The following is taken verbatim from IMAX’s patent application 20090262305, “Conversion of Cinema to Super Cinema Theater,” filed Oct. 22, 2009. It gives a fascinating history of immersive cinema from the late 1800’s through today.
Motion picture exhibition has seen a number of changes since its inception in the late 19th century. Generally, the main variables in motion picture exhibition have been the dimensions of the theatre enclosure and correspondingly the number of seats therein, the size of the screen upon which images were projected and the dimensions or format of the film negative which contained the images for presentation. Although a number of film formats were considered, one format, 35 mm wide film having an image aspect ratio of 4:3 became the industry standard. Motion picture theatres gradually evolved in size from smaller theatres to larger so-called palace theatres featuring several hundred to thousands of seats, balconies, and elaborate facades. Despite the impressive and somewhat regal atmosphere these theatres continued to feature 35 mm film projected onto narrow width screen. Eventually in the late 1920s, motion picture producers and exhibitors started experimenting with larger film formats which could enhance the visual immersion of theatre patrons and live up to the size and scope of the large palace theatres.
Some of the wide gauge/wide screen processes that appeared to challenge the 35 mm film standard included Magnascope, Polyvision, Hypergonar and Fox Grandeur. Magnascope used a novel magnifying lens to enlarge a standard 35 mm frame. Polyvision used multiple 35 mm film projectors to stitch together a composite image, while Fox Grandeur replaced 35 mm film entirely with a new 70 mm wide film format. Finally Hypergonar used a novel method of anamorphically squeezing images onto a 35 mm frame during filming and then reversing the process upon projection to fill a larger projection screen.
Although technically and aesthetically successful, the proposed wide screen systems failed to replace 35 mm as a film standard in the economically depressed 1930s and were soon abandoned. Conditions had changed somewhat by the early 1950s and the motion picture industry saw a resurgence of proposals for wide gauge/wide screen systems. Foremost among the new systems were Cinerama, a multiple 35 mm projection system, Cinemascope, an anamorphic system, Vistavision a 35 mm 8 perforation format system and Todd AO, a wide gauge system using a 70 mm 5 perforation 30 frame per second format. The new formats were successful at the box office and survived for a number of years, but none was able to seriously challenge the 35 mm film standard.
A third wave of wide gauge/wide screen motion picture exhibition started in 1969, led by IMAX Corporation, which featured the use of horizontally travelling 70 mm film with a film frame of 15 perforations in width resulting in an image area about ten times that of standard 35 mm. In addition to the large film format IMAX re-conceptualized the theatre viewing space by providing significantly larger screens which extended beyond spectators fields of view, steeply raked seating area to give unobstructed viewing of said large screen, and high fidelity six channel sound to surround the audience. The net result of these advances was a theatre experience in which audience members were immersed in image and sound as never before. IMAX theatres were successful in the institutional and exhibit marketplace. Other competing large format systems include Showscan’s 70 mm 5 perforation film projected at 60 frames per second (versus the standard 24 fps) and Iwerk’s 70 mm 5, 8 and 15 perforation film systems.
In most cases IMAX systems were installed in custom designed motion picture theatres having a large volume to house both the large screen and a steeply raked seating deck. Occasionally IMAX projection systems were placed in large hall converted stage theatres. IMAX screens could be placed in front of the stages in such theatrical structures without building structure modifications because of the large existing clear height. In some cases, such as at the Museum of Natural History in New York City, a retractable IMAX screen was placed in front of the stage that had an existing 35 mm screen at the back of the stage. Some seats at the side of the theatre near the position of the IMAX screen were removed because the visual quality at those locations was poor. The slope of the seating areas in these theatrical theatres is typically shallow, and financial constraints prevented conversion to a more desirable steeper slope. As a result, the viewing conditions in such converted theatres were not optimized for viewing IMAX motion pictures.
Grand theatres of the type frequented in the 1920s thru 1950s were sometimes converted to house the emerging wide gauge/widescreen systems of the 1950s. Conversion consisted of changing the width and curvature of the screen to match the new wider picture aspect ratio and removing a relatively high percentage of seats that no longer had viable viewing conditions. Screen centres were basically positioned at the original screen centre position at the rear wall of the theatre, and the rake of seats in the theatres was not a consideration in the conversion process.
Another type of theatre conversion addresses the desire to present motion pictures in either of two common aspect ratio formats, which are 1:85:1 and 2.35:1. The conversion process involves adjusting the curtain masking around the screen to suit the format of presentation as well as changing the lens and aperture plate. The position of the screen itself does not change.
A major trend in the motion picture industry starting in the 1970s was to group a number of small 35 mm film theatres into one large complex, or so-called multiplex theatre. These theatres, although profitable, did not provide patrons with a quality viewing experience. Over time movie attendance declined partly because of new home entertainment technologies such as cable TV, video cassette recorders, and home movie rentals. In the 1990s the motion picture exhibition industry responded to declining movie attendance by building new theatres offering stadium seating–placing each row of seats on its own tier–to improve the sight lines and thus the viewing experience of patrons. This industry advance has been very successful in improving movie attendance and is now an expected feature for theatre patrons; conventional low slope seating decks are seen as “old” and inferior. (LA Business Journal). The new stadium seat theatres, while an improvement over traditional multiplex theatres, still rely on standard 35 mm film projectors and do not provide patrons with a wide field of view or highly immersive experience.
It should be noted that in the later half of the 1990s the use of digital projectors began in a few multiplex cinemas. This trend in time will increase as digital projection systems get better in quality and higher in image resolution.
Another aspect of the conversion is to improve the quality of the audio portion of the immersive experience in a multiplex type theatre. Sound systems for cinema have evolved over the decades and the trend continues as an ongoing effort to attract the paying viewer. The surround sound systems used in today’s Multiplex theatres can provide a degree of “ambience” in the audio experience but these systems still lack the ability to create realistic immersive audio.
From the time “talkies” were introduced, motion picture cinemas had “monaural” sound systems, having only one loudspeaker located behind the center of the screen. The sound experience in such a cinema was very one dimensional and flat, with no ability to simulate sounds coming from directions other than the center of the picture. In order to improve the audio experience, cinema designers and equipment suppliers experimented with a variety of multiple loudspeaker (“multi-channel”) schemes designed to immerse the audience in a sound field which could add to the “suspension of disbelief” desired by filmmakers. One of the earliest attempts at multi-channel sound was the premier of Walt Disney’s “Fantasia” in 1939. Disney experimented with a number of sound system loudspeaker configurations as outlined in an article by William E. Garity and John N. A. Hawkins published in the August 1941 issue of the journal of the SMPTE. The last two versions of the Fantasound system, known as Mark IX and X, used 5 loudspeakers and sound from 3 separate tracks. The loudspeakers were positioned such that 3 were behind the screen (i.e. left, center, and right) and one loudspeaker was in each rear corner. The two sets of rear corner loudspeakers were switched in to supplement or replace the corresponding left and right front loudspeakers at select times during the picture presentation. Unfortunately, the war and economics cut short Disney’s sound system experiments. In the early 1950’s, Cinerama brought multi-channel sound to the forefront again with 5 to 7 loudspeaker channels located around the audience.
During the 1950’s there were several theatres equipped for the playback of multi-channel sound, of which there were primarily two formats both using magnetic stripes printed on the film. The CinemaScope 35 mm film format provided four discrete channels, consisting of 3 loudspeakers behind the screen and a monaural surround channel provided by several small loudspeakers located on the side and rear walls of the cinema. These surround loudspeakers provided a degree of “ambience” to the sound experience in combination with the directional sound produced by the 3 screen loudspeakers, and thus added to the immersive effects presented to the audience. The Todd-AO 70 mm film format added two additional loudspeakers behind the screen, Left Center and Right Center, between the center loudspeaker and the left and right speakers.
In the 1970’s, Dolby pioneered several advances in cinema sound, including extended low-frequency sound (sub-bass), noise reduction, and Stereo Optical sound. Dolby Stereo Optical provided 4 channels of sound (left, center, right, and mono surround) using an encoding technique to store the analog soundtrack on two analog optically printed stripes on the film. This became the standard for normal cinemas, and remains in use today in non-digital cinemas.
In 1979, Dolby added to the immersive effects of cinema sound by developing stereo surrounds, in which the left distributed loudspeaker channel could reproduce different sounds than the right channel. But, the surround effects were still effectively ambience sounds, and were unable to reproduce directionality with any precision due to the distributed configuration of the surround loudspeakers.
In the 1980’s, IMAX Corporation standardized on a 6-channel sound system with a discrete surround sound configuration and a separate sub-bass channel for IMAX Theatres. This type of system provides substantially better sound imaging by utilizing custom-designed loudspeakers located in each rear corner behind the audience, each powered by a separate audio channel. The immersive effects of this type system are much more impressive, and allow the filmmaker the ability to position sound more precisely–directly in front of, in front above, around, and behind the audience.
In 1987, Imax installed the first Digital Sound Reproducer in an IMAX Theatre. By 1990, uncompressed Digital Sound was available to all IMAX Theatres. Also in 1990, with the release of the movie “Dick Tracy,” CDS uncompressed digital sound on 35 mm film was introduced to the general cinema industry by a joint venture of Orcon and Kodak.
Because CDS was not compatible with standard optical sound on 35 mm film, the CDS format was discontinued soon thereafter.
Between 1992 and 1993, three systems of digital sound for cinema were released–Dolby Digital, DTS, and Sony SDDS. All three of these formats utilized some form of digital compression to reduce the storage requirements (on CD-ROM for DTS) or to allow the digital audio signal to be printed on the 35 mm film (with Dolby Digital and SDDS) without displacing the optical track as did the CDS system. While these systems use different compression techniques–some considered “better sounding” than others–IMAX Digital Sound remains the only uncompressed digital cinema sound format in general use today.
All three of the digital sound systems used in conventional 35 mm and digital cinemas make use of the same distributed side and rear surround loudspeakers to create a sense of ambience for the film soundtrack. Even though these digital systems may sound “better” than the older optical systems, sound immersion remains limited due to the inability of multiple distributed loudspeakers to provide precise directionality and image placement.
Motion picture exhibitors have expressed interest in providing additional quality improvements to mainstream motion pictures by adding a special, custom designed, smaller scale Imax theatre to their multiplexes. This has proved popular with patrons and exhibitors, but has not been widely adopted because of high costs associated with constructing the adjunct theatre.
It is desirable to be able to provide mainstream multiplex theatres with the same manner of widescreen presentation experience as large hall custom designed theatres, but at a lower, more affordable cost. There is a need to be able to economically convert an existing mainstream multiplex motion picture theatre into a widescreen theatre that is qualitatively superior in terms of projected image quality, field of view, and of a more realistic immersive audio experience that does not exist in multiplex type theatres. As a result of having overbuilt the number of multiplex theatres the economics of this situation dictates that converting existing multiplex theatres makes better sense than building additional new multiplexes with larger screen sizes.