4

Talking Motion Pictures

The repercussions of sound being added to motion pictures had an impact on every aspect of filmmaking technology. In some cases, it was necessary for aspects such as the screening speed to be standardized or to make changes in other major aspects such as the screening format, the negative editing systems and the re-printing systems, in addition to all of the system for colouring prints used in silent films.

The image always had to be the main feature, and this subordinate position has always been respected with regard to the adding of sound.

Silent Screen Era Sound

From the start, motion pictures had aspired to being equipped with sound.

Although the industry had to wait a total of thirty years to outfit itself with a true motion picture sound system, films never did without sound. The negatives might be silent, but the screening sessions had sound.

Distributors and producers competed with one another with regard to employing resources from the theatre repertory. From the presenter/narrator/commentator to a group of orchestra musicians, with choruses, soloists singing from sheet music composed expressly for the film. All of the music-hall and comic opera resources were used to accompany screenings, including the creating of "live" sound effects and, in some countries, the live dubbing of the voice by groups of actors.

In practice, the only limits placed on the media employed for this sound accompaniment lay solely in the producer’s and exhibitor’s financial means and the standing of the theatre in question.

Adding Sound & Film Preservation

A film is the recreating of an illusion of reality through the mechanical reproduction of images in movement. Adding of sound to the screening of silent films was in conflict with the actual state of the art at the time. In theory, the same film could be viewed every day in any theatre, but the accompanying sound depended upon the theatre involved, on the musicians/singers/actors and could be different every day. Silent films and their accompanying sound were two completely different realms as far as their aesthetics were concerned.

For preservation, the consequences of the existence of sound accompaniment for screenings were disastrous. When talking motion pictures first came out around 1927, the public no longer wanted to have anything to do with silent films.

Sound

SCREENING SPEED - (2. THE TALKIES ERA)

Flickering Picture & Continuous Sound

While the organs providing humans with their sense of sight solely transmit and process (perceive) one image at a time regardless of the number of parts of which the image is comprised, but without directly recording the changes which are taking place in its shape, brightness or colour, for the sense of hearing, each one of the Corti bodies which are struck by the vibrations vibrates in response to the sound frequencies specifically affecting it completely separately from the rest, one individual organ or group of organs being able to separately continue resounding throughout the entire length of time that the frequency to which it responds continues without their being affected by other organs starting or stopping vibrating.

Hence, the mechanisms invented for screening images in movement must be based on the consecutive reproduction of still images while those invented for playing back sound must remain on (running) throughout the entire time that the sound in question is being played back.

One Single, Constant Speed

In principle, except when attempting to create certain effects, sounds and images must be reproduced at the same speed at which they were recorded/filmed.

In the silent screen era, a great deal of attention was not devoted to maintaining the same speed throughout filming and screening, and later silent films have normally been screened at soundtrack speed.

The characteristics of the sense of sight make it necessary to change the screening speed solely with regard to the rate of movement, this being a change which can be dealt with and, in practice, is the case, for example, in the films from the silent screen era which are normally screened at 24 i/s without any unbearable consequences for the viewers’ senses, it even being possible to make much greater changes, such as that of reversing the order in which the frames are projected, without making the images unintelligible.

As regards sound, any changes or irregularities in the playback (or recording) speed are also readily noticeable, but this change not only entails the frequencies.

The changes in tone and harmony lead to it sufficing for the screening speed to be sped up by three frames per second for the sound to change completely and, of course, if the direction is reversed, the sound becomes unintelligible.

Musical Frequencies on the Diatonic Scale - Key of C
Middle "C" on piano keyboard	D	E	F	G	A	B	C*
264	297	330	352	396	440	495	528
On speeding up the playback rate from, for example, 26 to 36 images per second (a change similar to that which is involved when showing silent films at 24 i/s), a 330-cycle E note would sound like a 495-cycle B note.

Separate Reading, Feeding and Recording

All sound reproduction systems are equipped with built-in mechanisms for ensuring that recording and playback are done at the same, constant speeds.

In filmmaking, it is additionally necessary for the image and sound speeds to be totally in sync or exactly the same.

Except in some motion picture cameras (invented mainly for filming newsreels) and in those used in electronic filmmaking, the picture-filming equipment and the sound-recording equipment are separate from one another, although they function in sync.

With regard to reproduction equipment, from the Kinetoscope and disc-synchronized projectors to the modern ones and even to the electronic imaging systems, the picture and sound heads are mounted in the form of one single assembly equipped with the required speed-synchronization systems.

Screening Speed for Talking Motion Pictures

The standardization of the speed of 24 frames per second provided a solution (with double-blade shutters) to the flicker caused by the opening and closing of the shutter and also entailed a major rise in the price of prints which then took up 50% more film strip to make one same length of motion picture. It was inevitable that this rise in price meet with approval.

Twenty-four frames (456mm/second) was the minimum length necessary for the sensing speed of the existing optical sound systems, combined with the picture sharpness-related limitations of the emulsions available for making prints were to come anywhere near the possibility of recording and reproducing the frequencies of up to 5000 cycles which are necessary for achieving the minimum required degrees of sound reproduction quality.

It was also necessary to design and/or revamp all of the filming and screening equipment by changing their operating speeds and installing motors.

Cranks became a thing of the past.

FACTORS CONDITIONING MOTION PICTURE SOUND SYSTEMS

The combination of the recreating of images and sound in filmmaking and the development thereof as a sector of the show business industry has conditioned and, in many aspects, has limited the objectives and the advancement of motion picture sound systems.

Amplifying

For a sound reproduction system to be functional it must, first of all, be powerful enough to cover a certain volume of space, and no system can be successful if it does not cover this volume of space providing acceptable degrees of quality. The necessary power can be as low, for example, as in some headphones, to cover the volume of the external ear, but in the filmmaking industry and insofar as this industry became a form of mass entertainment, the movie theatres grew constantly larger and, somewhere around the twenties, any motion picture sound system which were to be considered apt for use in the motion picture industry had to be capable of covering several thousand cubic meters.

The attempted solutions based on the mechanical properties of sound waves met with greater or lesser degrees of failure, the final solution lying within the reach of solely of the field of electronics.

Electronic Tubes

In 1883, Edison discovered that, inside the glass tube of a lamp, an electric current flows from the filament to a separately welded wire, bridging the gap between the two. Twenty years later, it was found that a flow of electrons took place between the filament and the receiving wire; and J.A. Fleming, returning to work with Edison’s tubes, replaced the receiving wire with a plate (larger than the filament), discovering that the flow of electrons took place when the plate was positively charged, and that this flow halted when the plate was negatively charged. This rectifier transformed an alternating current into a direct current.

Starting in 1907, Lee de Forest worked with these rectifier tubes by placing a perforated plate in between the filament and the plate. This triode gave rise to a surprising effect of increasing the intensity of the flow of electrons fivefold.

Encouraged by the prospects of the development of radio broadcasting, in 1919, De Forest was finally able to build amplifiers capable of providing an intensity which would suffice to cover a large movie theatre.

From Head-On Listening to Stereophonic Sound

In the early days of talking motion pictures and for many years thereafter, the two-dimensional quality of the image on the screens was related to the head-on sound projection as a result of solely one speaker being installed behind the screen, and to the inevitable monophony involved on availing of solely one single soundtrack. In 1953, Cinemascope with stereophonic made its debut, incorporating four magnetic soundtracks but, just like in the Todd-AO for 70 mm films and the first "stereo" systems on optical tracks, the speakers were still positioned behind the screen.

In the eighties, systems began to be researched to incorporate side speakers and surround-sound which would be perfectly capable of providing an absolutely real sound space, but the two-dimensional quality of the picture on the screen continued to be conditioned by the development of these systems, which, generally speaking, with the exception of the films screened using large-format 3D systems, continued to be used for reproducing the sweetening (effects) of the scene.

Synchronization

Throughout their development, motion picture sound systems have always had to meet one specification, that is, to ensure that the sound would be heard in complete synch with the picture.

The Lumière system, on implementing a feeding system based on alternating stop/start sequences, made it difficult to synchronized picture and sound and to keep them in sync with one another. The celluloid film strips punched with sprocket holes (designed for the Kinetoscope, through which they were fed at a constant speed) did not hold up well under the hard work to which the alternating feed mechanisms subjected them and often tore apart. The disk and roller-based sound systems were not able to overcome this stumbling block.

The incorporation of the sound tracks onto the same film strips as the picture solved this problem for once and for all. Any tearing of the film strip and the resulting repair affected the image and sound to the same extent but did not affect the synchronization.

For some years now, new disc-based digital sound systems have been being marketed, but the disc-scanning mechanism is controlled from a signal track located on the film strip proper.

Advance (Sound/Image)

The existence of two read heads on one same reproduction system makes a gap (advance) necessary between the image and sound recordings at each given point in time.

In principle, each system located the sound on the film as it best saw fit. Hence, the Phonofilm positioned it behind the image (approx. 14 frames behind) and the reader above the picture gate.

The approved standard situated the sound ahead of the matching picture (by 21 frames) and the head beneath the projector window.

This standardization is not totally strict, shifting in position of up to 2 sprocket holes on the strips of prints currently meeting with acceptance and, in some cases (for prints to be screened in very long theatres), somewhat shorter lags have been used to offset the length of time that the sound requires to travel throughout the theatre from the screen speakers.

For 16mm films, a 26-frame advance is used. On the magnetic tracks, the sound lags behind the image, positioned 28 frames behind it in 35mm and 16mm, and 24 frames behind in 70mm films.

OPTICAL SOUND

Optical motion picture sound is one particularly brilliant solution to the difficult problem of incorporating a totally new component into a currently existing system by implementing the least possible number of changes and employing said system’s own technical language.

The sound is recorded and reproduced as an image and is photographed, developed, edited and printed using procedures similar to those used for the rest of the images.

Recording / Reproduction -- Photographing the Sound

The principle on which optical sound-recording systems operate is quite simple. A microphone picks up the sound waves, where they undergo modulation (proportional to the waves in intensity and frequency) in its power pack. The intensity of this electric current is stepped up to the power necessary to move the systems (mechanical or magnetic), which will modulate the intensity, the direction or the width of a beam of light. Said beam of light, which is focused by means of a micro lens, prints a strip of film which is moving at a constant speed (456mm/second) sketching a series of "spots" of light which reproduce the intensities and frequencies of the original sound in their density or their width and in their rate of change. Following developing and fixing, this photo film will bear the negative, on a lengthwise track, of the modulation of the light to which it has been exposed.

Turning Light into Sound

The reproduction system is likewise simple and substantially well balanced.

The sound negative is photographically reproduced on the prints.

In the screening systems, a beam of light of a constant intensity shines through a micro lens which focuses it onto the sound track of the film that is running at the same speed as during recording. The fluctuations in the transparency of the soundtrack will modulate the amount of light, which shines through it onto a photoelectric cell positioned on the opposite side of the film.

In response to the light to which it is exposed, this cell creates a flow of electrons, which, after being amplified, is routed to the speakers that will restore the sound vibrations to their original form.

Sound Systems

All of the patents and processes employed for optical sound can be broken down into three major groups: variable-density systems (fixed area width), variable area systems (fixed density) and digital systems.

Both the variable-density as well as the variable-area systems are analogue systems, and their fluctuations along the length of the track are, as regards a greater or lesser degree of transparency, a reflection of the fluctuations in the intensity of the sound waves and, with regard to the rate at which these variations take place, a reflection of the sound modulation.

In the variable-density systems [2], the photographic density is uniform over the full width of the sound track, yet varies along its length. In the variable area [1] systems, the sound track is constant in density, it being possible to say that each cross-section of the track is divided into two areas, one of which is theoretically opaque and the other transparent, and the relative width of these areas varies lengthwise.

The number of sound tracks varies depending upon the patents in question, there being single-track and dual-track systems and even systems of up to 13 identical tracks. In the eighties, stereophonic systems equipped with two separate tracks were marketed for the first time.

In digital stereophonic systems, the image encodes (under a graphic display) the binary codes, which will be converted into a sound signal by the scanning devices. The optical signal incorporated into the film in the disk-based systems contains a code, which controls the movement of the disk reproducer.

Compatibility

Since the standardization of the track dimensions and of lag, all of the patents and systems have been made strictly compatible and are reproduced using the same systems. A solution has been provided to making these systems compatible with digital, stereophonic systems by equipping the reproduction systems with sensors that detect the design features of the tracks and afford the possibility of deciding which to use. The modern tracks usually incorporate several sound systems by combining an analogue system with one or more digital systems.

MAGNETIC SOUND

Magnetism & Electricity

Although magnetism is a property common to all atoms, in most materials, the magnetic regions of the minute magnets in atoms are pointed in all directions, almost totally cancelling out the material’s magnetic properties. Iron, nickel, cobalt and some other (ferromagnetic) materials possess the property, in the presence of another magnetic field, of being able to point their atomic magnets in a certain direction and, to a certain extent, to keep them pointing in said direction permanently.

Following its being pointed in a certain direction, the material shows magnetic polarization and all of the properties inherent to a magnet. In 1831, in one of the scientific experiments of the most far-reaching importance which has ever been conducted, Michael Faraday discovered that an electric current which is running over a coiled wire around one section of an iron ring creates a moving magnetic field which, on opening and closing, generates a flow of electricity in another wire wound on another part of the ring. To the contrary, a permanent magnet, which is moved inside a coil of wire, generates an electric current.

It would be upon these principles that the functioning of electric motors and of magnetic sound-reproducing systems, among a long list of other apparatuses, would be based.

Systems & Media

The first attempts to put the fluctuations in the magnetic field to use in the reproduction of sound date back to 1881, but it would be Valdemar Poulsen who would achieve efficient wire recordings, in 1896-1903. During World War II, German engineers invented a system, which actually functioned on paper tapes coated in metallic oxides. Later, plastic (acetate, PVC & polyester) tapes were used with one side coated with oxides or metallic mixtures.

In filmmaking, mag stock is basically used in 35mm and 16mm perforated film bases or in unpunched (plain) films on rolls or in cartridges as working elements for processing sound. The first stereophonic scope system also employed magnetic tracks adhered to the picture film in prints, as well as in 70mm, 16mm and 8mm.

Magnetic Sound Recording

Magnetic recording and reproduction comprise a simple, totally well balanced system. The sound waves are picked up by a microphone which creates a modulation (proportional in intensity and frequency to the original waves) in is incoming power supply.

The electric current is amplified to power the recording head, which is comprised of an electric magnet, past the head gap of which the film strip bearing the magnetically neutral emulsion runs. The changes in intensity of the electric magnet will train the metallic dipoles of the emulsion in the same direction (to a greater or lesser degree depending upon the intensity of the signal) and the resulting track of trained particles will comprise a magnetic (analogue) representation of the intensities and original sound modulation.

For reproduction purposes, the magnetic track is run (at the same speed as the recording speed) past the electric magnet from which the electric charge has been removed (therefore being demagnetised).

The fluctuations in the magnetic field create electrical fields in the electric magnet, and the resulting current is amplified and then routed to the speakers to reproduce the sounds.

The way in which the digital systems which have come out on the market since the eighties is basically the same, but the signal is recorded by means of coded pulses which, in some cases, afford the possibility of separately managing set intensities and frequencies.

Image Format

IMAGE AND SOUND AREA & PROJECTION FORMATS

Although the image area and screening format concepts frequently tend to be confused up with one another, they are two different aspects. The former of these two concepts has to do with the surface area of the emulsion-coated area, which is used, for filming the image; and the latter refers to the dimensions and proportions of the image on the screen.

Image Area (Camera Aperture)

The dimensions of the filmed image area are always slightly larger than those of the image actually screened, but the differences between these two areas are not limited to these alone. Numerous anamorphic and flat widescreen systems employ negative and print stock based on marked differences. There are systems (such as those used in 65mm/70mm negatives or in those known as Super-35) from which 70mm flat widescreen or 35mm anamorphic prints can be made.

Lastly, the actual relationship between the image area filmed in negative, that which is reproduced on the prints and the format shown on the screen depends upon the lenses used during shooting, filming, printing and screening and upon whatever clipping may have had to be done due to the gate catches in the camera and projector.

Sound Area

When discussing the dimensions of the sound area, one must distinguish among three concepts: the sound reserve or area, which runs from the edge of the sprocket holes or of the film up to the image area; the sound track or column and, lastly, the area scanned by the sound heads, which is slightly wider than the sound column.

Screening Format (Projector Aperture)

For safety reasons (to prevent the actual edges of the image area from being seen on the screen), the area photographed on a negative and reproduced on the print is larger than that which will actually be shown on the screen in movie theatres.

The main standards set concerning the dimensions of the image area have actually been drafted taking into consideration the dimensions and the proportional ratio of the aperture of the catches on the projectors, which are those which shut out the beam of light of the projector and determine the screening aperture.

35MM IMAGE AREAS AND STANDARD FORMATS

Silent Film or Full-Aperture Format

In silent films, the image filmed in each frame could fill the entire surface area between the rows of sprocket holes and between the edges of the consecutive frames. It is generally-accepted that the area set aside for the image measured 24mm x 18mm in the silent screen era and was centred perfectly on the axes of the frame, but the lack of standardization, the almost totally hand-crafted basis on which most of the manufacturers of motion picture cameras were working and, above all, the nature of their not being a fundamental component for the motion picture business and the screening which characterizes the image area gave rise to a situation in which absolute freedom of choice was employed, in which the height and width of the frame could vary almost from one camera to the next.

Nevertheless, in the silent screen era, an aesthetic criterion came into being regarding the screening format based on the 1:1.33 proportions.

In the past twenty or thirty years, shooting with full-aperture (Super 35mm) cameras, which use the entire area between sprocket holes for the frame on the negative, which can be printed by anamorphic compression or enlargement, in individual shots or sequences, or cut to the desired format, has become widely-used.

Introduction to the Sound Area

Along with the standardization of the screening speed, the major technical impact of the adding of sound reproduction to filmmaking was the compulsory modification of the area devoted to the image on films.

The positioning of the sound area next to one of the rows of sprocket holes made it necessary to shift the position of axis of the image horizontally and to reduce its area. The sound area takes up the safety gap between the image and sprocket holes and takes up a total width of approximately 3mm.

The theoretical 24mm of the silent film format were cut down to approximately 22mm, the aspect ratio (on 18mm / 22m, the aspect ratio would be 1: 1.22) being changed. The industry, placing priority on keeping the proportions the same above and beyond the more effective use of the emulsion on the filmstrip, cut down the area of the image area even further, enlarging the space between consecutive frames.

"Academy" or Standard Format

In principle, the image area continued to have precisely an aspect ratio of 1: 1.33 of silent films, but, in short, the "Movietone" area won out and, measuring 16.03mm in height by 22.05 mm in width, slightly modified the aspect ratio to 1: 1.37.

Nevertheless, the screening format is still not a "key issue" and, therefore, mention must be made of the fact that the above-mentioned standard measurements which were those proposed by the Hollywood Film Academy do not tally with those stipulated under the international ISO standards, which differ slightly (16.00 / 21.95mm), but which are in keeping with the same aspect ratio.

Widescreen Formats

The efforts made to make motion pictures more spectacular led to the development of formats and even film gauges and entire filming and screening systems, which, generally speaking, revolved around enlarging the size of the screen.

In the systems based on the screening of one single 35 mm film, two different techniques were developed.

"Scope" or Anamorphic Formats

The "scope" systems are based on the filming of the image by changing its aspect.

The approved standard is in keeping with the Cinemascope compression criteria, using lenses (which are normally cylinder lenses) to achieve a compression ratio (enlargement ratio for screening of "x2". The "scope" frame is standardized at 18.16 /21.3, with an aspect ratio (unsqueesed) on the screen of 1:2.34.

Other "scope" systems employ different schemes for filming and for making prints. In Technirama (perhaps the best possible system for anamorphic images), the negative was shot on 35mm film, which was run horizontally through the camera, creating frames having eight sprocket holes. The image was put through two anamorphic processes (during shooting and on making prints) leading to the same total compression (x 2) and being projected using standard systems.

Finer-grained colour emulsions being put on the market in the sixties made the invention of 2-standard or "two-pi" systems possible, which used the space for two sprocket holes for each frame. In Techniscope, the negative was filmed using revamped cameras, which took solely two sprocket holes and conventional plus/minus lens assemblies. For making prints, the frames were enlarged vertically up to the point of taking up four sprocket holes and, for screening purposes, were blown up again (horizontally), thus achieving the nominal ratio of the rest of the "scope" systems.

Flat Widescreen Formats

The success of the scope formats and other commercial reasons boosted the launching of flat widescreen scope formats filmed using conventional plus/minus lenses, in which the space between frames is enlarged even further and a major part of the emulsion-coated surface of the film was not used to full advantage. Three of these formats have become popular on a wide-ranging basis under several different names. Their screen aspect ratio: 1:1.66, 1: 1.75 and 1:1.85. It was at the opposite end of the range of these scope formats, which cut down the actual size of the frames that "Vistavision" was located. In Vistavision, in negative and positive, the frame took up eight sprocket holes. This system met with failure due to the need of revamping the projectors to run the film horizontally and eight sprocket holes per frame.

Other Scope Formats

The 70 mm film width affords the possibility of filming in scope format using plus/minus lens assemblies and of filming some extremely high-quality shots. Adhering to ISO standards, the catch dimension for projection purposes are 22.10 mm / 48.59mm with 1: 2.20 an aspect ratio.

It is a relatively frequent practice to film in Super 35mm (total aperture) using anamorphic lenses, to make copies in 35mm scope or in 70mm flat format.

For the Super 16mm format negatives, the image field extends over into the sound field on the prints. These negatives (flat format negatives) are copied in 35mm scope format at 1: 1.66.

4.2.3. - IMAGE AREA, FORMAT DIMENSIONS AND ASPECT RATIOS

The measurements given below have been taken from the ASA and ISO standards given that these two standards differ solely to a minor degrees

FORMAT &

NOMINAL ASPECT RATIO

CAMERA

SCREENING

Distance to Reference Edge

Surface Area of Image Filmed

Surface Area of Image Screened

Aspect Ratio

35mm SILENT (1) 1'33

NORMAL (2) (a) 1'37

NORMAL (3) 1'37

------------

(b) 18'75

18'00 / 24'00

16'03 / 22'05

16'00 / 21'95

17'25 / 23'00

15'25 / 20'96

15'29 / 21'11

1'33

1'37

35mm (Wide screen) (2) 1'85

1'75

1'66

(3) 1'85

1'75

1'66

Vistavision (5) 1'75

Cinerama (6)

(b) 18'75

------------

(4) / 22'05

(4) / 21'95

22'10 / 37'52

------------

11'33 / 20'96

11'96 / 20'96

12'62 / 20'96

11'33 / 21'11

11'96 / 21'11

12'62 / 21'11

21'31 / 37'29

27'64 / 75'06

1'85

1'75

1'66

1'86

1'76

1'67

1'75

2'71

Cinemascope (S.mag.) (2) 2'55

Cinemascope (S.opt.) (2) 2'35

"Scope" (3) 2'35

Technirama (5) 2'35

Techniscope (5) 2'35

(b) 17'50

(b) 18'75

------------

18'67 / 3'80

18'67 / 22'10

18'60 / 21'95

23'80 / 37'15

9'34 / 22'10

18'16 / 23'16

18'16 / 21'31

18'21 / 21'29

18'16 / 21'31

(d) 2'55

(d) 2'34

(e) 2'34

(f) 2'34

16mm (2) 1'33

(3) (g) 1'33

S16mm (3) (h)1'66

(b) 7'97

7'49/10'26

7'42/10'05

7'42/12'52

7'21/9'65

7'26/9'65

------------

1'33

1'32

------------

70mm 65mm. (3) 2'20 70mm. (2) 2'20

70mm. (3) 2'20

(b) 34'95

23'00/52'50 23'00/52'60

23'00/52'50

------------22'00/48'60

22'10/48'59

------------

2'21

2'20

(1) Dimensions not standardized, not even as a reference (2) ASA (3) ISO (4) Dimension not standardized for negative, not even as a reference. (5) Dimensions not standardized. (6) Cinerama on three bases (plus a fourth base for the eight sound tracks). The image was incorporated in three frames of 27.64/25.07 (on 5 sprocket holes). The actual projection format (1:2.71) was masked by the curvature of the screen, which cut the perception of the proportions to 1:2.2.

(a) Dimensions standardized for negatives and prints are for the "Movietone" format, the ratio for the proportion of which is 1.37. (b) Between reference edge and axis of the image field. (c) Between edge of reference and edge of image field. (d) Unsqueezed image on screen. (e) Unsqueezed image on screen. (f) Unsqueezed image on screen. (g) The dimension given is solely as a reference. (h) 16mm "W" type.

4.2.4. - SOUND TRACK DIMENSIONS

Measurements taken from the standards issued by the International Standard Organization (ISO)

SIZE FORMAT & SYSTEM

From axis to edge of reference

Sound Area

Sound Track

Scanned

Area

35mm Variable area

Variable density

Scope magnetic (a) Track 1

Track 2

Track 3

Track 4

35mm sep-mag 3 tracks - Track 1

Track 2

Track 3

4 Tracks -- Track 1

Track 2

Track 3

Track 4

6'30

1'02

5'36

20'18

33'99

8'60

17'50

26'40

7'90

14'30

20'70

27'10

2'99

------------

1'93

2'54

1'60

0'97

1'60

5'00

3'80

2'13

1'27

0'635

1'27

------------

16mm Variable area

Variable density

Magnetic (1)

1'48

14'55

2'95

1'52

2'03

2'55

1'80

2'15 (2)

70mm Magnetic (b) --- Track 1

Track 2

Track 3

Track 4

Track 5

Track 6

1'42

4'22

9'47

60'52

65'77

68'5

4'80 (3)

0'80

4'80

1'25

8mm Magnetic

S 8mm Optic

Magnetic (1)

0'40

7'57

7'58

0'90

0'67

0'50 (4)

0'68

0'48 (2)

0'66

0'53 (2)

(1) The 16mm and S8-format films with magnetic sound can have another track attached for balancing the rolling. This track, located between the sprocket holes and the edge, is not used for recording sound. (2) Head gap or universal dimension. (3) Sound tracks 1-2 and 5-6 go on one same magnetic strip. (4) Modulated area width. The recorded field can be up to 0.75 in width.

(a) Relationship of tracks to speakers in theatre: track 1, left; track 2, centre; tract 3, control or auditorium; track 4, right. There was a variation on magnetic-optical prints, which has an optical sound track measuring 0.97mm in width located between track 2, and the picture. (b) Relationship between the tracks and the theatre: track 1, to left of screen; track 2, centre left; track 3, centre; track 4, centre right; track 5, to right of screen; track 6, control signals or environment.