PROJECTION ~ How it all works

ABC Chester projection department 1965

ABC Chester projection department 1965


Projectionists are now a dying breed. Digital projection has now replaced film worldwide. This means the projectionist of yesteryear is no longer required. Cinema managers are now trained to operate the equipment. When films were projected in converted halls and fairgrounds in the early part of the 20th century, the projector, projecting inflammable 35mm nitrate film stock was often placed in the aisle. Often there would be no take up spool; the film falling into a basket. In 1909, because of many fires, the cinematograph act was introduced. This came into force on 1st January 1910 and projectors had to be placed in a fireproof projection room with fire shutters over the projection ports. A bucket of sand, a bucket of water and an asbestos blanket also had to be placed in the projection box. If there were a fire, a fire record would be played letting staff know, but not the public, preventing panic. The staff on hearing the tune would then get the public safely out. In many cases the public were totally unaware that there was a fire.



35mm film has four sprocket holes each side to a frame, and there is sixteen frames to a foot. Because there are four sprocket holes, the film must be laced in frame or rack. All machines have a framing or racking handle that moves the intermittent sprocket, allowing framing to be adjusted. Normally the framing handle wouldn’t need to be moved unless the picture was out of frame. Projectionists would have to adjust the framing, if for example a 4×3 ratio picture was shown in wide screen ratio. The framing sometimes had to be adjusted to show heads that were missing due to it being shown in the wrong ratio. Unfortunately many cinemas only had two ratios, scope and wide screen – and then only one wide screen and scope ratio. A few were equipped for several ratios, so avoiding cropping heads and titles. In fact a 4×3 ratio film had more frame area than wide screen ratio film. With a 1.66:1 ratio, often used by Disney there were thick black racking lines, so the picture area was a lot less than 4×3. Because the picture was screened wide screen it gives the impression you are looking at more picture, which you aren’t.   A projectionist, when screening a film had to stand by the projector at all times, holding the handle (dowser), which closed off the light. To screen a feature two projectors were required. Rolls of film on wooden and later plastic bobbins were shipped to the cinema. The projectionist or operator would join two 1000ft rolls together, giving twenty-two minutes running time. Films would be joined using a splicer and film cement. The operator would scrape the emulsion off one piece of film and rub the shiny side, and then put the cement on, which was a strong smelling liquid. The splicer would bring the two pieces of film into contact, hopefully making a strong join. Much later, tape joiners were employed. In the nitrate days a feature lasting around ninety minutes would consist of ten rolls of film.


In the 1950s, safety base film arrived and rolls were sent in 2000ft rolls. The films arrived in a metal transit case, delivered by Film Transport Services (FTS). Films were sometimes shipped by rail. The rolls were housed in tin cans, later changing to plastic containers. The rolls of film were transferred on the rewind bench to spools.

The Projection Room

Projection room~ TATLER/Classic

Projection room~ TATLER/Classic

The spools are placed in the top spoolbox of the projector and the film is threaded or laced by the projectionist through the projector and sound head, then placed into the take-up spool. Loops are made to allow for the stop/start motion of the film. If there weren’t any loops the film would just break. The 35mm film runs through intermittently at 24 frames per second (fps), 18 inches per second or 90feet per minute, which gives 22minutes-running time on a 2000ft spool. A flicker shutter was employed to cut light off when the film was in motion. Some projectors had front, some rear. If the shutter went out of sync (out of phase) there would be streaking that was very noticeable on light scenes and titles.

The sound is nineteen and a half frames ahead of the picture. It can’t be printed where the picture is shown due to the intermittent movement. Carbon arcs used to provide the light source. There was a wide choice of lamp houses. These included the Kalee Vulcan, Kalee Regal, Ashcraft, Mole Richardson, Kalee President, Kalee Lightmaster and Peerless Magnarc. The President and Lightmaster would often accompany the Kalee 20/21 machines. The carbon arc consisted of a mirror to reflect the light and a motor to feed the carbons. A card placed on the top of the lamp house allowed the operator to see if his carbons were adjusted correctly. In large halls some projector gates were water cooled because of the high amperage. The Mole Richardson lamp house was water-cooled. Rectifiers were used to convert AC to DC for the carbon arcs. Some were solid rectifiers, placed behind the projector, others were the mercury type.

Click on the frame below to understand the basics of how a 35mm cinema projector worked

Traxler video


Click on the frame below to follow the lacing of 16 projectors interlock using  just one film


Click on the frame below to follow the lacing of IMAX film projector

David Ernst video



Mercury Rectifiers

mercury rectifier

The mercury arc rectifier looked like something from a science fiction film. It was a bulb filled with mercury, which glowed. Some cinemas had one rectifier so a light drop would occur when striking the second arc. Some had two Later, many switched to xenon lamps. Some carbon arcs were converted to xenon, for example the Peerless. A changeover system was employed to change from projector one to projector two, without creating a break. Cue marks covering four consecutive frames were printed on the film, which would appear in the top right hand corner of the screen. These let the projectionist know when to changeover. Some projectionists would add their own cues adding crosses that almost covered the frames. Punching holes in the frames was another practice by bad projectionists. On the first cue the operator would start the motor and open the lamp house douser. Eight seconds later the over cue would appear. The projectionist would then open the shutter and change the sound over. A good changeover would look like a scene change.






Some cinemas fitted automation units, such as Projectomatic, originally Essoldomatic, invented by the Essoldo cinema chain, which controlled changeovers, tabs, house lighting and non-sync. Projectomatic had one drum that had pins in it, which operated switches that did the various operations. To activate the drum, silver tape was attached to the film. Cinemation (pictured above) was a more advanced system, the brain child of Bernard Bentley, and installed in Rank cinemas, using two drums. This could do all that projectomatic could do and more. Cinemas went on to fit long running equipment. This was the end of the changeover for those cinemas. There was the tower system where the film had to be rewound and a non-rewind system known as a cakestand. The projectionist had to be careful with these systems as the film was run through rollers around the projection box before being threaded.

The projection team at work during the 40s The Chester Odeon projection team 1940s


Odeon Chester BTH SUPAS~ Single Unit Projection Assembly

There were many makes of projector.Among them was British Thomson Houston (BTH), which all Odeon cinemas installed. Odeons first employed type A projectors with type B arcs. Later, in the 1940s they installed the SUPA, which stood for single unit projection assembly. This machine had everything built in; including amplifier and the take-up spool ran anti clockwise. Later, many Rank cinemas used Kalee 21 machines before using Cinemeccanica in the mid 1960s. Many installed the dual gauge Victoria 8. Associated British Cinemas (ABC), mainly used Ross projectors. Later, they switched to Philips FP20s. Philips also produced two dual gauge 35/70mm machines, the DP 70 and 75. The 70 was the only projector to win an Oscar. Simplex was an American machine and one of the good things was the masking or aperture plate could be changed while the machine was running. Westar and the range of Kalee projectors were also popular. The Rolls Royce of Kalee machines was the Gaumont Kalee 21, arriving in 1947. These would be employed in nearly all Gaumont Theatres. Many of their theatres had previously used the Gaumont Eclipse machine with a sixteen-inch turntable on the back, used for sound on disc. The discs ran at thirty-three and a third RPM but the stylus was placed in the inside, at the end on a conventional disc.

Sound Systems

RCA sign from the Tatler/Classic, given to Roger Shone by Jack Lightfoot, the final chief projectionist.

RCA sign from the Tatler/Classic, given to Roger Shone by Jack Lightfoot, the final chief projectionist.

Sound systems included Radio Corporation of America (RCA), Western Electric, British Acoustic and British Talking Picture. Sound was optical, variable area and density being mono only. On an area track you could see the intensity of sound by the lines on the track. To get an optical track in sync the loop below the intermittent sprocket had to be the right size. If it was, a diamond, which is printed on the leader, would be in line with the optical system in the sound head. If the loop was too big, sync would be affected slightly. A lamp called an exciter lamp would be employed to focus on the track. This would shine on the track and would pass through a photoelectric cell, turning the light into electrical current that went to a pre amplifier before being fed to the main amplifier. Sound heads were usually designed to carry two exciter lamps, allowing a quick change if there was failure.


When cinemascope arrived in 1953 Fox released films carrying four magnetic sound tracks. The film also carried a half optical track. Theatres not equipped for four track would be sent an optical only print.  The sprocket holes were smaller on these prints and were known as Fox Hole. Strangely enough, films carrying these tracks were advertised as being in stereophonic sound when stereo is only two tracks and four would be quadraphonic. The sound head was above the projector head and with these prints you had to make sure you didn’t erase the track. Also shedding of the oxide could be a problem.



Stereo sound wasn’t new in cinemas, back in 1953. In 1940 Disney’s Fantasia was screened using four optical tracks on a separate reel. In the 1980s we had Dolby stereo. This was optical sound that carried four tracks and was split and fed to four amplifiers. The last optical tracks to be used were cyan tracks using what was known as a red reader instead of the original exciter lamp. DTS was used. This is a CD disc that runs in sync with the film, an advanced version of sound on disc. Even if the film were cut, sync would still be kept, because time code is used. There was also Dolby Digital. There was a digital sound head fitted above the projector head. Information was between the sprocket holes on the optical soundtrack side. Theatres that weren’t equipped for Dolby Digital could use the stereo optical tracks.

The projectionist had to put programmes together, keep an eye on the film running through the projector and make sure the light from the arc lamp was ok. Carbons could jam together making the picture fade to nothing. This problem was eliminated with xenon lighting, though some say the light isn’t as good as carbon arc.

In the 1950s projectionists were given several wide screen ratios to work with, including Cinemascope, which used a lens called an anamorphic to stretch a squeezed print to normal on a wide screen. There was a backing lens that was behind the anamorphic.





3 Dimensional


There was also 3D, where two 35mm machines loaded with 5000ft of film ran together. There was a break in the feature to allow two more 5000ft reels to be loaded. There was Cinerama where three projectors ran together with sound on a separate reel carrying seven magnetic tracks. 70mm was screened with six magnetic tracks printed on the film. 70mm also had five perforations to the frame.

A few years ago film stock changed to polyester, which is unbreakable. No more stamping of feet or ‘put a shilling in the meter’ because of a film break. Polyester is so strong that it could pull a machine over and still not break. In the early days rewind rooms had to be separate from projection rooms. In the nitrate days, and even in the safety base days, firemen would often inspect the projection areas and a strict ‘No Smoking’ rule was in place.

In the past there was the chief, second, third, fourth and trainee projectionist. Sometimes there was a co chief and co second. Because of safety base, towers, non-rewind systems and automation, many cinemas cut their projection staff, often having one man (single manning) running the show. For years they often had three operators on at any one time, even in a single cinema.

Many modern multiplex cinemas ran on single manning, one man/woman running several screens. This was possible because of sophisticated automation equipment using computers. Film stock and film projection equipment improved greatly to be suddenly thrown out in favour of digital.



A rather basic digital installation at the Sealand Road, Cineworld


Now all cinemas are equipped with digital projection, not a frame of film in sight. The plus side is no dirt, scratching or weave. No matter how many times it is screened the quality remains the same. A film can be screened in several auditoriums at the click of a mouse, no need for several copies. Once the film is in the server it can be moved anywhere.

I myself was a cinema projectionist and it is sad that this trade, like so many others has been confined to the scrap heap. There was something about handling film, and being able to physically see images. Showmanship where a projectionist could provide a fantastic cinematic experience has gone. Curtains (tabs), which hid a blank screen, are no longer used in cinemas. Curtains hiding the screen added to the cinematic experience. A blank screen doesn’t do anything for showmanship. Also masking, which masked the rough edges that were projected because of the masking (aperture plate) are no longer used in many cinemas.

I will miss film but in several years time people will only find it in museums. How sad.

DAVID A ELLIScopyright white




Early cinema projection.

Projection Room 1912

In the silent days before 1910 the projectionist was in the auditorium with the patrons. The projector would be in the aisle and the operator would operate the projector by turning an handle. The film would usually fall into a basket. The film was nitrate base so could easily go up in flames. This happened on numerous occasions. In 1910 it became law that projection equipment had to be housed in a separate area from the audience. So, cinemas had to construct projection rooms containing fire proof shutters. Also there had to be a bucket of water, a bucket of sand and an asbestos blanket, as fire precautions. The projection room had to be separate from the rewind area. Only film on the projectors was allowed in the projection box. This practice was kept until the introduction of safety base in the fifties. Then it was allowed to rewind film in the projection box.

Another strict rule was no smoking, and signs would be placed in the projection and rewind rooms. Staff in a projection room in the early days would be three or four people a shift. There would be one man turning the handle between sixteen and eighteen frames per second, another would be attending to the carbons, having to constantly feed them, as there was no automatic feed at that time. Another would be taking care of rewinding.

Sound on disc system

Projection work could be a little on the unhealthy side due to carbon dust being inhaled when cleaning arcs, carbon fumes being breathed in before extraction was fitted, possible exposure to asbestos, which was used on cables connected to the equipment, and the dangers of some early machinery with a front flicker shutter that wasn’t encased, and could do damage if contact was made. There were also cleaning fluids that were suspect where health was concerned and the dangers of rewinding poor prints that could make a nasty cut to your fingers.

In the nitrate days films were shipped in 1000ft foot rolls giving eleven minutes running time. These would often be joined together into 2000ft rolls by the projectionist, using film cement. Tape joiners were a long time into the future. Projection rooms varied in size, some having limited movement. In 1932 The Bioscope magazine reported on the opening of the Dominion Hounslow, stating that it has one of the largest projection rooms in London. It was equipped with Walturdaw and Western Electric sound.

1928 Ross 35mm projector

There were several makes of projector including Kalee, Simplex, Kamm, Empire and BTH, made in Rugby. Kalee machines were made in Leeds by Kershaws, and Simplex was made in New York by the International Projector Corporation. Exhibitors found themselves paying out huge sums to install sound. You could buy the disc and optical system or just the optical system. In 1929 a Cinephone disc and optical system cost between £1500 to £1950. Easy terms were usually on offer.

The cinema has come a long way from those early days. We have seen wide screens, 70mm, safety base film, polyester film stock, non rewind systems (cake stand) and towers, eliminating changeovers, magnetic sound tracks, Dolby Stereo, Dolby Digital and now digital projection. Most cinemas have removed their 35mm equipment and most has been skipped. Fortunately there is the Projected Picture Trust (PPT) who have saved equipment and have examples of all machines at their headquarters in Halifax.

David A Ellis©


THE American Simplex projectors made in New York by the International Projection company were installed in a number of super cinemas including the Paramount and Roxy in New York. They were also distributed worldwide. The New York Paramount had three machines and Hall and Connolly continuous feed high intensity lamps. It was reported that beneath the pedestal of each projector was a recessed, coveted pocket and outlet box from which the asbestos covered lamp leads are led up through the centre of each pedestal to the switch box and lamp. All the conduit being concealed gave the room an unusually neat and dignified appearance.

In 1923 the machines were installed at the London Palladium. The Holborn Empire was also equipped with them. In 1930 at The Carlton in Essex Road London they were installed with Peerless high intensity arcs and Thide electric change overs. The Carlton also installed the Brenograph effects projector. In 1928 at the Broadway Stratford four Simplex machines were installed with Ashcraft high intensity arcs. At the Astoria old Kent Road, London there were back in 1930 Western Electric sound and Hall and Connolly high intensity arcs partnered the Simplex installed by J Frank Brockliss.

Astoria old Kent Road

A report in the Bioscope magazine dated December 11 1929 says: Owing to the pressure of Continental orders, J Frank Brockliss Ltd, decided to enlarge their organisation in France. A completed stock of Simplex projectors, spare parts and similar projection equipment, such as the company handle in London, will be held in stock in Paris. In this manner excellent service is assured to the many Continental users of Simplex projectors, over one hundred of which have been installed during the past twelve months. Another Bioscope report from June 2 1921 says: In spite of depressing trade reports generally, the Imperial Film Company Ltd, state that Simplex projectors are selling briskly. Between May 15 and the end of the month, no less than nine machines were installed in London and the South alone; three at the Coronation Theatre Manor Park; two at the Prince’s Pavilion, Walthamstow; two at the Rivoli Whitechapel and two at the Savoy Picture House Plymouth. Since the Imperial Film Company Ltd started distrubuting the Simplex projector in Great Britain, son eighteen months ago, they have sold several hundred machines.

In the 1920s a Peter H Griffiths wrote a number of articles for the Bioscope magazine on the projection rooms of some of America’s finest cinemas. One of the theatres’ he dealt with was the Proctors theatre in New York, which housed Motiograph machines. There were round ports in this theatre. In March 1931 the Select cinema Redditch installed new G Model RCA sound equipment with Simplex machines and little known Hahn Goertz carbon arcs. Finally, the idea of a Cinemascope type picture was given a mention in the Bioscope of October 14 1931. It said: Last week, in four of the Paths Natan halls, public demonstrations were given, after each seance, of the Hypergonar. This is the original optical invention of Henri Chretien, for giving wide pictures by the projection of standard width film on which the images are compressed.

The Hypergonar gives expansion both horizontally and vertically. The images are not merely magnified, but optically extended without distortion. The best demonstration was that given at the Ermitage Pathe, where the Hypergonar was adapted by Brockliss and company to Simplex projectors. The demonstrations appear to have been highly appreciated by the public. Pathe Cinema S A has bought the world patent rights, and experiments are being made in the Pathe Natan laboratories Joinville. In the 1930s, cinemas were built with the coming of wide screen pictures in mind, building them with wide prosceniums, which didn’t accomadate wide pictures for several years. Could it have been the war and lack of money that held back the Cinemascope picture until the 1950s?

David A Ellis©