- This article is concerned with technical aspects of moving film projection. For non-film movie projection, see digital cinema. Digital cinema refers to the use of Digital technology to distribute and project Motion pictures The final movie can be distributed via For historical aspects, see the article history of cinema. The history of film spans over a hundred years from the latter part of the 19th century to the beginning of the 21st century.
A movie projector is an opto-mechanical device for displaying moving pictures by projecting them on a projection screen. Mechanics ( Greek) is the branch of Physics concerned with the behaviour of physical bodies when subjected to Forces or displacements Projection screens are installations consisting of blank surface and a support structure used for displaying a projected Image for the view of an audience Most of the optical and mechanical elements, except for the illumination and sound devices, are present in movie cameras. This article is about motion picture film cameras See Video camera for cameras which record images electronically
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Physiology
According to the theory of persistence of vision, the perceptual processes of the brain and the retina of the human eye retains an image for a brief moment of time. Persistence of vision is the phenomenon of the eye by which even nanoseconds of exposure to an image result in milliseconds of reaction (sight from the retina to the optic nerves The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain This theory is said to account for the illusion of motion which results when a series of film images is displayed in quick succession, rather than the perception of the individual frames in the series.
Persistence of vision should be compared with the related phenomena of beta movement and phi movement. Beta movement is a perceptual Illusion, described by Max Wertheimer in his 1912 Experimental Studies on the Seeing of Motion, The phi phenomenon is a perceptual Illusion described by Max Wertheimer in his 1912 Experimental Studies on the Seeing of Motion, A critical part of understanding these visual perception phenomena is that the eye is not a camera, ie: there is no "frame rate" or "scan rate" in the eye. In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also Frame rate, or frame frequency, is the measurement of the Frequency (rate at which an imaging device produces unique consecutive images called frames The Instead, the eye/brain system has a combination of motion detectors, detail detectors and pattern detectors, the outputs of all of which are combined to create the visual experience.
The frequency at which flicker becomes invisible is called the flicker fusion threshold, and is dependent on the level of illumination. The flicker fusion threshold (or flicker fusion rate) is a concept in the Psychophysics of vision. Generally, the frame rate of 16 frames per second (frame/s) is regarded as the lowest frequency at which continuous motion is perceived by humans. (Interestingly this threshold varies across different species; a higher proportion of rod cells in the retina will create a higher threshold level. Rod cells, or rods, are Photoreceptor cells in the Retina of the Eye that can function in less intense Light than can the other type )
It is possible to view the black space between frames and the passing of the shutter by the following technique:
Close your eyelids, then periodically rapidly blink open and closed. If done fast enough you will be able to randomly "trap" the image between frames, or during shutter motion. This will not work with television due to the persistence of the phosphors nor with LCD or DLP light projectors due to the continuity of image, although certain color artifacts may appear with some digital projection technologies. Digital Light Processing (DLP is a Trademark owned by Texas Instruments, representing a technology used in projectors and Video projectors It was A video projector takes a Video signal and projects the corresponding image on a Projection screen using a lens system
Since the birth of sound film, virtually all film projectors in commercial movie theaters project at a constant speed of 24 frame/s. A sound film is a motion picture with synchronized sound, or sound technologically coupled to image as opposed to a Silent film. This speed was chosen for financial and technical reasons - it was the slowest speed (and thus required the least film stock and was cheapest for producers) at which a satisfactory reproduction and amplification of sound could be conducted. There are some specialist formats (eg Showscan and Maxivision) which project at higher rates, often 48 frame/s. Showscan is a cinema process developed by Douglas Trumbull. Like some other spectacular wide-screen processes it utilizes 70 mm film but Showscan films and projects at a frame Maxivision 24 and Maxivision 48 are 35 mm motion picture film formats created by Dean Goodhill in 1999
Silent films usually were not projected at constant speeds [1] but rather were varied throughout the show at the discretion of the projectionist, often with some notes provided by the distributor. Speeds ranged from about 18 frame/s on up - sometimes even faster than modern sound film speed (24 frame/s). Contrary to received opinion, 16 frame/s - though sometimes used as a camera shooting speed - was dangerously inadvisable for projection, due to the high risk of the nitrate-base prints catching fire in the projector. Nitrocellulose (also cellulose nitrate, flash paper) is a highly flammable compound formed by Nitrating Cellulose through exposure to (A dramatic rendition of a nitrate print fire and its potentially devastating effects is famously found in Nuovo Cinema Paradiso, which revolves around the goings-on of a projectionist. Nuovo Cinema Paradiso ( 1988) an Italian Film written and directed by Giuseppe Tornatore. )
Principles of operation
Projection elements
As in a slide projector there are essential optical elements:
Light source
An incandescent lamp or an electric arc light produces light. A slide projector is an opto-mechanical device to view photographic slides. The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric Light that works by Incandescence, (a general The traditional carbon arc or modern xenon arc light source produces sufficient heat to burn the film should the film remain stationary for more than a fraction of a second. A xenon arc lamp is an artificial light source Powered by Electricity, it uses Ionized Xenon gas to produce a bright white light that closely Xenons were introduced in the 1950s and are now the more common source, being easier and safer to maintain for the most part.
Reflector and condenser lens
A curved reflector redirects light that would otherwise be wasted toward the condensing lens.
A positive curvature lens concentrates the reflected and direct light toward the film gate. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging
Douser
(Also spelled dowser. )
A metal blade which cuts off light before it can get to the film - usually this is part of the lamphouse, and may be manually or automatically operated. Some projectors have a second, electrically-controlled douser that is used for changeovers (sometimes called a "changeover douser" or "changeover shutter"). Some projectors have a third, mechanically-controlled douser that automatically closes when the projector slows down (called a "fire shutter" or "fire douser"), to protect the film if a failsafe causes the motor to shutdown. Dousers protect the film when the lamp is on but the film is not moving, preventing the film from melting from prolonged exposure to the direct heat of the lamp. It also prevents the lens from scarring or cracking from excessive heat.
Film gate and single image
A single image of the series of images comprising the movie is positioned and held flat within an aperture called the gate. The gate also provides a slight amount of friction so that the film does not advance or retreat except when driven to advance the film to the next image.
Shutter
A commonly-held misconception is that film projection is simply a series of individual frames dragged very quickly past the projector's intense light source; this is not the case. If a roll of film were merely passed between the light source and the lens of the projector, all that would be visible on screen would be a continuous blurred series of images sliding from one edge to the other. It is the shutter that gives the illusion of one full frame being replaced exactly on top of another full frame. A rotating petal or gated cylindrical shutter interrupts the emitted light during the time the film is advanced to the next frame. The viewer does not see the transition, thus tricking the brain into believing a moving image is on screen. Modern shutters are designed with a flicker-rate of two times (48 Hz) or even sometimes three times (72 Hz) the frame rate of the film, so as to reduce the perception of screen flickering. (See Frame rate and Flicker fusion threshold. Frame rate, or frame frequency, is the measurement of the Frequency (rate at which an imaging device produces unique consecutive images called frames The The flicker fusion threshold (or flicker fusion rate) is a concept in the Psychophysics of vision. ) Higher rate shutters are less light efficient, requiring more powerful light sources for the same light on screen.
Outer sprockets rotate continuously while the frame advance sprockets are controlled by the mechanism shown.
Imaging lens and aperture plate
A lens system with multiple optical elements directs the image of the film to a viewing screen. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging Different lenses are used for different aspect ratios. Each of these lenses comes with an aperture plate, a piece of metal with a precisely cut rectangular hole in the middle of equivalent aspect ratio. The aperture plate is placed just behind the gate, and masks off any light from hitting the image outside of the area intended to be shown (most modern films have extra image on the frame that is meant to be masked off in the projector).
Viewing screen
In most cases this is a reflective surface which may be either aluminized (for high contrast in moderate ambient light) or a white surface with small glass beads (for high brilliance under dark conditions). Projection screens are installations consisting of blank surface and a support structure used for displaying a projected Image for the view of an audience In a commercial theater, the screen also has hundreds of small, evenly spaced holes in order to allow the passage of sound from the speakers and subwoofer which often are directly behind it.
Film transport elements
Film supply and takeup
Two reel system
The two reel system is also known as a changeover system, after the switching mechanism that operates between the end of one reel and the beginning of the next. In a two reel system the feed reel has a slight drag to maintain tensioning in the film, while the takeup reel is driven with a constant tension by a mechanism that is allowed to slip.
The two reel system was almost universally used before the advent of the single reel system for movie theaters in order to be able to show feature-length films. Although one reel long-play systems tend to be more popular with the newer multiplexes, the two reel system is still in significant use to this day. The projector operator operates two projectors, threading one with the next reel while the other projector plays the current reel. As the outgoing reel approaches its end, the projectionist looks for cue marks, at the upper right corner of the picture. A cue mark, also known as a cue dot, a changeover cue or simply a cue is a visual indicator used with motion picture film prints usually placed Usually these are dots or circles, although they can also be slashes. (Some older films have occasionally been known to have used squares or triangles, and even positioned the cues in the middle of the right edge of the picture. ) The first cue appears twelve feet (3. 7 m) or eight seconds at 24 frame/s before the end of the reel, and signals the projectionist to start the motor of the projector containing the incoming reel. After another ten and a half feet (3. 2 m) or seven seconds at 24 frame/s, the changeover cue should appear, which signals the projectionist to actually make the changeover. When this second cue appears, the projectionist has one and a half feet (457 mm) or one second at 24 frame/s to make the changeover - if it doesn't occur within one second, the tail leader of the outgoing reel will be projected on the screen. On some projectors, the operator would be alerted to the change by a bell that operated when the feed reel rotation exceeded a certain speed (that reel rotates faster as the film is exhausted), or based on the diameter of the remaining film (Premier Changeover Indicator Pat. 411992), although many projectors do not have such an auditory system.
During the actual operation of a changeover, the two projectors use an interconnected electrical control connected to the changeover button so that as soon as the button is pressed, the changeover douser on the outgoing projector is closed in sync with the changeover douser on the incoming projector. If done properly, a changeover should be virtually unnoticeable to an audience. In older theaters, there may be manually operated, sliding covers in front of the projection booth's windows. A changeover with this system is often clearly visible as a wipe on the screen. In Film editing, a wipe is a gradual spatial transition from one image to another
The size of the reels can vary based on the projectors, but generally films are divided and distributed in reels of up to 2000 feet (610 m, about 22 minutes at 24 frame/s). Some projectors can even accommodate up to 6000 feet (1,830 m), which minimizes the number of changeovers in a showing. Certain countries also divide their film reels up differently; Russian films, for example, often come on 1000 foot (305 m) reels, although it's likely that most projectionists working with changeovers would combine them into longer reels of at least 2000 feet (610 m), to minimize changeovers and also give sufficient time for threading and any possibly needed troubleshooting time.
Single reel system
There are two largely used single reel systems (also known as long-play systems) today: the tower system (vertical feed and takeup) and the platter system (non-rewinding; horizontal feed and takeup).
The tower system largely resembles the two reel system, except in that the tower itself is generally a separate piece of equipment used with a slightly modified standard projector. The feed and takeup reels are held vertically on the axis, except behind the projector, on oversized spools with 12,000 foot (3,660 m) capacity or about 133 minutes at 24 frame/s. This large capacity alleviates the need for a changeover on an average-length feature; all of the reels are spliced together into one giant one. The tower is designed with four spools, two on each side, each with its own motor. This allows the whole spool to be immediately rewound after a showing; the extra two spools on the other side allow for a film to be shown while another is being rewound or even made up directly onto the tower. Each spool requires its own motor in order to set proper tensioning for the film, since it has to travel (relatively) much further between the projector film transport and the spools. As each spool gains or loses film, the tension must be periodically checked and adjusted so that the film can be transported on and off the spools without either sagging or snapping.
In a platter system the individual 20-minute reels of film are also spliced together as one large reel, but the film is then wound onto a horizontal rotating table called a platter. Three or more platters are stacked together to create a platter system. Most of the platters in a platter system will be occupied by film prints; whichever platter happens to be empty serves as the "take-up reel" to receive the film that is playing from another platter.
The way the film is fed from the platter to the projector is not unlike an eight-track audio cartridge. This is an article about the 8-track cartridge For eight-track multitracking see Multitrack recording. Film is unwound from the center of the platter through a mechanism called a payout unit which controls the speed of the platter's rotation so that it matches the speed of the film as it is fed to the projector. The film winds through a series of rollers from the platter stack to the projector, through the projector, through another series of rollers back to the platter stack, and then onto the platter serving as the take-up reel.
This system makes it possible to project a film multiple times without needing to rewind it. As the projectionist threads the projector for each showing, he transfers the payout unit from the empty platter to the full platter and the film then plays back onto the platter it came from. In the case of a double feature, each film plays from a full platter onto an empty platter, swapping positions on the platter stack throughout the day.
The advantage of a platter is that the film need not be rewound after each show, which can save labor. Rewinding risks rubbing the film against itself, which can cause scratching of the film and smearing of the emulsion which carries the pictures. The disadvantages of the platter system are that the film can acquire diagonal scratches on it if proper care is not taken while threading film from platter to projector, and the film has more opportunity to collect dust and dirt as long lengths of film are exposed to the air. A clean projection booth kept at the proper humidity is of great importance, as are cleaning devices that can remove dirt from the film print as it plays.
Automation and the rise of the multiplex
The single reel system can allow for the complete automation of the projection booth operations, given the proper auxiliary equipment. Automation ( Ancient Greek: = self dictated) roboticization or industrial automation or Numerical control is the use of Control systems Since films are still transported in multiple reels they must be joined together when placed on the projector reel and taken apart when the film is to be returned to the distributor. It is the complete automation of projection that has enabled the modern "multiplex" cinema - a single site typically containing from 8 to 24 theaters with only a few projection and sound technicians, rather than a platoon of projectionists. Cinemaaustraliajpg|thumb|A movie theater in Australia ]]A movie theater, movie theatre, picture theatre or cinema is a venue The multiplex also offers a great amount of flexibility to a theater operator, enabling theaters to exhibit the same popular production in more than one auditorium with staggered starting times. It is also possible, with the proper equipment installed, to "interlock", i. e. thread a single length of film through multiple projectors. This is very useful when dealing with the mass crowds that an extremely popular film may generate in the first few days of showing, as it allows for a single print to serve more patrons.
Feed and extraction sprockets
Smooth wheels with triangular pins called sprockets engage perforations punched into one or both edges of the film stock. A sprocket is a profiled Wheel with teeth that meshes with a chain, track or other perforated or indented material These serve to set the pace of film movement through the projector and any associated sound playback system.
Film loop
As with motion picture cameras, the intermittent motion of the gate requires that there be loops above and below the gate in order to serve as a buffer between the constant speed enforced by the sprockets above and below the gate and the intermittent motion enforced at the gate. Some projectors also have a sensitive trip pin above the gate to guard against the upper loop becoming too big. If the loop hits the pin, it will close the dousers and stop the motor to prevent an excessively large loop from jamming the projector.
Film gate pressure plate
A spring loaded pressure plate functions to align the film in a consistent image plane, both flat and perpendicular to the optical axis. It also provides sufficient drag to prevent film motion during the frame display, while still allowing free motion under control of the intermittent mechanism. The plate also has spring-loaded runners to help hold film while in place and advance it during motion.
Intermittent mechanism
The intermittent mechanism can be constructed in different ways. The intermittent mechanism or intermittent movement is the device by which Film is regularly advanced and then held in place for a brief duration of time in a For smaller gauge projectors (8 mm and 16 mm), a pawl mechanism engages the film's sprocket hole one side, or holes on each side. This pawl advances only when the film is to be moved to the next image. As the pawl retreats for the next cycle it is drawn back and does not engage the film. This is similar to the claw mechanism in a motion picture camera.
In 35 mm and 70 mm projectors, there usually is a special sprocket immediately underneath the pressure plate known as the intermittent sprocket. Unlike all the other sprockets in the projector, which run continuously, the intermittent sprocket operates in tandem with the shutter, and only moves while the shutter is blocking the lamp, so that the motion of the film cannot be seen. It also moves in a discrete amount at a time, equal to the number of perforations that make up a frame (4 for 35 mm, 5 for 70 mm). The intermittent movement in these projectors is usually provided by a Maltese Cross mechanism (also known as the Geneva Mechanism). The Geneva drive or Maltese cross is a mechanism that translates a continuous Rotation into an intermittent rotary motion
IMAX projectors use what is known as the rolling loop method, in which each frame is sucked into the gate by a vacuum, and positioned by registration pins in the perforations corresponding to that frame.
Types of projectors
Projectors are classified by the size of the film used, i. e. the film format. A film format is a technical definition of a set of standard characteristics regarding image capture on Photographic film, for either stills or movies Typical film sizes:
8 mm
Long used for home movies before the video camera, this uses double sprocketed 16 mm film, which is run through the camera twice. 8 mm film is a motion picture film format in which the filmstrip is eight Millimeters wide The 16 mm film is then split lengthwise into two 8 mm pieces that are spliced to make a single projectable film with sprockets on one side.
Super 8
Developed by Kodak, this film stock uses very small sprocket holes close to the edge that allow more of the film stock to be used for the images. Super 8 mm film, also simply called Super 8, is a motion picture film format released in 1965 by Eastman Kodak as an improvement of the Eastman Kodak Company ( is an American multinational Public company which produces imaging and photographic materials and equipment This increases the quality of the image. The film is premade in the 8 mm width, not split during processing as is the earlier 8 mm. Magnetic stripes could be added to carry encoded sound to be added after film development.
9. 5 mm
Film format introduced by Pathé Frères in 1922 as part of the Pathé Baby amateur film system. 95 mm film is an amateur Film format introduced by Pathé Frères in 1922 as part of the Pathé Baby amateur film system It was conceived initially as an inexpensive format to provide copies of commercially-made films to home users. The format uses a single, central perforation (sprocket hole) between each pair of frames, as opposed to 8 mm film which has perforations along one edge, and most other film formats which have perforations on each side of the image. It became very popular in Europe over the next few decades and is still used by a small number of enthusiasts today. Over 300,000 projectors were produced and sold mainly in France and England, and many commercial features were available in the format. In the sixties the last projectors of this format were being produced. They are now collectors' items.
16 mm
This was a popular format for audio-visual use in schools and as a high-end home entertainment system before the advent of broadcast television.
35 mm
The most common film size for theatrical productions during the 20th century. 35 mm film is the basic Film gauge most commonly used for both still Photography and Motion pictures, and remains relatively unchanged since its In fact, the common 35 mm camera, developed by Leica, was designed to use this film stock and was originally intended to be used for test shots by movie directors and cinematographers. Leica Camera AG is a leading German optical company that has been designing and developing Cameras since 1913 and manufacturing them in series production since
35 mm film is typically run vertically through the camera and projector. VistaVision is a variant of the 35 mm motion picture film format created by Paramount Pictures in 1954 based on the Glamorama and Superama In the mid 1950's the VistaVision[1] system presented wide screen movies in which the film moved horizontally, allowing much more film to be used for the image as this avoided the anamorphic reduction of the image to fit the frame width. VistaVision is a variant of the 35 mm motion picture film format created by Paramount Pictures in 1954 based on the Glamorama and Superama As this required specific projectors it was largely unsuccessful as a presentation method while remaining attractive as filming, intermediate, and source for production printing and as an intermediate step in special effects to avoid film granularity, although the latter is now supplanted by digital methods.
70 mm
High end movie productions were often produced in this film gauge in the 1950s and 1960s and many very large screen theaters are still capable of projecting it in the 21st century. 70 mm film (or 65 mm film) is a wide high-resolution film gauge of superior quality to standard 35 mm motion picture film format. It is often referred to as 65/70, as the camera uses film 65 mm wide, but the projection prints are 70 mm wide. The extra five millimeters of film accommodated the soundtrack, usually a six track magnetic stripe. The most common theater installation would use dual gauge 35/70mm projectors.
70 mm film is also used in both the flat and domed IMAX projection system. IMAX (short for Image MAXimum is a Film format created by Canada 's IMAX Corporation that has the capacity to display images of far greater size and In IMAX the film is transported horizontally in the film gate, similar to VistaVision. VistaVision is a variant of the 35 mm motion picture film format created by Paramount Pictures in 1954 based on the Glamorama and Superama Some productions intended for 35 mm anamorphic release were also released using 70 mm film stock. A 70 mm print made from a 35 mm negative is significantly better in appearance than an all 35 mm process, and allowed for a release with 6 track magnetic audio.
The advent of 35 mm prints with digital soundtracks in the 1990s largely supplanted the widespread release of the more expensive 70 mm prints.
Sound
Regardless of the sound format, any sound represented on the film image itself will not be the sound for the particular frame it occupies. All optical sound formats must be offset from the image because the image is projected with intermittent motion. If the sound head on the projector was adjacent to the gate, the sound would be a jerky start-stop-start-stop and so on. Therefore the sound head requires continuous motion and will be located a certain number of frames before or after the gate.
- See the 35 mm film article for more information on both digital and analog methods. 35 mm film is the basic Film gauge most commonly used for both still Photography and Motion pictures, and remains relatively unchanged since its
Optical
With 16 mm and the larger sizes it is practical to add a narrow channel of optically encoded sound track. This is read using an illuminating light or laser and a photocell or photodiode. Photosensors or photodetectors are Sensors of Light or other Electromagnetic energy A photodiode is a type of Photodetector capable of converting Light into either current or Voltage, depending upon the mode of operation In 16 mm, this is a single mono track, and the sound head is 26 frames after the gate. In 35 mm, this can be mono or stereo, the latter including several different Dolby noise reduction systems (including Dolby A and Dolby SR). Dolby NR is the name given to a series of noise reduction systems developed by Dolby Laboratories for use in analogue Magnetic tape recording The Dolby SR noise reduction format ( Spectral Recording) was developed by Dolby Laboratories and has been in common use in professional audio since 1986 The sound head is located twenty frames after the gate for 35 mm projectors. Originally optical sound was variable density, where the transparency/opacity level of the sound track was used to represent sound. This had disadvantages because the grain of the film caused a background hiss, and so was replaced with the now-universal standard variable area. In this system, a clear waveform on black background represents the sound, and the width of the waveform is equivalent to the amplitude. Variable area does have slightly less frequency response than variable density. In the 1970s and early 1980s, optical sound Super-8 mm copies were produced mainly for airline in-flight movies. This technology was soon made obsolete by video equipment.
Digital
Modern theatrical systems use optical representations of digitally encoded multi-channel sound. An advantage of digital systems is that the offset between the sound and picture heads can be varied and then set with the digital processors. Digital sound heads are usually above the gate. All digital sound systems currently in use have the ability to instantly and gracefully fall back to the optical sound system should the digital data be corrupt or the whole system fail.
Cinema Digital Sound (CDS)
Created by Kodak and ORC (Optical Radiation Corporation), Cinema Digital Sound was the first attempt to bring multi-channel digital sound to first-run theaters. CDS was available on both 35 mm and 70 mm films. Film prints equipped with CDS did not have the conventional analog optical or magnetic soundtracks to serve as a "back-up" in case the digital sound was unreadable. Another disadvantage of not having an analog back-up track is that CDS required extra film prints be made for the theaters equipped to play CDS. The three formats that followed, Dolby Digital, DTS and SDDS, can co-exist with each other and the analog optical soundtrack on a single version of the film print. This means that a film print carrying all three of these formats (and the analog optical format, usually Dolby SR) can be played in whichever format the theater is equipped to handle. CDS did not achieve wide-spread use and ultimately failed. It premiered with the film Dick Tracy and was used with several other films, such as Days of Thunder and Terminator 2: Judgement Day.
Sony Dynamic Digital Sound (SDDS)
SDDS sound runs on the outside of 35 mm film, between the perforations and the edges, on both edges of the film. SDDS stands for Sony Dynamic Digital Sound which is a cinema Sound system developed by Sony SDDS was the first digital system that could handle up to eight channels of sound. The additional two tracks are for an extra pair of screen channels (Left Center and Right Center) located between the 3 regular screen channels (Left, Center and Right). A pair of CCDs located in a unit above the projector read the two SDDS tracks. A charge-coupled device ( CCD) is an analog Shift register, that enables the transportation of analog signals (electric charges through successive stages (capacitors The information is decoded and decompressed before being passed along to the cinema sound processor. By default, SDDS units use an onboard Sony Cinema Sound Processor, and when the system is set up in this manner, the theatre's entire sound system can be equalized in the digital domain. In contrast, both DTS and Dolby Digital soundtracks must be passed through to standard analog cinema sound processors - which are also used for analog optical sound, so equalization of the sound remains in the analog domain. The audio data in an SDDS track is compressed in the 20-bit ATRAC2 compression scheme at a ratio of about 4. 5:1. SDDS premiered with the film Last Action Hero. Last Action Hero is a 1993 action comedy Film directed by John McTiernan. Sony ceased the sale of SDDS processors in 2001-2002.
Dolby Digital
Also known as Spectral Recording Digital or "SR•D. Dolby Digital is the marketing name for a series of lossy audio compression technologies developed by Dolby " Sound is printed between the perforations and is 26 frames before the picture (the offset can be varied based on processing presets). Dolby Digital produces 6 discrete channels. In a variant called SR•D EX, the left and right surround channels can be dematrixed into left, right, and back surround, using Dolby Pro Logic. Dolby Pro Logic is a Surround sound processing technology designed to decode soundtracks encoded with Dolby Surround. The audio data in a Dolby Digital track is compressed in the 16-bit AC-3 compression scheme at a ratio of about 12:1. The images between each perforation are read by a CCD located either above the projector or in the regular analog sound head below the film gate. A charge-coupled device ( CCD) is an analog Shift register, that enables the transportation of analog signals (electric charges through successive stages (capacitors The information is then decoded, decompressed, and converted to analog; this can happen either in a separate SR-D processor that feeds signals to the cinema sound processor, or SR-D decoding can be built-in to the cinema processor.
As of 2006, Dolby has discontinued sale of their external SR-D processor (the DA20), so, aside from the used market, purchasing a Dolby processor with integrated SR-D is the only way to purchase an SR-D decoder.
A consumer version of Dolby Digital is also used on most DVDs, often at higher data rates than the original film. DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is Dolby Digital officially premiered with the film Batman Returns, but it was earlier tested at some screenings of Star Trek: The Undiscovered Country. Batman Returns is a 1992 Superhero film directed by Tim Burton. Star Trek VI The Undiscovered Country is the sixth feature film based on the Star Trek Science fiction Television series.
Digital Theater Systems (DTS)
DTS actually stores the sound information on separate CD-ROMs supplied with the film. DTS (also known as Digital Theater Systems) owned by DTS Inc ( is a multi-channel digital Surround sound format used for both commercial/theatrical The CDs are fed into a special modified computer which syncs up with the film through the use of DTS time code, decompresses the sound, and passes it through to a standard cinema processor. The time code is placed between the optical sound tracks and the actual picture, and is read by an optical LED ahead of the gate. The time code is actually the only sound system which is not offset within the film from the picture, but still needs to be physically set offset ahead of the gate in order to maintain continuous motion. Each disc can hold slightly over 90 minutes of sound, so longer films will require a second disc. Three types of DTS sound exist: DTS-ES (Extended Surround), an 8 channel digital system; DTS-6, a 6 track digital system, and a now obsolete 4 channel system. DTS-ES derives a back surround channel from the left surround and right surround channels using Dolby Pro Logic. Dolby Pro Logic is a Surround sound processing technology designed to decode soundtracks encoded with Dolby Surround. The audio data in a DTS track is compressed in the 20-bit APTX-100 compression scheme at a ratio of about 4. 5:1. Of the three digital formats currently in use, DTS is the only one that has been used with 70 mm presentations. DTS was premiered on Jurassic Park. Jurassic Park is a 1993 Science fiction film directed by Steven Spielberg and based on the novel of the same name by Michael A consumer version of DTS is available on some DVDs. DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is
Magnetic sound
70 mm, which had no optical sound, used the 5 millimeters gained between the 65 mm negative and the final release print to place three magnetic tracks on each side of the perforations, for a total of six tracks. Unlike all other non-double head magnetic sound, 70 mm magnetic heads are located before the gate. Until the introduction of digital sound, it was fairly common for 35 mm films to be blown up to 70 mm often just to take advantage of the greater number of sound tracks. 35 mm four-track magnetic sound was used from the 1950s through the mid 1970s for big-budget feature prints. It was of excellent quality, although somewhat prone to damage and erasure over time. As analog optical stereo gained popularity (it was also more durable and far less expensive to include on a film print), 35 mm four-track magnetic sound was increasingly only used for special road show screenings, and the development of digital sound systems made it completely obsolete.
35 mm and 16 mm each are sometimes run in sync with a separate reel of magnetic sound (known as double head projection because two reels are running on one projector in sync); the image goes through a gate while the magnetic reel passes over a sound head. Since the sound is on a separate reel, it does not need to be offset from the image. This system is usually used only for very low-budget or student productions, or for screening rough cuts of films before the creation of a final married print. Sync between the two reels is checked with SMPTE leader, also known as countdown leader. A film leader is a length of film attached to the head or tail of a film to assist in threading a Projector or Telecine. If the two reels are synced, there should be one frame of "beep" sound exactly on the "2" frame of the countdown - 2 seconds or 48 frames before the picture start.
On certain stocks of Super 8 and 16 mm an iron-oxide sound recording strip was added for the direct synchronous recording of sound which could then be played by projectors with a magnetic sound head. It has since been discontinued by Kodak on both gauges.
Leaders
Academy leader is placed at the head of release prints containing information for the projectionist and featuring numbers which are black on a clear background, counting from 11 to 3 at 16 frame intervals (16 frames in 35 mm film = 1 ft). At -12 feet there is a START frame.
SMPTE leader is placed at the head of release prints or video masters containing information for the projectionist or video playback tech. The numbers count down in seconds from 8 to 2 at 24 frame intervals ending at the first frame of the "2" followed by 47 frames of black.
Usually there's an audio POP that play 48 frames (2 seconds at 24 frame per second) before first frame of action (FFOA) that helps to sync audio and video during printing processes or postproduction. Remember that audio analog optical sound is printed 20 frames before image, because sound head is big and should stay far from the projection frame. French people before april 2007 print audio 21 frame before, instead of 20.
Types of lenses and screens
Orthographic
Before the advent of certain wide screen technologies, lenses always reproduced the exact proportions of the film image onto the screen. Such lenses are relatively simple to design and manufacture. Prior to modern wide screen, the industry standard image ratio of width to height was 1. 37:1.
35 mm VistaVision was a wide screen orthographic system. VistaVision is a variant of the 35 mm motion picture film format created by Paramount Pictures in 1954 based on the Glamorama and Superama The wide image was obtained by running the film horizontally across the gate so that the width limitation of the film was transformed to a height limitation. See the VistaVision article for more information. VistaVision is a variant of the 35 mm motion picture film format created by Paramount Pictures in 1954 based on the Glamorama and Superama
Anamorphic
The 1950's saw the development of wide screen films using special lenses for filming and projection. A widescreen image is a film computer or television image with a wider and shorter aspect ratio than the standard Academy frame developed during the Classical The images on these films retained the same proportions as in the earlier films (a 1. 37:1 width to height ratio). The wide image is compressed onto the film in the camera using additional cylindrical elements within the lens, with a corresponding lens used in the projector to expand the image to the wide screen. This technique is called anamorphic projection and various implementations have been marketed under several brand names, including CinemaScope, Panavision and Superscope, with Technirama implementing a slightly different anamorphic technique using vertical expansion to the film rather than horizontal compression. Anamorphic format is a term that can be used either for the Cinematography technique of capturing a Widescreen picture on standard 35 mm film, or other CinemaScope was a Widescreen movie format used from 1953 to 1967 Panavision is a Motion picture equipment company specializing in Cameras and lenses, based in Woodland Hills California. Of the anamorphic methods, arguably the best image was produced by the Todd-AO (for Michael Todd and American Optical) using 70 mm film and a large, curved screen. Michael Todd can refer to Mike Todd (1909&ndash1958 American film producer Mike Todd Jr The 1956 version of Around the World in Eighty Days starring David Niven and Cantinflas was the leading general release production using this process. James David Graham Niven (1 March 1910 – 29 July 1983 was an English Academy Award -winning Actor probably best known for his role as the punctuality-obsessed Fortino Mario Alfonso Moreno Reyes ( August 12, 1911 &ndash April 20, 1993) was a Mexican comedian and actor Similar 70 mm processes include Super (and Ultra) Panavision and VistaVision.
Fish eye with dome
The IMAX dome projection method (called "OMNIMAX") uses 70 mm film oriented to maximize the image area and extreme wide angle lenses to obtain an almost hemispherical image. IMAX (short for Image MAXimum is a Film format created by Canada 's IMAX Corporation that has the capacity to display images of far greater size and The field of view is tilted, as is the projection hemisphere, so one may view a portion of the ground in the foreground. Owing to the great area covered by the picture it is not as bright as seen with flat screen projection, but the immersive qualities are quite convincing. While there are not many theaters capable of displaying this format there are regular productions in the fields of nature, travel, science, and history, and productions may be viewed in most U. S. large urban regions. These dome theaters are mostly located in large and prosperous science and technology museums.
Wide and deep flat screen
The IMAX flat screen system uses large format film, a wide and deep screen, and close and quite steep "stadium" seating. IMAX (short for Image MAXimum is a Film format created by Canada 's IMAX Corporation that has the capacity to display images of far greater size and The effect is to fill the visual field to a greater degree than is possible with conventional wide screen systems. Like the IMAX dome, this is found in major urban areas, but unlike the dome system it is practical to reformat existing movie releases to this method. Also, the geometry of the theater and screen are more amenable to inclusion within a newly constructed but otherwise conventional multiple theater complex than is the dome style theater.
Multiple cameras and projectors
One wide screen development during the 1950's used non-anamorphic projection, but used three side by side synchronised projectors. Called Cinerama, the images were projected onto an extremely wide, curved screen. Cinerama is the trademarked name for a Widescreen process which works by simultaneously projecting images from three synchronized 35 mm projectors onto a huge deeply-curved Some seams were said to be visible between the images but the almost complete filling of the visual field made up for this. This showed some commercial success as a limited location (only in major cities) exhibition of the technology in This is Cinerama, but the only memorable story-telling film of two made for this technology was How the West Was Won, widely seen only in its Cinemascope re-release. This is Cinerama is a 1952 film which shows how film makers could use the new technology of Cinerama to make movies more realistic by broadening the aspect How the West Was Won is a 1962 epic Western film which follows four generations of a family (starting as the Prescotts as they move ever
While neither a technical nor a commercial success, the business model survives as implemented by the documentary production, limited release locations, and long running exhibitions of IMAX dome movies. A business model is a term used for a broad range of informal and formal descriptions that are used by enterprises to represent various aspects of its business including its purpose offerings
Three-dimensional
For techniques used to display pictures with a three-dimensional appearance, see the 3-D film article for some movie history and the stereoscopy article for technical information. See also [[stereoscopy]] In film the term 3-D (or 3D) is used to describe any visual presentation system that attempts to maintain or recreate moving images Stereoscopy, stereoscopic imaging or 3-D (three-dimensional imaging is any technique capable of recording three-dimensional visual
See also
- Film format
- List of film formats
- Projector for a directory of projector types
- Projectionist
References
- ^ Nowell-Smith, Geoffrey (ed. A film format is a technical definition of a set of standard characteristics regarding image capture on Photographic film, for either stills or movies This list of Film formats catalogues formats developed for shooting or viewing Motion pictures, ranging from the Chronophotographe format from 1888 to mid-20th century A Projectionist is a person whose profession entails the operating of a Movie projector. ) The Oxford History of World Cinema, pp. 446–449. Oxford University Press: Oxford, 1996.
External links
- Collection of restored cinema projectors and lighting by Regal Group, UK.
- Film-Tech
- American Wide Screen Museum
- The story of the DP70 - The Todd-AO Projector
- A Cinerama site
- List of 3000 movie projectors and cameras
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