Photographic shutter

The sensitivity of the plates for daguerotype was very low, requiring long exposures measured in minutes. Later wet collodion process allowed reducing the exposure to a few seconds, but its duration still did not require any adjustments, except for the photographer’s watch ^[2] . The role of the shutter was performed by the lens cap ^[3] . With the advent of a highly sensitive gelatin-silver photoprocessing, the required shutter speeds were reduced to tenths, hundredths, and even thousandths of a second, making it possible to record fast moving objects ^[4] . It is impossible to measure such exposures manually, therefore an accurate automatic mechanism was required for their realization. The first photo shutter in history was designed in 1845 by French physicists Fizeau and Foucault for photographing the Sun ^[5] . Such a bright object required even an exposure of 1/60 of a second for shooting a daguerreotype ^[6]

However, the massive use of photo shutter began later, in the early 1880s . In the first cameras with direct sighting, the shutters were considered an accessory, and not part of the design of the camera, and therefore were made removable, most often putting on the lens in front. Later, the central shutters began to perform in a single unit with an iris diaphragm and lens mount . Automatic “instant” shutter speed was often the only one, and besides it, the shutter could only work manually. Switching modes of the shutter consisted in the choice of instant or manual exposure. In later designs, it was possible to adjust the instant exposure using a pneumatic mechanism, first patented in 1886 by Arthur Newman ^[5] . At the beginning of the 20th century , mechanical anchor retarders became common. Modern shutters work out a wide range of shutter speeds, and manual exposure is auxiliary, and is used only in professional photography. The most rapid development of the design of photo shutters was obtained after the First World War, simultaneously with the development of aerial photography technology ^[7] .

The shutter is an essential element of all film and digital cameras. In the latter, the shutter is used to eliminate artifacts peculiar to CMOS matrices most common in phototechnics due to row -by -line reading of data. Some mirrorless cameras support this method of testing exposure, which does not require a mechanical shutter. In 2014, Sony ^[8] , and in 2016, Panasonic ^{[9] [10]} and Canon announced the release of CMOS matrices with simultaneous reading of the entire image using the so-called “global shutter”. These sensors are able to work out the exposure without blocking the light flux by any devices ^[11] . Until recently, only CCD arrays , which were used in phototechnics limitedly due to a number of disadvantages, had similar properties. The absence of the shutter will dramatically increase the resource of cameras and get images of fast-moving objects, devoid of any distortion ^[12] .

With the exception of electronic shutters photomatrix  in which there are no mechanisms, all other types of valves consist of a drive and dampers (shutters), blocking the light ^[1] . The actuators are divided into mechanical and electromechanical . In the first exposures, they are processed by adjusting the width of the gap between the curtains and the speed of their movement by the delaying mechanisms — anchor , pneumatic, or other.

An electromechanical gate requires a power source for operation, without which only one (less often two) shutter speeds are worked ^{[* 1]} . The rest of the exposure range is realized by adjusting the duration of the second shutter holding by an electromagnet . Cheap electromechanical camera shutters of the initial level (for example, Nikon FE10 ) without batteries are generally inoperative ^[13] . In other words, a fully-equipped electromechanical shutter can work only with the presence of batteries, while the mechanical one depends only on the energy of the springs accumulated during arming. There are only a few cameras equipped with hybrid shutters that work in full or partial exposure range with or without batteries: “ Canon New F-1 ”, “ Pentax LX ” and “ Nikon FM3A ”. At the same time, the accuracy of electromechanical valves is significantly higher than the spring ^{[* 2]} . In digital cameras , only electromechanical gates are installed, since their non-volatility in this type of equipment, which is inoperative without power supply, has no practical significance.

Different types of shutters differ mainly in the design and arrangement of the shutters blocking the luminous flux. The shutters can be located near the aperture or focal planes , and on this basis, the closures are divided into aperture and focal . There are cameras (for example, " Bronica ", " Mamiya 645D ", " Hasselblad 2000FC"), equipped with two valves of both types ^{[15] [16]} . Such a device, characteristic of press chambers and medium format mirror equipment, allows you to choose the most appropriate type of shutter, depending on the shooting situation ^[17] . At the same time, both shutters cannot work simultaneously: when the focal aperture is switched on, it is fixed in the open position. Turning on the aperture shutter switches the focal to the light curtain mode. There are interchangeable lenses with a central shutter, designed for cameras with a regular focal lens, for example, the “Leitz Summicron 2.0 / 50” for shooting with a flash-fill device using the Leica devices. In this case, coordination with the main focal shutter, which is in manual shutter mode , takes place with the help of a special attachment mechanism.

This type of shutter is located between the objective lens in a plane near the aperture stop , which is why it got its name. A feature of such shutters is the simultaneous and uniform exposure of the entire frame area, independent of the accuracy of the mechanism setting. Distortions in the shape of fast-moving objects are also excluded. This group can also be conditionally attributed to zalinzovye valves located near the rear lens of the lens, and having similar designs. In the early large-format cameras of the 19th century, front-facing shutters located directly in front of the lens were encountered. According to their characteristics, they were close to zalinzovymi, and were easily installed on almost any camera of those years, performing the role of an additional accessory. In modern equipment, the presence of the shutter is mandatory and its removable design has lost practical meaning. Due to the design features, most aperture shutters are built into the lens mount , and in a large format are not considered a camera accessory. There are several largest manufacturers of manufacturers specializing in the production of central closures, and the most popular types that created them, such as “ Compur ” and “Prontor” ^[3] .

Advantages of aperture locks :

• The simplicity of design and compactness, allowing the use of an aperture shutter in the equipment of any format;
• Great resource at low cost;
• The uniformity of exposure of the entire area of ​​the frame (to a lesser extent characteristic of the lightning closures ^[18] );
• No distortion of fast moving objects, since the entire frame is exhibited simultaneously;
• Noise and vibration during the operation of the shutter are practically absent, due to the small mass of moving parts;
• The ability to simplify the selection of shooting parameters using the scale of exposure numbers ^[19] ;

Disadvantages of aperture valves :

• Disadvantage of use with interchangeable optics;

According to the principle of action, aperture valves can be divided into slotted, central and louver ^[20] . Slit aperture shutters are often called obturator . The most famous example of a slit aperture shutter is a butterfly valve, which consists of a metal sector with an aperture rotating on an axis, which is actuated by a spring connected with a release lever.

Valves of this type are distinguished by the smallest number of parts, which determines the low cost, increased reliability and low requirements for manufacturing accuracy. However, significant drawbacks are cumbersome (the radius of the disc is much larger than the overlapping hole) and the difficulty of adjusting shutter speeds can be used mainly in entry-level cameras and in specialized devices, such as aerial cameras .

Central shutter

The central shutter is a kind of aperture shutter, the shutters of which, when activated, open the lens hole from the center to its edges and close in the reverse order ^[21] . Such shutters, as a rule, are installed between the objective lens or directly behind the rear lens. Central closures are divided into direct action (rotary) and return action (reversible) ^[20] . The first type, due to its bulkiness, became widespread only in special photographic equipment, for example, in aerial cameras. In general purpose photographic equipment, only central return valves are used.

The mechanism of such a shutter consists of several turning metal petals fixed on the axes along the edges of the round frame. The reciprocating rotational motion of the petals opening and closing the hole is carried out by a system of springs and levers ^[22] . When exposed, the petals open the active lens opening symmetrically from the center to the edges and close in the opposite direction ^[23] . As a result, the light falls simultaneously on the entire surface of the photosensitive element. The action of the petals of the central shutter is like an iris diaphragm: as they open, the illumination of the entire area of ​​the photosensitive element increases evenly, and when it closes, it decreases to zero ^[24] . The use of a central shutter is typical for large-format cameras and inexpensive amateur cameras with a non-replaceable lens. In addition, the central shutter is regularly used in almost all dual-lens reflex cameras . Interchangeable lenses for some single-lens reflex cameras are also equipped with center shutters, often within the entire optical range ^[25] . In modern digital equipment such shutters are installed in compact and pseudo-mirror cameras .

Disadvantages of central return valves :

• The dependence of the speed of the maximum light diameter, limiting the limit aperture lenses;
• The fundamental limitation of speed, which does not allow to obtain shutter speeds shorter than 1/500 second ^[26] ;
• Low efficiency (light output);

In the rotary central shutters, the petals perform not a return, but a continuous rotational movement, which allows to obtain very high efficiency and short exposures. However, the design of such closures (for example, “Rapidin” or Soviet “ZBS”) is much more complicated than that of return valves, which predetermined their narrow specialization ^[27] . The magnitude of the shutter speed during the return movement of the petals can be reduced only in the diaphragm gates with small relative apertures.

The shutter-diaphragm , diaphragm shutter - the central shutter, the maximum degree of disclosure of the petals of which is regulated, due to which it simultaneously performs the role of the diaphragm . Because of the design features of the combination “shutter speed - aperture” in cameras with such a shutter, as a rule, they are fixed. Both parameters are tightly coupled: for example, the relative aperture f / 2.8 is achievable only at 1/60 shutter speed, and the f / 16 aperture is only at 1/250. The shutter-diaphragm is widely used in small-format cameras with the simplest exposure automatic , designed primarily for novice amateur photographers ( LOMO Compact-Avtomat , Elikon-35S , FED-35 , Argus C-3 , etc.) ^{[ 28]} , as well as in inexpensive models without an exposure meter, such as Agat-18 , Elikon-535 . Due to the shorter stroke of the petals, the minimum shutter speed-aperture (for example, in the Soviet " FED-Micron ") can be shorter than the usual central shutter and reach 1/800 seconds with minimal relative apertures . The efficiency of the central shutter does not exceed 80% ^[29]

Shutter type shutter

The shutters of this variety are placed between the lenses of the lens and are used extremely rarely, since they require sufficient space inside the lens ^[30] . They became widespread in automatic photo printers and cameras for special types of surveys ^[1] . In aerial cameras, a shutter-type shutter is used with high-aperture optics ^[31] .

Light is overlapped by a set of narrow lamella plates that simultaneously rotate around the axes. When the shutter is open, the plates are directed along the optical axis , passing light. To close the shutter, it is enough to turn the plates 90 °. Due to the small mass of each individual plate, the inertia of the shutter is small and the drive mechanism is simple. The efficiency of the shutters-shutters is close to the efficiency of the central shut-off valves and does not exceed 0.6, since the full opening phase is absent ^[32] .

The focal shutter, as the name implies, is located near the focal plane , that is, directly in front of the photosensitive material ^[33] . For this reason, the design and dimensions of the valves of this type determine the device of the entire camera, in contrast to aperture, which are made as a separate unit or embedded in the lens mount .

Advantages of the focal shutter :

• The possibility of working out very short exposures inaccessible to the aperture valves;
• Ease of use in equipment with interchangeable optics ^[34] ;
• The absence of any restrictions on the maximum aperture of lenses ^{[* 3]} ;
• High efficiency (high luminous efficiency) ^[35] ;

Disadvantages of the focal shutter :

• The risk of uneven exposure of the frame with inaccurate adjustment ^[18] ;
• The impossibility of shooting with electronic flash on short exposures ^{[* 4]} ;
• Distortion of the form of fast moving objects ( temporal parallax );
• Increased noise and vibration due to the relatively large mass and size of moving parts;
• The risk of burning the sun in the case of cloth blinds;
• The direct dependence of the dimensions of the mechanism on the frame size and the inconvenience of use in large - format equipment;

In most curtain-slotted shutters, the curtains move in front of the personnel window at a constant speed, and the shutter speed is controlled by the width of the gap between them. The first and second shutter curtains move independently of each other under the action of springs, adjusted in such a way that the shutter speeds coincide ^[36] . A gap of variable width is formed by a mechanism that sets the moment of release of the lock of the second curtain. Before starting the next shot, the shutter cocks again and the curtains return to their original positions without a gap ^[37] . The efficiency of the shutter curtain reaches 95% ^[29] , and the minimum shutter speed can reach 1/16000 s (“ Canon EOS-1D ”, “ Nikon D1 ”) ^[38] .

The shutter can be both vertical and horizontal with the stroke of the exposure slit. Horizontal stroke, as a rule, have Leica closures with elastic curtains, wound on drums. Vertical movement found in such valves is rare and more typical of lamellae, which have become widespread in modern equipment. Each shutter of such a shutter consists of several (usually 3-4) rigid metal lamellae moving on a hinged-lever drive parallel to the focal plane. When opening, the lamellae fold into a narrow stack, and when closed, they fold out, forming a wide curtain.

For photography with a photo flash, most modern shutters are equipped with a sync contact triggering the discharge ^[29] . The simplest sync-contact is two electrical contacts in the circuit of an electron flash condenser, closing up by the shutter mechanism at the moment of its full opening. Such a sync contact is denoted by the Latin letter "X" ^[39] . Regardless of the type of shutter, the most optimal moment of the flash is its full opening. However, the aperture shutter is most convenient for shooting with a flash, since it exposes the entire area of ​​the frame simultaneously. This allows you to use the flash at any shutter speeds. Focal closures can be synchronized only at relatively long shutter speeds, providing the moment of full opening of the frame window.

First / second curtain sync

The duration of an electron flash pulse is significantly less than the shutter speed (1–5 milliseconds against hundredths of a second). It is not of great importance for fixed objects in the case when the exposure obtained from continuous illumination is significantly less than the exposure obtained from flash light. However, if the subject moves fast and both exposures are comparable, continuous illumination gives a blurry image that folds sharply from pulsed light. When synchronizing with the first curtain, the flash fires immediately after the shutter opens, after which the object has time to move forward in the course of its movement until the second curtain closes.

The result is a blurred image of the object formed by continuous illumination, located in front of the sharp image obtained from the flash. Thus, the movement in the photo visually looks in the opposite direction. This effect can be avoided by the second-curtain sync, when the flash fires just before the frame window closes. In this case, the image of the object is first exposed to continuous illumination, and only then it is illuminated with a flash, ensuring normal visual perception of movement in the image.

To do this, most modern electromechanical valves are supplied not with one, but with two synchronous contacts: one of them works after the first shutter is fully opened, and the other at the moment of giving the command to close the second. The choice of the desired sync-contact occurs through the camera or flash menu, corresponding to the switching type of synchronization. The disadvantage of the second-curtain sync is the unpredictability of the flash firing moment, which is especially apparent at long exposures.

Until the end of the 20th century, electronic closures were called electromechanical shutters ^{[40] [18]} . With the proliferation of digital photography, an electronic device for extracting exposures based on adjusting the readout time from the matrix without any mechanisms blocking the light began to be called electronic. Exposure is determined by the time between zeroing the matrix and the moment of reading information from it. The use of an electronic shutter allows shorter shutter speeds (including flash sync speeds) to be achieved without the use of expensive high-speed mechanical shutters. In addition, the absence of inertial mechanisms allows for serial shooting with high frequency. Some cameras allow you to choose between a mechanical and an electronic shutter for high-speed shooting.

The advantages of the electronic shutter include the absence of moving parts, creating noise and vibration. The electronic shutter works silently and does not reduce the sharpness of images due to shaking. Among the shortcomings of the electronic shutter, one can identify the distortion of the image caused by its line-by-line reading (“ rolling shutter ”), as well as the increased likelihood of blooming (for example, when it hits the sun).

In addition, SIMD matrices are available that have an individual electronic shutter in each pixel . In this variant, the optimal exposure time is adjusted for each pixel depending on the level of illumination in this area of ​​the frame ^[41] . As an electronic shutter, instantaneous light modulators based on the Pockels effect can be used.

• Obturator (optics)
• Rolling shutter
• Slit photo

• A. Volgin. We shoot for a wide format (rus.) // " Science and Life ": magazine. - 1999. - № 11 . - p . 74-80 . - ISSN 0028-1263 .

• Alexander Ditlov. The invention of the curtain-slotted shutter (rus.) // " Photography ": the magazine. - 1994. - № 1 . - p . 41 . - ISSN 0371-4284 .

• E. A. Iofis . Photo kinotekhnika / I. Yu. Shebalin. - M.,: “Soviet Encyclopedia”, 1981. - pp. 54-56. - 447 s.

• N. P. Lavrov, A. F. Stetsenko. Aerial photography. Aerial photography equipment / N. T. Kuprina. - M .: "Nedra", 1981. - 296 p.

• Vladimir Levashov. Lectures on the history of photography. - 2nd ed .. - M .: " Liters ", 2014. - ISBN 978-5-903788-63-7 .

• N. D. Panfilov, A. A. Fomin. Quick reference amateur photographer. - M.,: "Art", 1985. - p. 46-55. - 367 s.

• Vladimir Samarin. System DSLRs: a squad of unmanned (rus.) // "Photoshop": magazine. - 2001. - № 12 . - pp . 14-23 . - ISSN 1029-609-3 .

• E. D. Tamitsky, V. A. Gorbatov. The educational book on photography / Fomin A.V., Fivensky Yu. I. .. - M .: “Light Industry”, 1976. - P. 46-51. - 320 s. - 130 000 copies

• M. Tomilin. Evolution of photo shutters (rus.) // Soviet Photo : magazine. - 1977. - № 3 . - p . 39-41 . - ISSN 0371-4284 . Archived December 10, 2015.

• Elena Fisenko. Tropic Nettel (rus.) // Photoshop: magazine. - 2000. - № 7-8 . - p . 160-167 . - ISSN 1029-609-3 .

• Fomin A.V. § 5. Basic units and mechanisms of cameras // General Photography Course / T.P. Buldakova. - 3rd. - M.,: “Legprombytizdat”, 1987. - p. 27-32. - 256 s. - 50 000 copies

• Michel Frizo New history of photography = Nouvelle Histoire de la Photographie / A.G. Heirs, A.V. Shestakov. - SPb. : Machina, 2008. - pp. 233–242. - 337 s. - ISBN 978-5-90141-066-0 .

• Andrey Sheklein. Ottomar Anschyutts, or at the cradle of the curtain shutter (rus.) // Photoshop: magazine. - 2002. - № 10 . - p . 50-54 . - ISSN 1029-609-3 .

• M. Ya. Shulman. Cameras / T. G. Filatova. - L.,: “Mechanical Engineering”, 1984. - 142 p.

• Dan Havlik. Superfast video recording of the curtain shutter operation of a modern DSLR (English) . DSLR News . Shutterbug magazine (January 29, 2015). The appeal date is January 30, 2015.

• Peter Angarsky. PHOTO HISTORY IN RUSSIA (rus.) . Photo Club ID "Connect". The appeal date is January 30, 2015.