Today, most digital cameras use combination of mechanical shutter and electronic shutter or mechanical shutter solely. Mechanical shutter can accommodate up to 1/16000 seconds (for example the Minolta Dynax/Maxxum/α-9 film camera had a maximum of 1/12000, a record in its era, and the later digital Nikon D1 series were capable of 1/16000), while electronic shutter can accommodate at least 1/32000 seconds, used for many superzoom
A superzoom or ultrazoom lens is a type of photographic zoom lens with unconventionally large focal length factors, typically ranging from wide angle to extreme long lens focal lengths in one lens. There is no clear definition of a superzoom len ...
cameras and currently many Fujifilm APS-C cameras (X-Pro2, X-T1, X100T and others).
Stacked CMOS sensors combine the image sensor itself with ADCs and digital memory in the same package. The readout of these sensors is faster than traditional sensors, because the digitized image is transferred into the digital memory in the sensor itself during readout and only afterwards transferred out of the sensor. This results in an electronic shutter which is as fast as a mechanical focal-plane shutter. Some cameras using stacked sensors, like the Nikon Z 9
The Nikon Z 9 is a full-frame mirrorless camera produced by Nikon. The camera was announced on October 28, 2021.
The Z 9 has the same 45.7 MP resolution as the Z 7 and Z 7II cameras, but uses a much faster stacked CMOS sensor which improves a ...
, completely removed the mechanical shutter. Dynamic range and noise performance are not compromised, because these sensors do not utilize a global shutter.
Shutter lag
Shutter lag is the time between the shutter release being pressed and the exposure starting. While this delay was insignificant on most film and some digital cameras, many digital cameras have significant delay, which can be a problem with fast-moving subjects as in sports and other action photography. Release lag of a bridge camera
Bridge cameras are cameras that fill the niche between relatively simple point-and-shoot cameras and interchangeable-lens cameras such as mirrorless cameras and single-lens reflex cameras (SLRs). They are often comparable in size and weight ...
such as the 2010 Pentax X90 is a relatively short 1/50 s, or 21 milliseconds (ms). The Canon 50d dSLR is specified at 131 ms lag.
In many cases autofocus
An autofocus (or AF) optical system uses a sensor, a control system and a motor to focus on an automatically or manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system ...
(AF) lag is the root cause of shutter lag. Lower-cost cameras and low-light or low-contrast situations will make the effect more pronounced and it is in these cases that AF lag is more noticed. Most AF systems use contrast to determine focus; in situations where contrast is low, the speed at which the camera can determine the best focus can be quite noticeable. Since most modern cameras will not activate the shutter until autofocus is complete, the result is shutter lag. In these cases, the photographer can switch to manual focus to avoid the delay that is attributable to the AF function.
Shutter cycle
A shutter cycle is the process of the shutter opening, closing, and resetting to where it is ready to open again. The life-expectancy of a mechanical shutter is often expressed as a number of shutter cycles.
Projector shutter
In movie projection, the shutter admits light from the lamphouse to illuminate the film across to the projection screen. To avoid brightness flicker, a double-bladed rotary disc shutter admits light two times per frame of film in 24 fps projection, resulting in 24 * 2 = 48 Hz, which is the lower brightness flicker fusion threshold. For 16fps (most silent films and Regular 8mm) and 18fps (Super 8
Super 8 or Super Eight may refer to:
Film
* Super 8 film, a motion picture film format released in 1965
* Super 8 film camera, a motion picture camera used to film Super 8mm motion picture format
* ''Super 8'' (2011 film), a science-fiction fi ...
), a triple-bladed shutter is used instead, as 16 * 3 = 48 Hz and 18 * 3 = 54 Hz.
Shutters are also used simply to regulate pulses of light, with no film being used, as in a signal lamp
Signal lamp training during World War II
A signal lamp (sometimes called an Aldis lamp or a Morse lamp) is a semaphore system using a visual signaling device for optical communication, typically using Morse code. The idea of flashing dots and ...
.
See also
*Photographic lens
A camera lens (also known as photographic lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capab ...
*Kerr cell shutter
A Kerr cell shutter is a type of photographic shutter used for very fast shutter speeds down to nanosecond level.
The Kerr Cell consists of a transparent container (A) filled with nitrobenzene (B) with attached electrodes (C and D). A high voltag ...
*Active shutter 3D system
An active shutter 3D system (a.k.a. alternate frame sequencing, alternate image, AI, alternating field, field sequential or eclipse method) is a technique of displaying stereoscopic 3D images. It works by only presenting the image intended for t ...
References
Weblinks
*
{{Photography