Overall introduction to IMAX theater

IMAX was invented by three Canadians: Graeme Ferguson, Roman Kroitor and Robert Kerr. At the 1967 World's Fair in Montreal, their multi-projector large-screen projection system encountered many technical problems, prompting them to design a new single-projector, single-camera system.

The first IMAX film was shown at the 1970 World's Fair in Osaka, Japan, and the long-term IMAX system was installed in Toronto in 1971.

At the 1974 World Expo held in Spokane, Washington, the United States Pavilion displayed a giant IMAX screen of 27.3 x 19.7 meters. When the audience looked straight ahead, the picture was enough to fill the entire field of view. *** 5 million people have watched it. The vast majority of viewers think it shows a strong sense of movement, and a small number of viewers even get seasick. The screen was only on display for six months. A few years later, a full-size IMAX screen was installed at the Riverfront Park IMAX Theater and is in use today.

The first IMAX theater with a hemispheric screen opened in 1973 at the Ruben H. Fleet Space Theater and Science Center in Balboa Park, San Diego, California, USA. As of May 2003, there were 230 IMAX cinemas around the world, distributed in 34 countries, about half of which were commercial cinemas and the other half were educational institutions such as museums.

As of the end of 2009, there were more than 400 IMAX theaters around the world, distributed in 40 countries and regions. In developed countries and regions, the cost of building an IMAX theater is US$1 million to US$1.5 million. Due to the high cost of construction, movie theater investors often negotiate or pre-sign IMAX movie screening contracts with film distributors for a certain period of time in the future before investing and starting construction of IMAX theaters. In order to greatly increase the resolution of the image, IMAX uses a special 70mm film. The image size of a traditional 70mm film is 48.5 mm × 22.1 mm (Todd-AO), and the image size of an IMAX film is 69.6 mm × 48.5 mm. In order to expose at the standard film speed of 24 frames per second, IMAX films are advanced three times as fast as ordinary films.

There are certain technical difficulties in projecting large-format negatives - traditional 70mm negatives are not stable enough after being enlarged 586 times. Therefore, IMAX needs some new technologies. William Shaw of IMAX used an Australian patented technology called "rolling cycle" for film screening. It mainly added a compressed air device to accelerate the rolling of the film and put a cylindrical The lens is placed at the front of the projector and remains in a vacuum state during projection. The IMAX projector is fixed with screws. Four screws and gears hold the projector in a completely horizontal state. A cam control arm has also been added to counteract slight shaking during projection. The shutter length of the projector is also about 20% longer than that of conventional equipment, and the lamp brightness is higher. The largest 12-18 kilowatt xenon-arc lamps even require water-cooled electrodes. Therefore, the IMAX system is not cheap and weighs 1.8 tons.

IMAX’s film base is Kodak’s ESTAR (PET, DuPont Chemical’s Mylar®). The reason is not because of the strength of the film base, but because the film base will not be affected by the development chemicals. In addition to size, IMAX's film feeding equipment has strict requirements for changes in film side holes or thickness. IMAX films can be classified as "15/70" films, which means that each frame of this 70 mm film has 15 side holes. IMAX films are very bulky, and the film reels are much larger than those of ordinary movies.

In order to make full use of the film area, the IMAX film does not have a sound track. It uses a six-channel 35mm tape to play the sound synchronized with the picture. In the early 1990s, the digital six-channel sound source separated from the picture was changed to a more precise pulse generator as the synchronization signal source of the traditional SMPTE time code. This was the predecessor of future cinema multi-channel systems such as Dolby Digital and DTS.

IMAX continues to develop, and new expression techniques have emerged, such as three-dimensional images and a frame rate of up to 48 frames per second.

As for the sound system, there are Sonic-DDP (Direct Disc Playback, uncompressed LPCM surround track), stereo sound system and oval-shaped speaker clusters. .

The structure of IMAX is also very different from ordinary movie theaters. Due to the improvement in picture resolution, the audience can be closer to the screen. Generally, all seats are within the height of one screen (the seat span of traditional theaters can reach 8 to 12 screens). In addition, the seat inclination is also larger (in the case of hemispherical screens) The screening room can be tilted up to 23 degrees) so that the audience can face the center of the screen. IMAX Dome / OMNIMAX

IMAX Dome (formerly known as OMNIMAX, Chinese translation of Full Sky Movie) is used for projection on tilted hemispheric screens such as planetariums. This system uses a fisheye lens to capture a 180-degree scene on a flat film. Using another fisheye lens during projection allows the panorama to be reproduced on the screen. The horizontal projection angle of IMAX Dome is 180 degrees, while the vertical projection angle is 122 degrees, of which 22 degrees are below the horizontal line of the projector and 100 degrees are above the horizontal line of the projector. This is designed to match the tilted hemispherical screen. Some planetariums (such as the Hong Kong Space Museum) use hemispheric screens without tilt, so the image is always higher than the horizontal line of the projector, and the audience's seats are tilted further back than in ordinary theaters.

IMAX 3D

A three-dimensional version of IMAX technology. In order to create a three-dimensional depth of field, IMAX 3D uses dual cameras and dual projectors for shooting and projection.

IMAX 3D uses polarized light projection, and you need to wear polarized glasses to analyze the three-dimensional images when watching. Most IMAX 3D theaters use linearly polarized lenses. Some other companies use circularly polarized glasses. Circularly polarized eyes are less affected by the rotation angle of the glasses. When the audience tilts their heads, the effect is basically not affected. Unlike linearly polarized glasses, when the audience tilts their heads, the three-dimensional image will appear virtual. film.

IMAX HD (48 frames/second)

The new version of IMAX technology increases the frame rate from the original 24 frames/second to 48 frames/second to reduce the problem of screen flickering. Published at the 1992 World Expo in Spain. However, it was abandoned in 2000 because the cost of filming was double that of ordinary ones.

IMAX Digital (Digital IMAX)

The latest IMAX technology released in 2008. The projector is supported by DLP technology. The digital IMAX resolution is 2K, which is the same image quality as ordinary digital projection. , because its resolution is much lower than that of film IMAX. In order to ensure that the clarity of the movie picture will not be reduced due to the enlargement and projection of the giant screen, the digital IMAX screen has been reduced a lot, and even the screen is only 8.2 meters high (digital IMAX at Budweiser Show Cinemas in Kaohsiung, Taiwan). IMAX's original "giant screen" Screen, ultra-high picture quality" both are lost.

The advantage of digital IMAX is that it avoids the disadvantages of the bulky 70mm film, and the picture is bright and clean.

IMAX is expected to launch a new technology - laser digital IMAX in 2013. The projection resolution will be increased to 4K, and the color presentation will be better than the previous digital IMAX. Laser digital IMAX will improve the resolution problem of previous digital IMAX and maintain IMAX's original 1.43:1 screen ratio. It can still play the complete movie content when the IMAX camera shoots the picture.

DMR

Digital Media Remastering can be translated as digital remastering technology. In order to promote its theater system, IMAX has launched a DMR technology that can be used in the release of more commercial films. First, the production company gives IMAX a 35mm negative copy of the film, and then IMAX scans each frame at the highest resolution, sharpens and reduces noise on each frame, and finally prints it on 70mm negatives.

In the fall of 2002, IMAX and Universal Pictures jointly launched the IMAX version of Apollo 13 (1995), which was the first time that IMAX's exclusive DMR remastering technology was used to convert a traditional movie into the IMAX format. Some other films that have been released, such as Star Wars, have also been processed by DMR technology and put on IMAX. Due to technical constraints, the maximum length of videos processed by DMR in the early days was no more than 2 hours.

In 2003, The Matrix 2: Reloaded broke through this limitation and became an important milestone in the development of IMAX. In late 2003, the sequel The Matrix: Revolutions became the first film to be released simultaneously in IMAX and traditional theaters.

Viewers generally have a positive attitude toward IMAX films that are enlarged and produced using DMR technology. The visual and auditory enjoyment brought by these films far exceeds that of traditional 35mm films. A typical example is an audience member who watched "Apollo 13" who commented: "The huge screen, explosive sound effects, and James Horner's soul-stirring original music can only be felt in IMAX."

Both DMR and digital IMAX projectors are seen as a commercial compromise for IMAX rather than a radical technological innovation. DMR upscaling technology is not comparable to producing movies directly into the 70mm 15-hole IMAX format. Most DMR movies are in 16:9 or 2.35:1 widescreen format, so they cannot fill the entire IMAX screen when shown, and can only fill to about one-half ratio. The IMAX logo at the beginning of an IMAX movie fills the screen of the short, while the actual film is in widescreen. Some films, such as "Transformers 2", although the entire film is in wide screen, when certain clips shot on film are played, the screen will stretch to fill the screen. The resolution of DMR cannot be compared with that of 70mm film, especially since many films use digital cameras and post-production effects, so even DMR can only achieve 2K resolution. For example, the film version of Avatar only has a native resolution of 2K. People who are obsessed with the big screen will think that the decline of Cinerama technology occurred roughly at the same time as the original processing method was replaced by new, simpler and lower-cost methods, and DMR is just an important symbol.

IMAX originally only put the "IMAX Experience" logo on movies shot in real 70mm. It may use this slogan on movies that can be enlarged with DMR technology.