Imax

IMAX The IMAX (Image Maximum) system has its roots in Canada where multi-screen films were the hit of the fair. A small group of Canadian filmmakers Graeme Ferguson, Roman Kroitor and Robert Kerr decided to design a new system using a single, powerful projector, rather than the cumbersome multiple projectors used at that time. The result is the IMAX motion picture projection system, which would revolutionize the giantscreen cinema.IMAX delivers just that on a screen four times the size of conventional movie screens. Multi channel digital sound with excellent picture quality gives the viewers the feeling of being present in the scene been shown.

IMAX movie screen as compared with conventional screens

IMAX was premiered at the Fuji Pavilion, EXPO '70 in Osaka, Japan. The first permanent IMAX projection system was installed at Ontario Place's Cinesphere in Toronto in 1971. IMAX Dome (OMNIMAX) debuted at the Reuben H. Fleet Space Theatre in San Diego, CA in 1973. Sonics Associates of Birmingham, Alabama developed the IMAX digital sound system. In 1993, Sonic introduced the IMAX 3D sound system with 10 channels. IMAX -3D is a new motion picture process that creates the illusion of depth (or 3D) by projecting on the screen an image for the right eye, then an image for the left eye (30 times per second). Special goggles allow only one eye at a time to see the screen. The liquid crystal goggles are in sync with the projector via infrared signals beamed at the goggles on your head.

Goggles used in IMAX- 3D Systems

Theater speakers produce 8 channels from 4 CD disks synchronized with the15-perforation 70mm filmstrip running through the projector horizontally past a 15,000-watt lamp at 48 frames per second. The 3D headset has 2 additional channels for the binaural Personal Sound Environment (PSE). Binaural sound emanates from the headsets' two small speakers, just above and slightly in front of your ears; they cover all but the frequencies below 100 Hz. Low bass is handled by a pair of subwoofers behind the giant screen. Four full-range speakers, also behind the screen, keeps sound tied solidly to the films image even if you turn your head; if you have trouble imaging binaurally (as some people do), these speakers will prevent front sounds from seeming to come from the sides or rear. Two more speakers, in the rear of the theater, carry only surround ambience; the headset's binaural speakers carry sounds that are supposed to originate behind you. Eight channels of an 18,000-watt, 10-channel amplification system feed the speakers; the other two channels feed the binaural signals to the headsets. These amps are fed from four audio CDs, computersynchronized with one another and with the projectors. The headsets can receive four separate soundtracks, so a movie could be presented in different languages simultaneously if the theater provides enough channels. The difference between the IMAX sound system and the surround systems in conventional theaters is that the typical IMAX screen is close to a conventional 4:3 aspect ratio, but much, much bigger. So you have a great deal of vertical, which gives you the opportunity to do a 'voice-of-God' loudspeaker. IMAX system power varies depending on the size of the room, but it is typically in the range of 12,500 watts. The power is not there for the loudness; it's there for clarity and freedom from distortion. The

enclosures are three-way systems using components custom-designed and manufactured to specifications and combines four low-frequency loudspeakers in each cabinet with nested high- and mid-frequency horns. Using a sub-bass system for the deepest low sounds minimizes phase coherence problems. In most installations there are eight sub-bass loudspeakers each with in a 16-cubic-foot enclosure. The enclosures include a filtering labyrinth that physically traps the higher-frequency components that can otherwise cause overtones and distortion. Another distinction between IMAX and other theater surround systems is that it uses no digital audio data compression. The DDP (Digital Disk Playback system) is full fidelity "double-system" approaches, meaning that the sound is not recorded on the film itself. DDP uses three CD-Audio discs with a patented sample-accurate playback synchronization system. DTAC, the company's newest system, plays back audio files either from DVD-ROM or from a built-in hard disk. Unlike traditional flat-screen IMAX ® theaters, the new, Hackworth IMAX ® Dome Theater features a giant eight story domed screen and sixchannel, digital wrap around sound with 13,000 watts of power coming from 44 speakers. It seats 295 people in special reclining chairs that accentuate the feeling of actually being in the movie. The Hackworth IMAX ® Dome Theater is the only theater of its kind in Northern California.

Hackworth IMAX® Dome Theater

The technology that makes IMAX unique comes into play during the production process, when film 10 times the size of standard movie images is loaded into a 52-pound camera. Each IMAX film frame is roughly the size of a business card. IMAX film cartridges, which weigh nearly five pounds when fully loaded. Larger film translates into sharper images on the movie screen, which isn't actually a traditional, flexible screen at all. Instead, 340 perforated aluminum panels have been pieced together like an igloo to

form the projection dome. Nearly a quarter of the dome's inside surface is actually tiny holes, put there to allow sound to pass through from the 44 speakers concealed behind the panel.

Projector

Projecting the film is a technological feat in itself. The movie is stored on reels the size of tractor tires that must be loaded onto a hand-built projector. The loading process is done beneath the theater, inside a dustfree projection and operator's room and visible through windows as the audience prepares to enter the Hackworth. At the start of the show, the entire two-ton projection package is lifted on an elevator some 22 feet into a box, called a "dog house,'' built into the theater's seating area. Film passes behind the lens at the rate of 51/2 feet each second. A typical 40-minute IMAX movie requires moving more than 3 miles of film through the projector. The 15,000-watt xenon lamp used to project the image onto the screen is so bright that, if it were placed on the moon, it could be seen from Earth. The lamp's surface reaches 1,300 degrees Fahrenheit, requiring a cooling system to pump five gallons of water and 800 cubic feet of air around the bulb each minute. Unlike typical commercial movies, the sound for the Hackworth's IMAX films is not embedded in the film stock. Instead, the digital sound is played from a compact disc and is synchronized with the images by a special audio controller. India’s first IMAX theatre has been set up in Mumbai this year. It has a dome screen of 30m diameter that offers viewers a real-life experience. The theatre screened The Blue Planet and The Mysteries of Egypt in the inaugural shows.