Shutters

Until the end of the wet-plate period exposure was generally controlled by the lens-cap, the main exception to this being stereo cameras that were often fitted with a shutter ensuring both images received the same exposure. From the gelatine dry-plate period plates became more sensitive and exposure times decreased, a shutter then became a necessity. At first shutters were in the form of attachments to be fitted to the camera by the photographer later they became an integral part of the camera.

Shutter Types

Early Pivoted

This type was included on many early landscape lenses from the earliest times through to the late 1860s. They consist of a simple, manually operated, pivoted plate at the front of the lens. An interesting variation is found on some Ross lenses where the plate is inside the lens and operated by a short lever on the outside of the barrel.

Flap

These consist of one or two hinged flaps usually placed in front of the lens but also found on the inside of studio cameras. In their simplest form one, manually operated, flap is deployed, more elaborate models used a spring or rubber band as power with variable tension or pneumatic delay. The two flap version, where one flap uncovered the lens and the other covered it, provided higher speeds and more even exposure.

Simple flap shutters are often found on early cameras (1860s) especially stereo. They were also popular on studio cameras from the 1880s where their silent action was an advantage.

Examples of double flap shutters are found on Thomas Skaife's camera of around 1858; Furnell's of 1885 and the Guerry.¹ The Cadett single-flap pneumatic shutter of 1878 was operated by pushing air into a rubber bulb to which the flap was connected.²

Flap shutters were sometimes combined with a drop shutter, so that the flap was operated to start the exposure and a plate would drop to end the exposure. The firm of Reynolds & Branson specialised in this type of shutter patenting and producing many kinds with increasingly sophisticated mechanisms.³

A curious idea, that might be described as a venetian-blind, was proposed in 1888. A number of laths ran across the lens and could be rotated to an open or closed position. The same arrangement was resurrected many years later on an aircraft camera.⁴

Rotating

Rotary / Sector

In various forms these shutters consist of a pivoted plate containing an aperture rotating across the lens opening or near the focal-plane. Most fall into one of two types:

• The shutter plate has to be returned to its original position after the exposure, a secondary plate may be present to cap the aperture.
• The shutter can be re-tensioned following the exposure and pass across the lens in the opposite direction. A popular arrangement on simple cameras was for the spring powering the shutter to re-tension itself when the shutter is released, an arrangement used on the 1896 Pocket Kodak.⁵

A spring or rubber-band usually provided the power; tension or, on better models, pneumatic delay was used to control the exposure. The aperture may be shaped to give more exposure to the foreground and, by using a second plate, be adjustable in size to control the exposure.

Early examples are by Chadwick, 1880, which was suitable for use on stereo cameras. A popular model was the elastic band powered model of 1885 from Lancaster. Many Shew strut cameras are fitted with a rotary shutter brought out in 1885. The Beck Frena used a rotary shutter with a secondary plate to change the size of the aperture. The popular Sibyl had a sector shutter where the aperture was extended so forming a V shape, it was tensioned in either position and passed in alternate directions between the lens elements. Liesk's Patent Sky shutter, sold by Marion, had an aperture shaped to give extra exposure to the foreground and was fitted with Cadett's pneumatic release. The Eastman Sector shutter fitted to the Folding Kodak of 1889 had a separate capping blade when the shutter was re-set.⁶

Two sectors moving in opposite directions are sometimes employed, one of the earliest was by C.J. Wollaston in 1885. Several versions were produced, they were spring powered with a friction pad to regulate the exposure. Another was the Bain sold by Marion around 1889.⁷

Cylindrical

A cylinder, rotating on an axis at 90 degrees to the axis of the lens, contains a hole through which the exposure is made. Most famously found on the 1888 Kodak.

Hemispheric

Somewhat similar to the cylindrical shutter but here the shutter plate consists of part of a sphere that rotates behind the lens, found on the Photosphere and a few other cameras.

Guillotine

A plate or plates slide across the lens opening, each in a single direction.

Single Guillotine

Consists of a plate with an aperture which moves across the lens opening. A second plate may be present to provide self-capping.

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 simply gravity. Later they were fitted to run horizontally in hand cameras where they were spring powered with spring tension or pneumatic regulation.

Double Guillotine

Two plates moving in the same direction with a delay before the second covers the opening made by the first. The delay may be variable to control the exposure.

In some versions both plates have apertures and overlap to produce variable exposure and self-capping on others there are no apertures, the first plate uncovers the lens the second then covers it. G.L. Addenbrooke developed a shutter with a clockwork timer to release the second blade.⁸

Double Guillotine

Two plates move in opposite directions across the lens opening.

The common arrangement was for each plate to have an aperture and so produce an opening from the centre of the lens as the two plates passed each other. An early model was the Sands' Patent of 1881. W. Heath proposed a shutter where the openings in the horizontally moving plates were wider at their base to give extra exposure to the foreground. Lancaster sold a very popular model from 1889.⁹

Two plates without apertures were proposed by Thomas Forrest, sold as the Due-ratio, the plates were connected by cords, as one was raised to uncover the lens the other started its descent to cover the lens, this gave extra exposure to the foreground.¹⁰

Return

Consists of one or two plates that move away from the lens opening and then return.

Single Blade Rectilinear Movement

A simple and popular design was known as the 'Rebound', a blade was held in front of the lens by a catch against the force of an elastic band, when the catch is released the elastic band pulls the blade up and is dislodged allowing the blade to fall back and cover the lens. Examples are by Cubley & Preston and J.T. Daniels.¹¹

From the late 1880s this movements was used on some sophisticated shutters offering a full range of speeds. They gave more exposure to the foreground and, in some cases, could be fitted into the diaphragm slot. Examples are: W.L. Sarjeant's; Optimus Plunge from Perken, Son & Rayment; A.S. Newman's which incorporated a pneumatic time valve; the Evolute from Gotz; G.S. Grimstone introduced several similar designs.¹²

Two Blade Rectilinear Movement

These have the advantage over the single blade type that the lens is uncovered from the centre.

J. Swift patented an arrangement where the lower blade was pulled down by a spring, the upper blade was pulled up by a spring that dislodged itself (similar to a rubber-band drop shutter) allowing the upper blade to fall and cover the lens. A time setting and pneumatic release were fitted. Dallmeyer and Beauchamp patented a model where the blades operated horizontally.¹³

Pivoted Single Blade

Essentially an 'Early Pivoted' shutter but with a spring or rubber-band to return the blade. An early example was the Watson Snap shutter of the early 1880s.¹⁴

Pivoted Two Blade

An extremely popular form typified by American shutters of the late 1890s. Spring powered with tension or pneumatic control.

Early designs were by Spurge and Whitcher, the patents for which also covered two blades working rectilinearly, and Greenhall's of 1889.¹⁵

In the late 1890s these shutters started to be built into small units along with a diaphragm and lens for fitting to hand cameras. Examples are from Kodak, Bausch & Lomb and Wollensak.¹⁶

Pivoted Two Blade - separated pivot points

In this arrangement the blades are separately pivoted from points each side of the lens. This type of shutter was used on early models of the Adams Yale detective camera.

Diaphragm

Reciprocating

Essentially an elaboration of the 'pivoted two blade return' shutter with more blades. They were spring powered with exposure regulation by tension, pneumatic delay, friction or gear train. The reciprocating form proved to be by far the more popular of the two types of shutter, precision construction and thin, balanced, blades allowed the shutter to open and close quickly relative to the overall exposure time. Each of the blades has a pivot point, generally, they are moved by a stud on the blade working in a slot in a ring, rotating the ring moves the studs and opens the blades (or the reverse i.e. the stud is on the ring and the slot is in the blade). Some designs had the stud/slot operate only a single blade and had all the blades connected to each other by similar a slot/stud arrangement.

Early designs were by T.R. Dallmeyer and F. Beauchamp, in a series of patents from 1887. One version had 6 leaves and also acted as a diaphragm by limiting the degree of opening of the blades. The Bausch & Lomb design of 1888 had the blades connected to each other, later modifications used the conventional arrangement. Voigtländer and Goerz also produced designs in the 1890s. The important introduction of a gear train to regulate the exposure was on the Ilex shutter by Brueck and Klein. This same arrangement was licensed by Deckel and included in their Compur shutters of 1912.¹⁷

Rotating

In this form each blade rotates in one direction only. The blade consists of most of a circle with a section removed. High speeds were possible as there was no reversal of motion. Dietz patented a design with four blades that was sold in Britain by Ross as the Multispeed.¹⁸

Mattioli patented a design that might by described as three small pivoted sectors each with an aperture able to move across the lens opening, the shutter was sold by Shew.¹⁹

Roller-Blind

These consist of a blind or blinds wound on rollers which, operating close to the lens, form an aperture. The usual arrangement is a single blind with an aperture, the exposure time being controlled by the tension of a spring. More elaborate forms have a secondary blind for self-capping. Other designs have two blinds connected by tapes allowing the aperture width to be varied. Spring powered with exposure variation by tension, slit width or pneumatic delay.

Although a few designs date from the wet-plate period this type of shutter became popular from the late 1880s. An early model was from J. Kershaw, patented in 1885.²⁰ J. E Thornton patented his well-known shutter in 1886, it was manufactured from 1887 and proved to be the start of a long line of shutters with many different models that were to remain on sale until the start of the second world war. A self-capping model with a safety blind was introduced in 1891 and a model for the studio having two blinds moving in opposite direction and opening from the centre was produced in 1894.²¹

Slow speeds were difficult to attain simply by using spring tension, Arthur Newman introduced a shutter with a pneumatic delay cylinder giving a range of speeds from 1 second to 1/50.²² Thornton Pickard solved the problem by a simple air valve that fitted in the bulb release tube.

A very elaborate mechanism was included in the Ensign shutter of around 1911, on this model the slit width was variable with the lower blind linked by friction to the tapes of the upper blind.²³

Focal-Plane (Roller-blind)

Generally, 'Focal-Plane' refers to a blind or blinds wound on rollers operating near to the focal plane, the gap in or between the blinds forming the exposing aperture. The power is provided by a spring inside the roller. The exposure is varied by adjusting the spring tension or the aperture width. For slow speeds a pneumatic or mechanical delay may be used. A 'focusing position' is often included consisting of an aperture the full size of the image, it is sometimes set by winding the blind past the regular exposure setting.

Where both tension and aperture can be changed a table was usually attached to the camera so that the exposure could be found.

With the above definition in mind the first commercially produced camera with a focal-plane shutter would seem to be the Loman Reflex of 1889, the idea was published earlier in 1882 by B.J. Edwards and included in his patented camera of 1889 but not commercially produced, the Anschütz appeared in 1890 though patented in 1888.²⁴

The more common blind arrangements are shown below.

Single Blind

The simplest form of shutter has a single blind with a fixed aperture, the exposure was varied by adjusting the tension. The Loman Reflex was of this type.

An improvement was for the blind to have multiple apertures of different sizes each selectable when setting the shutter. Although simple in form the multiple aperture type was used on cameras such as the Graflex. Not self-capping.²⁵

Two Half-Blinds

A more flexible arrangement was to split the single blind in two and connect them in some way to provide a variable aperture.

Two Half-Blinds - linked by a sliding cord

By having two blinds connected by a cord the aperture could be made variable. A popular model had a cord stretched between the two blinds, on one blind the cord was attached to a plate that could be moved along the edge of the blind and so adjust the width of the aperture. The exposure setting was marked on the blind.

This type of shutter has the disadvantage that the back of the camera has to be opened to access the sliding plate. It was used on the first folding Goerz Anschütz camera of 1896 and in a slightly different form on the earlier box shaped camera of c. 1892. It continued to be used, but mostly on cheaper models. Not self-capping.²⁶ On some models, at least, of the Spiegel Reflex by Dr. Hesekiel the slider is adjusted on both the upper and lower blinds. The ends of the cord fit into one of a series of notches on the edges of the blind.

An arrangement was used on Thornton-Pickard shutters from 1893 where the two blinds were joined by chains. To change the aperture the chains could be unclipped and positioned with a different number of links in place. The chains were spring-loaded, excess links being pulled into tubes mounted on the edges of the blinds. The nominal speed, as set by the tension, multiplied by the number of links gave the speed.²⁷

Two Half-Blinds - linked by tapes

The disadvantage of adjusting the aperture on the blinds themselves was overcome by linking the blinds by tapes or cords which could be adjusted from outside the camera. Tapes were attached to the lower edge of the top blind, looped around a fixing on the top of the lower blind and then fixed to drums at the top of the camera. The drums could be on the same shaft as the upper blind roller, both would move together when setting the shutter but the tape drums could be rotated separately to adjust the length of tape. Not self-capping.

This arrangement, though having the blinds linked by cords rather than tape, was patented by Anschütz (1890). Used on the Kershaw shutter of 1904.²⁸

Two Half-Blinds - linked by friction

The upper blind has extended tapes attached to a roller at the bottom of the camera. The lower blind is wound on a second roller and attached to the tapes of the upper blind by a friction grip.²⁹

When setting the shutter both blinds are pulled up by turning the upper roller, when the friction grip reaches the top it stops, the upper blind can be wound further which pulls varying lengths of tape through the friction grip to set the required aperture. At the end of the exposure the friction grip reaches the bottom of the camera, the spring acting on the top blind is able to pull the tape through the friction grip and so close the aperture making the shutter self-capping. Used on several Ensign cameras.³⁰

Two Independent Blinds

Rather than have a single blind with a variable aperture, with this type of shutter, two complete blinds are used with the aperture formed by their relative positions.

Two Independent Blinds - variable tape length

The upper blind is connected to a lower roller by tapes, the lower blind is wound on a roller at the bottom of the camera and connected to an upper roller by tapes. The length of tape (attached to either blind) can be adjusted to vary the exposure. Mostly self-capping.

This arrangement was shown in a patent by A.L. Adams. The adjustable tape (attached to the lower blind) passed through the lower edge of the upper blind and is wound inside the upper-blind roller. The shutter speed was written on the tape and could be seen through a viewing port in the roller when aligned to a yellow window in the top of the camera. The blind arrangement was also patented by Newman where only one lower roller was used.³¹

Two Independent Blinds - variable tape length

In another form, the upper blind contains an aperture of fixed size (the size of the image), the lower blind is wound on a lower roller and connected by tapes to drums on the upper roller. The length of tape, and so the exposure, can be adjusted by winding the tapes on the drums. Both blinds are wound by turning the upper roller, the drums are able to slip on the roller. Used on the Newman & Guardia Folding Reflex where it was self-capping.³²

Two Independent Blinds - blind displacement

Arthur Newman used two blinds each with a fixed aperture, the exposure was varied by displacing one blind relative to the other by winding the blinds to different extents. This arrangement was used on the Self-Focusing Reflex and Square Reflector cameras.³³

Time Delayed Second Blind

An important development was to use the same two-blind layout but to release the blinds at different times to produce a variable aperture. The second blind was released by the travel of the first blind.

Though similar to the previous shutter descriptions in blind arrangement, on this shutter the tape lengths are fixed. First used on the Adams Minex of 1909 and later on the Leica. Self-capping.³⁴

A patent by H.R. Cook in 1893 preceded the Minex but was not commercially produced, it is described below.

Focal-Plane (Other types)

William England's guillotine

William England used a simple guillotine shutter with variable slit width mounted within the dark-slide. This is often referred to as the first focal-plane shutter.³⁵

Alexander Cowan developed a wooden two blade guillotine shutter that fitted to the back of the camera. The blades started on the same side of the camera and moved in opposite diagonal directions. Not commercially produced.³⁶

Pleated blinds - Anschütz

Pleated or corrugated blinds were used in the 1891 Anschütz camera. The patent shows two blinds with an elaborate screw mechanism to vary the aperture, a coiled spring pulled the blinds down.

Pleated blinds - Cook

Pleated blinds were also proposed by H.R. Cook in 1893. In his design there are two blinds, one was attached to the top of the camera and pulled down by a cord wound on a spring roller, the lower blind was attached to the bottom of the camera and was also pulled down by a spring roller. Two cords passed from each end of the lower blind out of the camera casing, pulling these raised the lower blind which would meet the upper blind and both would rise in contact to the top of the camera where they locked into two triggers, in this way they were self-capping. One of the cords was wrapped around a wheel on the camera top, as the cord was pulled this rotated until it came to a stop against the release trigger for the lower blind. When the release was pressed the lower blind would descend and the wheel rotate, at a certain point in its rotation an arm on the wheel would trigger the release of the upper blind, the position of the arm could be altered to vary the exposure.³⁷

The idea of a time delay between the release of the blinds is probably a consequence of using pleated blinds that have a linear movement. Interestingly the patent also mentions that the same mechanism could be applied to blinds wound on rollers.

Eastman/Cossitt

In this early roll-film camera the shutter consisted of a wedge-shaped enclosure with a large opening near the lens and a narrow slot near the film, the enclosure is able to pivot on a horizontal axis to expose the film. The slot size could be altered, the enclosure fell under gravity probably retarded by a spring.³⁸

Sigriste

The shutter consists of two metal plates with a variable separation between them moving across the focal plane. The plates are connected by a pleated-cloth sleeve to the lens area which cuts off light except to the shutter plates. The separation of the plates is varied by a screw arrangement working on one of the plates. This is set by a lever on the outside of the camera beneath the shutter speed plate. The setting is read against a pointer moving around the speed plate. The tension is provided by a coiled spring and adjusted by an arm on the speed plate. The plates are connected to the shutter spring by cords which wind around a pulley acted on by the spring. The speed plate itself shows the speed for the tension/slit width combination, of which there are many. Operating the magazine sets the shutter which is released by two levers on the magazine.³⁹

Houghton and Edwards

Studio shutters have the special requirements of being silent and not visually distracting; one, developed by George Houghton and W.A. Edwards in 1896, consisted of four fan-like sections the ends of which were connected via links to a pneumatic cylinder. Pushing air into the cylinder moved the links and opened the fans, a spring pulled the fans shut at the end of the exposure. Being situated next to the plate may have caused some problems with dust.⁴⁰

Eyelid

A form used exclusively in studio cameras consisting of two pleated parts in the form of an eyelid.

Mirror/Reflex

In various arrangements the mirror of a single-lens reflex in the down position completely blocks light reaching the focal plane. When the mirror rises it carries with it an attached plate with an aperture to make the exposure or simply pulls up a capping plate, the exposure having stated with the mirror movement. It was a type popular on cheaper reflex cameras of the 1920s and 1930s but there were several designs from the 1890s and, in a simpler form, was used on the first single-lens reflex by Sutton.

Combined Shutter and Iris

Several diaphragm shutters of the 1890s and 1900s allowed the shutter blades to open to a varying extent thereby also functioning as an iris. Examples are B&L Iris, Goerz Sector 1897 and Volute 1902.

The earlier Sands shutter of 1881 was either a shutter working at maximum aperture or a diaphragm working at 'B'. The two blades performing both tasks.

Calibration

As might be expected shutters are normally marked with the shutter speed, some, especially French, are marked with arbitrary numbers. Others are marked with the weather conditions in place of or along side the actual speed, examples are the Autotime setting found on Kodak cameras (introduced in 1909) and Actino Midge by Butcher (1900)⁴¹

In Britain shutters were marked with B - the shutter remained open as long as the release button was held and T - the shutter opened when the release button was pressed and closed when next pressed. In Germany the equivalents were O and Z. I was sometimes used for instantaneous, the equivalent in Germany being M.

Flash Synchronisation

The early way of using flash was to manually open the shutter, fire the flash and close the shutter. An early proposal to synchronise the shutter with a magnesium powder flash was from R. Slingsby, a lever operated a set of bellows that sent a puff of air to the flash lamp and compressed a rubber bulb connected to the shutter. A similar but less elegant device was patented by Hart.⁴² From around the turn of the century several methods were proposed to synchronise the shutter with flash powder devices. One of the earliest was the Guerry of 1901.

External synchronisation units were available from the early 1930s for use with the newly introduced flash bulbs. Few cameras prior to World War II had built-in synchronisation, probably the first was the Exacta B of 1935.

Synchronisation of bulbs with leaf shutters was straightforward, a bulb took around 10 ms to reach half-peak and remained there for around 20 ms, a shutter set at a speed of 1/25 was open for 40ms, so firing the flash then the shutter gave ample time for the flash to be active while the shutter was open. At higher shutter speeds the tolerances were less, requiring dedicated synchronisation units probably built into the camera.

With focal-plane shutters the situation was very different, on a quarter-plate or 4" x 5" camera the blinds might take 30 - 50 ms to travel across the exposure area, this was longer than the duration of normal bulbs. Special, long duration, bulbs were produced for synchronisation at moderately fast speeds. On 35 mm cameras the travel time was less, in the order of 25 ms, and the range of bulbs was larger.

Electronic flash has minimal duration and latency time, on leaf shutter the shutter was fired and then the flash unit, synchronisation at all speeds was possible. On focal-plane shutters the flash was fired when the first blind had uncovered the exposure area and the second blind had not started its travel.

Types of Synchronisation

M

Electrical contact to the flash is made shortly (17 ms) before the shutter is fully open. For class M and S flash bulbs.

F

Similar to M but for bulbs reaching their peak faster, the shutter and flash are fired simultaneously. For MF and M flash bulbs at slow speeds.

FP

This is for slow burning flash bulbs having a long duration. On focal-plane shutters synchronisation can be at high speeds.

X

Primarily for use with electronic flash. With leaf shutters electrical contact is made when the blades are fully open. Used with electronic flash at all speeds or some flash bulbs at low speeds. With focal-plane shutters contact is made when the image area is completely uncovered.

The designation of X, FP etc. was not used until the 1950s. Prior to this the synchroniser, or flashgun was matched for a particular camera and flash bulb.

The standard co-axial (PC) flash connector appeared in the mid 1950s. The 'Hot-shoe' was introduced on the Univex Mercury.

Delayed Action, Slow Speeds and Shutter Release

Delayed Action

Diaphragm shutters with built-in delayed action appeared in the 1920s, as external accessories they were available earlier. Focal-plane cameras with built-in delayed action appeared in the 1930s.

Most mechanisms worked on air escaping from valves or clockwork, there were also several suggestions for using burning fuses in various ways.⁴³

Slow Speeds

Focal-plane and, to a lesser extent, roller-blind shutters could not operate at slow speeds without introducing a separate timing mechanism. A simple and popular accessory was the air valve that could fit in the tube of a bulb release, some cameras simply included one of these within the camera.

Shutter Release

The familiar bulb release was a common way of releasing the shutter, squeezing a rubber bulb pushed air into a small bulb or pneumatic cylinder in the shutter which tripped the mechanism, the name stuck and we still have a B setting on shutters.

Several 'Self-Portrait' shutters were produced fitted with a string that could be pulled by the photographer to trip the shutter.⁴⁴ Wire or antinous releases based on Bowden's patent were introduced in the early 1900s and quickly replaced the rubber bulb and tube. There was no standard for attaching the cable to the camera but the Deckel tapered screw was gradually adopted.⁴⁵

Electro-magnetic releases were proposed from the 1870s but did not prove popular.⁴⁶

Power and Regulation

Power

The shutters shown above use as their motive power spring tension, rubber bands, gravity or in some cases they are simply operated by the finger. The first electro-magnetic shutter was probably by Cussons and Cowan in 1878, it is described as being "opened and closed by an electromagnet". The Muybridge shutter of the same year is sometimes termed an electro-magnetic shutter but it was a two-blade guillotine type powered by springs, only the release was electro-magnetic.⁴⁷

Regulation

The shutter could be held open or at least its speed varied by different means: spring tension, pneumatic delay, friction, mechanical delay (e.g. clockwork or gear train), air resistance (by using vanes) and in modern times electronic circuits.

An interesting and early electronically controlled shutter regulated by a selenium cell to give automatic adjustment of exposure times was patented by Carl Eisner in 1902. The mechanism describes the current flowing through a selenium cell varying the speed of an electric motor which drives a rotary shutter, i.e. the greater the light intensity the faster the shutter will rotate and lessen the exposure time. Attached to the shaft of the motor was a breaking device (a coiled spring acting on a brake disk) used to adapt the shutter to the speed of the lens.⁴⁸

Pneumatic Delay

Pneumatic Delay Cylinders were a common method of regulating exposure. The delay can be whilst the piston moves into or out of the cylinder or, less commonly, alternate so both the in and out stroke are used.

The simplest has a cylinder open at the piston end with a valve to control air flow at the other end. The valve was often a shaped piece of metal working in a small hole in the cylinder. A problem with this arrangement was that only a small movement of the valve covered the entire speed range making calibration and manufacture difficult. Being open also allowed dust to enter the mechanism. Newman's Patent shutter of 1886 is of this type.⁴⁹

Another arrangement was to have a sealed cylinder and to have air flow take place between an attached chamber. As the piston descends air flows out from the bottom of the cylinder and in at the top of the cylinder. A valve connected to the speed indicator would work in one of the holes. The shutter fitted to the N&G Universal has this arrangement.⁵⁰

Rather than have a valve regulate the air flow, the length of the piston stroke could be varied. The speed setting altered the position of the cylinder relative to the piston (or the other way round). The advantages of this method was that there was no valve and therefore the inlet/outlet hole was of fixed size, secondly, a large movement of the cylinder was required to cover the speed range, this arrangement gave more precision in calibrating the speed setting. Newman's, rejected, patent of 1890 shows an open cylinder with the initial position of the piston altered by the speed setting. Hill and Adams' patent of 1892 shows a fixed piston and a moveable cylinder.⁵¹

The moving cylinder could be sealed and combined with a side chamber or air flow could be through a gap in the piston head. This type of delay was used on the Adams de Luxe camera of 1898 and is mentioned in Hill and Adams' patent, BP 12029/1892.

References & Notes

Coe, Cameras, provides some good historical information on early shutters.