wiki英文上面的imax介绍

IMAX (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 resolution than conventional film display systems. A standard IMAX screen is 22 m wide and 16 m high (72.6 x 52.8 ft), but can be larger. Currently, IMAX is the most widely-used system for large-format, special-venue film presentations. As of 2006, there were 280 IMAX theatres in 40 countries (60 percent of these are located in the United States and Canada). A variation of IMAX, IMAX Dome (originally called OMNIMAX), is designed for projection on tilted dome screens. Films can also be projected in 3D with IMAX 3D. Contents [hide] 1 Precursors 2 History 3 Technical aspects 4 IMAX Dome/OMNIMAX 5 IMAX 3D 6 IMAX HD 7 Viewer experience 8 Recent trouble 9 Content 10 IMAX as a music venue 11 Technical specifications 12 IMAX venues 13 External links [edit] Precursors The desire to increase the visual impact of film has a long history. In 1929, Fox introduced Fox Grandeur, the first 70 mm movie format, which quickly fell from use. In the 1950s, Cinemascope and VistaVision widened the projected image from 35 mm film, and there were multi-projector systems such as Cinerama for even wider presentations. While impressive, Cinerama was cumbersome and difficult to set up, and the joints between the screens were difficult to hide. [edit] History The IMAX system was developed by three Canadians: Graeme Ferguson, Roman Kroitor, and Robert Kerr. During Expo 67 in Montreal, Canada, In the Labyrinth, their multi-projector giant-screen system had a number of technical difficulties that led them to design a single-projector/single-camera system. Tiger Child, the first IMAX film, was demonstrated at Expo '70 in Osaka, Japan. The first permanent IMAX system was set up in Toronto at Ontario Place in 1971, and is still in operation. During Expo '74 in Spokane, Washington, a very large IMAX screen that measured 90 x 65 ft (27.3 x 19.7 m) was featured in the US Pavilion (the largest structure in the expo). About 5 million visitors viewed the screen, which covered a person's total field of vision when looking directly forward. This easily created a sensation of motion for nearly everyone, and motion sickness in a few viewers. However, it was only a temporary screen for the six-month duration of the Expo. Several years later, a standard size IMAX screen was installed, and is still in operation at the renamed "Riverfront Park IMAX Theatre." The first permanent IMAX Dome installation, the Reuben H. Fleet Space Theater and Science Center, opened in San Diego's Balboa Park in 1973. The first permanent IMAX 3D theatre was built in Vancouver, British Columbia for Transitions at Expo '86, and is still very much in use, as it is situated at the tip of Canada Place, a Vancouver landmark. As of Sep 2006, there were 280 IMAX theatres in 34 countries around the world. Half of these are commercial theatres and half are in educational venues. [edit] Technical aspects A comparison between 35 mm and 15/70 mm negative areas An IMAX camera inside a display case The 15 kW Xenon short-arc lamp used in IMAX projectorsThe intent of IMAX is to dramatically increase the resolution of the image by using much larger film stock at a resolution of about 10000 x 7000 pixels. To do this, 70 mm film stock is run "sideways" through the cameras. While traditional 70 mm film has an image area that is 48.5 mm wide and 22.1 mm tall (for Todd-AO), in IMAX the image is 69.6 mm wide and 48.5 mm tall. In order to expose at standard film speed of 24 frames per second, three times as much film needs to move through the camera each second. Drawing the large-format film through the projector was a difficult technical problem to solve; conventional 70 mm systems were not steady enough for the 586x magnification. IMAX projection involved a number of innovations. William Shaw of IMAX adapted an Australian patent for film transport called the "rolling loop" by adding a compressed-air "puffer" to accelerate the film, and put a cylindrical lens in the projector's "block" for the film to be vacuumed up against during projection (called the "field flattener" because it served to flatten the image field). Because the film actually touches the "field flattener" lens, the lens itself is twice the height of the film and is connected to a pneumatic piston so it can be moved up or down while the projector is running, this way, if a piece of dust comes off the film and sticks to the lens, the projectionist can switch to the clean side of the lens at the push of a button. The lens also has "wiper bars" made of a felt or brush-like material which can wipe the dust off the lens as it moves up or down to keep the show clean. IMAX projectors are pin-stabilized, meaning 4 registration pins engage the sprockets at the corners of the projected frame to ensure perfect alignment. Mr. Shaw added cam-controlled arms to decelerate each frame to eliminate the microscopic shaking as the frame "settled" onto the registration pins. The projector's shutter is also open for around 20% longer than in conventional equipment and the light source is brighter. The largest 12-18 kW xenon arc lamps have hollow, water-cooled electrodes. An IMAX projector is therefore a substantial piece of equipment, weighing up to 1.8 tonnes and towering at over 70" [178cm] tall and 75" [195cm] long. The xenon lamps are made of a thin layer of quartz crystal, and contain xenon gas at a pressure of about 25 atmospheres; because of this, projectionists are required to wear protective body armour when changing or handling these lamps because the flying shards of crystal could be deadly when combined with the high pressure of the gas within. IMAX uses a stronger "ESTAR" (Kodak's tradename for PET film) base. The reason is not for strength, but precision. Developing chemicals do not change the size or shape of Estar, and IMAX's pin-registration (esp. the cam mechanism) is intolerant of either sprocket-hole or film-thickness variations. The IMAX format is generically called "15/70" film, the name referring to the 15 sprockets per frame of 70 mm stock. The bulk of the film requires large platters rather than conventional film reels. IMAX film does not include an embedded soundtrack in order to use more of the image area. Instead the IMAX system specifies a separate six-channel 35 mm magnetic tape synchronized to the film. (This original system--35 mm mag tape locked to a projector--was commonly used to "dub" or insert studio sound into the mixed soundtrack of conventional films.) By the early 90's, a separate digital 6-track source was synchronized using a more precise pulse-generator as a source for a conventional SMPTE timecode synchronization system. This development presaged conventional theatrical multichannel sound systems such as Dolby Digital and DTS. This digital source came in the form of a unit called a DDP (Digital Disc Playback) in which the soundtrack was recorded onto multiple CD-ROM discs which would play the sound which was recorded to the discs as a digital audio file. This DDP system has been replaced in almost all theaters with the newer DTAC (Digital Audio Theater Control) system which utilizes a computer running the IMAX's proprietary DTAC software. The software works in a similar style as the DDP except that instead of the audio file being based on discs, it is instead played directly off a hard drive in the form of a single uncompressed audio file containing the 6 channels which are distributed directly to the amplifiers rather than using a decoding method such as Dolby Digital. IMAX theater construction also differs significantly from conventional theaters. The increased resolution allows the audience to be much closer to the screen; typically all rows are within one screen-height. (Conventional theaters seating runs 8 to 12 screen-heights) Also, the rows of seats are set at a steep angle (Up to 23 degrees in some domed theaters) so that the audience is facing the screen directly. [edit] IMAX Dome/OMNIMAX The frame layout of the IMAX Dome film. The Control room of an IMAX Dome Theatre.In the late 1960s the San Diego Hall of Science (now known as the Reuben H. Fleet Science Center) began searching North America for a large-format film system to project on the dome of their planned 76-foot tilted-dome planetarium. One of the front-running formats was a double-frame 35 mm system, until they saw IMAX. The IMAX projector was unsuitable for use inside a dome because it had a 12-foot-tall lamphouse on top. However, IMAX Corporation were quick to cooperate and were willing to redesign their system. IMAX designed an elevator to lift the projector to the center of the dome from the projection booth below. Spectra Physics designed a suitable lamphouse that took smaller lamps (about 18 inches long) and placed the bulb behind the lens instead of above the projector. Leitz of Canada developed a fisheye lens that would project the image onto a dome instead of a flat screen. The dome system, which the San Diego Hall of Science called OMNIMAX, uses a fisheye lens on the camera that squeezes a highly distorted 180 degree field of view onto the 70 mm IMAX film. The lens is aligned below the center of the frame and most of the bottom half of the circular field falls beyond the edge of the film. The part of the field that would fall below the edge of the dome is masked-off. When filming, the camera is aimed upward at an angle that matches the tilt of the dome. When projected through a matching fisheye lens onto a dome the original panoramic view is recreated. OMNIMAX wraps 180 degrees horizontally, 100 degrees above the horizon and 22 degrees below the horizon for a viewer at the center of the dome. OMNIMAX premiered in 1973 at the Reuben H. Fleet Space Theater and Science Center showing two OMNIMAX features, Voyage to the Outer Planets (produced by Graphic Films) and Garden Isle (by Roger Tilton Films) on a double bill. IMAX has since renamed the system IMAX Dome. Many theaters continue to call it OMNIMAX. OMNIMAX theaters are now in place at a number of major American museums, particularly those with a scientific focus, where the technical aspects of the system may be highlighted as part of the theme interest. The projection room is often windowed to allow public viewing and accompanied by informational placards like any exhibit. Inside the theatre, the screen may be a permanent fixture, such as at the St. Louis Science Center (which also plays a short educational video about the OMNIMAX system just before the feature film); or lowered and raised as needed, such as at the Science Museum of Minnesota (where it shares an auditorium with a standard IMAX screen). Before the feature begins, the screen is backlit to show the speakers and girders behind the screen. IMAX Dome screens may also be found at several major theme parks and Las Vegas hotels. But despite their impressive capabilities and unique experience, the system seems likely to remain a novelty rather than a widespread commercial phenomenon. Relative to their size, OMNIMAX theaters are very expensive to build and maintain, and have a relatively small seating capacity. To make matters worse, only those seats closest to the center of the theater provide the full effect of the immersive view. Museums are able to run the theaters at a profit only because they are able to subrogate the construction expenses through grants and public fundraising and then show relatively inexpensive documentary films, often while still being able to keep admission prices lower than those of standard cinemas. In this way, OMNIMAX theaters have become a "cash cow" for financially strapped public institutions. Another use of IMAX Dome technology is to provide an immersive visual experience to go with a ride simulator, as in Back to the Future: The Ride. Imax Dome was also used in the former EPCOT attraction, Horizons. [edit] IMAX 3D An IMAX 3D camera.To create the illusion of 3-dimensional depth, the IMAX 3D process uses two camera lenses to represent the left and right eyes. The two lenses are separated by an interoccular distance of about 64 mm/2.5 in., the average distance between a human's eyes. By recording on two separate rolls of film for the left and right eyes, and then projecting them simultaneously, we can be tricked into seeing a 3D image on a 2D screen. The IMAX 3D camera is very cumbersome, weighing over 113 kg/250 pounds. This makes it extremely difficult to film on-location documentaries. The IMAX screen, averaging at 8 stories tall, is the perfect medium for 3D movies to be shown on. Not only does the large negative format allow for pristine quality images, but the massive screen and close viewing distance provides a very immersive experience for the audience. There are two methods to creating the 3D illusion in the theatre. The first involves polarization. During projection, the left and right eye images are polarized perpendicular to one another as they are projected onto the IMAX screen. By wearing special eyeglasses with lenses polarized in their respective directions to match the projection, the left eye image can be viewed only by the left eye since the polarization of the left lens will cancel out that of the right eye projection, and the right eye image can be viewed only by the right eye since the polarization of the right lens will cancel out that of the left eye projection. Another method for 3D projection involves LCD shutter glasses. These glasses contain LCD panels which are synchronised to the projector which alternates rapidly at 96 frames per second between displaying the left and right images which are momentarily viewed by the appropriate eye by allowing that eye's panel to become transparent while the other remains opaque. One particular problem that 3D movies face is that the 3D effect does not extend past the boundaries of the physical screen. It is for this reason that the screen must be large enough to cover as much of the viewer's peripheral vision as possible. Another problem with IMAX 3D movies is due to an inherent difference between our eyes and the film format. Because of the large negative, depth of field is dramatically reduced, causing an often distracting depiction of the scene. Computer-generated imagery films do not have this problem as they are able to control the depth of field in the images to allow everything to be in focus. While some may argue that this is less artistic than regular 2D films that purposefully employ shallow depth of field for aesthetic reasons, the IMAX 3D experience is a much more immersive one than regular 2D films, and therefore the viewer can be disoriented by seeing images that are out of focus – a natural side-effect of the 3D experience. Improvements in the sound systems have included a 3D sound system and the elliptical-pattern speaker-clusters. [edit] IMAX HD Further improvements and variations on IMAX include the possibility of a faster 48 frames per second rate , known as IMAX HD. This system was tested in 1992 at the Canada Pavillion of the Seville Expo '92 with the film Momentum, but was deemed too costly and abandoned but not before many theaters were retrofitted to project at 48 frames, especially Canada. A theme park in Germany also used IMAX HD for their theme park ride film in the mid 1990's. [edit] Viewer experience For the viewer, these technical differences result in a much more immersive, engaging experience than conventional film projection. The large screen and close seating mean that much of the viewer's field of vision is filled with the image, and the high resolution and positional stability of the film format imparts a sense of reality and detail. IMAX film can be overwhelming at times, with some viewers experiencing motion sickness during scenes with significant motion, especially if the action cuts between moving and still scenes. In scenes where the motion on the screen moves downwards, a "free-fall" sensation is felt (like going down on a roller coaster). [edit] Recent trouble Recently, despite expanding its market with several new theaters (especially in Latin America and China), IMAX has continued to face financial difficulty. Over the summer of 2006 IMAX's stock fell markedly (by as much as 60%) with the announcement of an SEC investigation, falling again when the announced third quarter earnings were behind the previous year's. [edit] Content Although IMAX is an impressive format from a technical perspective, its popularity as a motion picture format has traditionally been limited. The expense and logistics of producing and presenting IMAX films has dictated a shorter running time compared to conventional movies for most presentations (typically around 40 minutes). The majority of films in this format tend to be documentaries ideally suited for institutional venues such as museums and science centers. IMAX cameras have been taken into space aboard the Space Shuttle, to Mount Everest, to the bottom of the Atlantic ocean, and to the Antarctic to film such documentaries. Although IMAX documentaries have been praised for their technical quality, critics have also complained that many have banal narration.[citation needed] Some IMAX theaters had shown conventional films (using conventional projection equipment) as a sideline to the native-IMAX presentations. In the late 1990s there was a wave of interest in broadening the use of IMAX as an entertainment format. A few pure-entertainment IMAX short films have been created, notably T-Rex: Back to the Cretaceous, which had a successful run in 1998 and Haunted Castle, released in 2001 (both of these were IMAX 3-D films). In 1999, Disney produced Fantasia 2000, the first full-length animated feature released exclusively in the IMAX format (the film would later have a conventional-theatrical release). Disney would also release the first 2-D live-action native IMAX entertainment film, Young Black Stallion, in late 2003. In the fall of 2002, IMAX and Universal Studios released a new IMAX-format of the 1995 theatrical film Apollo 13. This release marked the first use of the IMAX-proprietary "DMR" (Digital Re-mastering) process that allowed conventional films to be converted into IMAX format. Other theatrically-released films, would subsequently be re-released at IMAX venues using the DMR process. Because of a technical limitation on the size of the film reel, these early DMR releases were edited to conform to a two-hour length limitation. Later releases did not have this limitation. Current IMAX platters allow a run length of up to 150 minutes. It was previously reported that "Star Wars Episode III" was released with an IMAX DMR version, however it never underwent the DMR process. Venues that showed this film in an IMAX screen used standard 35mm projection. In 2003 a notable IMAX re-release, again using the DMR process, was The Matrix Reloaded. Later in 2003, the sequel The Matrix Revolutions was the first live action film to be released simultaneously in IMAX and conventional theaters, the first feature film being Treasure Planet. Reviewers have generally praised the results of the DMR blowup process, which have superior visual and auditory impact to the same films projected in 35 mm. Many large format film industry professionals point out, however, that DMR blowups are not comparable to films created directly in the 70 mm 15-perf IMAX format. They note that the decline of Cinerama coincided roughly with the supersession of the original process with a simplified, reduced-cost, technically inferior version, and view DMR with alarm. IMAX originally reserved the phrase "the IMAX experience" for true 70 mm productions, but now allows its use on DMR productions as well. However, IMAX DMR versions of commercial Hollywood films are generally popular with audiences, with many people choosing to pay more than standard admission to see the IMAX version. Since 2002 many other Hollywood films have been remastered for IMAX. Warner Brothers has especially embraced the format with the aforementioned Matrix sequels and since 2004 has been releasing its Harry Potter film franchise in IMAX to strong financial success. In 2005 WB also released Batman Begins simultaneously in IMAX, which buoyed the film's strong legs helping it reach $200m at the domestic box office, and before the fourth Harry Potter film was released in IMAX format in November had claimed the record for most box office by a DMR movie. In summer 2006 WB released the highly anticipated Superman Returns remastered for IMAX and partially digitally transformed into 3D (director Bryan Singer chose four action scenes in the film to show in 3D. The film was a disappointment at the box office in light of its huge budget and perceived large fanbase, but the IMAX 3D release helped it to have strong staying power throughout the summer movie season. Most recently, WB released the animated film Happy Feet simultaneously in both conventional theatres and in IMAX 2D format. The studio has hinted that a future IMAX 3D release was still a possibility.[1] Noted feature film director James Cameron filmed a movie about the Titanic in 3D IMAX format, Ghosts of the Abyss. Up to 2002, eight IMAX format films have received Academy Awards nomination with one win, the animated short, The Old Man and the Sea in 2000. Many IMAX films have been remastered into HDTV format for the INHD channels. [edit] IMAX as a music venue In July 2005 the BFI IMAX Cinema in London became the first to host live music concerts. IMAX theater owners increasingly look to use the venue at varying times for alternatives to films. Recently the London England IMAX has hosted a computer game festival using digital projectors on the large IMAX screen. Irish Rock band U2 is planning an IMAX 3D movie to be released sometime in 2007. It was filmed in Buenos Aires, Argentina. These uses have no particular relevance to IMAX as a product or a company. [edit] Technical specifications IMAX (15/70) spherical lenses 70mm film, 15 perforations per frame horizontal pulldown, from right to left (viewed from base side) 24 frames per second camera aperture: 70.41 mm (2.772″) by 52.63 mm (2.072″) projection aperture: at least 20.3 mm (0.80″) less than camera aperture on the vertical axis and at least 0.016″ less on the horizontal axis aspect ratio: 1.43:1 IMAX Dome/OMNIMAX Same as IMAX except: special fisheye lenses lens optically centered 9.4 mm (0.37″) above film horizontal center line projected elliptically on a dome screen, 20 degrees below and 110 degrees above perfectly centered viewers [edit] IMAX venues The Luxor IMAX Theater in the Luxor Hotel is the big black shape.Main article: List of IMAX venues Notable IMAX venues include: The Cinesphere at Ontario Place in Toronto, Ontario, Canada – the first permanent IMAX theatre. The IMAX Theatre at Canada Place in Vancouver, British Columbia, Canada – the first permanent IMAX 3D theatre. The IMAX/IMAX Dome at the Canadian Museum of Civilization in Gatineau, Quebec, Canada – the first dual IMAX/IMAX Dome installation. Futuroscope, France – theme park, only place containing all versions of IMAX theatres. (Normal, Dome, 3D, 3D Dome ("Solido") and IMAX Magic Carpet.) The Reuben H. Fleet Science Center in San Diego, California, USA – the first IMAX Dome installation. IMAX, Sydney Australia, the largest of any IMAX or any other screen in the world. [edit] External links IMAX, the official Web site The-Numbers.com, IMAX box office figures