PROJECTION ~ How it all works

ABC Chester projection department 1965

ABC Chester projection department 1965



Early Projection~ Gearing Up.
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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 on the central (TMS) server it can be moved to each individual server in any screen.

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 Ellis©


Film Stock

When 35mm film was introduced in the 1896 it had a nitrate base that needed to be handled with great care. If not there was a strong possibility that a fire could take place as the base was highly flammable. No smoking in the projection room was strict requirement. It was because of film bursting into flames that separate projection rooms became a requirement from 1910.

Nitrate film

Before this, equipment was placed in the same area as the audience. A separate rewind area was also a requirement. Film that was only going to be projected was allowed in the box.

Safety base film arrived in the 1950s and some cinemas then did the rewinding in the projection room using the old rewind area for other things. Though the film was a safety base, no smoking rules still applied. In the silent days the full frame was used. In other words the area taken up by the soundtrack that came later, was part of the image. This ratio was known as 1.33:1. When sound arrived because of the soundtrack, a plate masking the soundtrack area had to be used. This meant there had to other adjustments so the picture could still be projected on to the same screen. This involved cropping slightly and using another lens. The film makers didn’t like their images being cropped so in 1932 The Academy ratio, 1.37:1 was introduced. This was near the 1.33:1 ratio. Slight changes to the frame area was required.

In the 1950s wide screen was introduced. There were several wide screen ratios. Film makers when shooting in a ratio they knew would be cropped would shoot with microphones in the frame. Many filmmakers knowing part of their images would be cropped were happy to shoot with objects in shot that would be cropped later. There was 1.85:1, 1.66:1 1.75:1. 1.66:1 consisted of thick frame lines. Disney shot a number of productions in this ratio. This ratio left very little room for framing (racking). Wide screen gave the impression that the picture was bigger than Academy (1.37:1),which it wasn’t. You could show an academy ratio film in wide screen, using wide screen plates and lenses but some of the image would be cropped, for examples titles missing. Otherwise it looks like any other wide screen presentation. So there is more picture area with academy than a 1.66:1 wide screen image.

In 1953 Cinemascope arrived. This used the anamorphic system. It was shot with an anamorphic lens and shown with one. In the early days of scope there would be annoying lines that would appear as a flash at the top of the screen when there was a cut to another scene. These were joins made by the neg cutter,which couldn’t be cropped as there was no margin for it. Early anamorphic systems distorted the image slightly. With cinemascope came four track magnetic sound. Prints carrying these tracks also carried an optical track, which was reduced in size and volume levels were lower than normal optical tracks. The mag head was placed above the projector head unlike the optical, which was below. The operator had to be careful that the tracks were not magnetized. Films with magnetic tracks had smaller sprocket holes, known as Fox Hole. The projectionist had to make sure the sprockets were changed for this.

Scope required a backing lens and an anamorphic. Some Cinemas had a separate backing and anamorphic lens, others had them combined. If you mistakenly left the wide screen lens in and put the anamorphic in front of this there would be a very large image that would spread beyond the screen area,some projected on the front exit doors. A cinemascope image is a stretched image that covers, apart from the soundtrack area the whole frame with thin frame lines. The anamorphic unstretches the image to make it look normal. Apart from a change of lens the masking plate or aperture plate also has to be changed.

With four track magnetic, speakers were placed at the right, centre and left of the screen. There were also speakers on the side walls which played the effects track. 70mm film also carried magnetic tracks but there were six, giving even more realistic sounds. Cinerama had seven tracks played using a separate reel carrying the tracks. Years before Walt Disney produced Fantasia, carrying optical tracks on a separate reel for stereo. Another format in the fight against television’s affect was third dimension (3D). Two 35mm projectors ran together both carrying 5000ft of film. These films required an intermission as only fifty minutes could be screened in one go. Some cinemas found it a problem because of the length of time carbons would burn. Cinema engineer Jim Shultz said the best for this was the Peerless carbon arc. Glasses were required to view but some found them a strain and the novelty soon wore off.

In the 1970s Dolby Stereo came along. This wasn’t magnetic but an optical track carrying information for four channels. Later, Dolby Digital came on board, the sound head being above the projector head. DTS was another system. A compact disc would keep sync with the film. There was time code that meant even if a join was made sync would be kept, unlike the sound on disc days of early sound where a blank piece of film would have to be inserted. Exciter lamps with white light were used for optical sound until the red reader came along. Some say that the red reader doesn’t produce sound as well using the old tracks that were designed for the white reader.

Following on from safety base film there was polyester stock, which was so strong it was possible to pull a machine over. This stock prevented film breaks and the cry of ‘put a shilling in the meter.’ The cinema went through many changes. From two projectors to long running equipment and format changes, for example 70mm Imax with fifteen perforations to a frame and horizontal projection. Years before there was 35mm Vistavision, which some theatres projected horizontally. Also new sound systems such as Dolby Digital. All that technology has been cast aside to make way for digital. What will follow digital? A good question. What can follow something like that. I think from now on it will always be digital but improvements will be continually made.

David A Ellis©



Simplex Projectors
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PHILIPS MOTION PICTURE PROJECTOR ~ click on this frame to read




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 was 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.