Many of you may be aware that in the midst of the pelting rainstorm last night, a certain wizard was walking the red carpet in London’s Leicester Square. Yes, Harry Potter is back and I can’t wait to get my ticket! I first caught the trailer whilst watching a film at the BFI IMAX and was blown away by it. London has four of the UK’s nine IMAX cinemas (BFI, Science Museum, Odeon Greenwich and Odeon Wimbledon), and whilst the £13.50 price tag may seem steep for a film that you could see in any other cinema (though some IMAX’s will have “select scenes exclusively in IMAX 3D”), the technology required for such a cinema experience far surpasses that used in a regular cinema.
IMAX screens have been around since 1971, when the first was built in Toronto (and is still in use today). This fact will disappoint my housemate Dave as he is convinced the first one was in Bradford! Indeed, the Bradford screen was the first in Europe, but not quite the world (sorry Dave). Like normal cinema screens, IMAX screens vary in size. The biggest is in Sydney; it weighs in at over a tonne and measures an impressive 29.42m x 35.73, making it 10 times bigger than a normal cinema screen. For some reason, IMAX venues like to quote sizes in storeys and buses, so just for continuity, that’s about eight storeys by four buses.
The LG IMAX theatre at Darling Harbour, Sydney, Australia. Photo courtesy of Wikipedia.
The IMAX screens themselves are not actually that technologically different from regular cinema screens. A (very large) piece of vinyl is stretched over a scaffold frame and coated with reflective silver paint. However, most IMAX screens also have thousands of tiny perforations, allowing sound to be projected through speakers behind the screen, in addition to speakers in the cinema itself. The film soundtrack can then be delivered through a 15,000 watt digital surround sound system, enhancing the immersive experience.
The magic seems to lie in the IMAX camera and projector. There are 26 IMAX cameras in the world, and whereas conventional cameras shoot in 35mm mode, these cameras use 15/70mm film, which gives the film frames a higher definition and clarity. However, there are many films out there which have not been shot with the IMAX camera (26 is not that many to go around and 70mm film is very expensive). IMAX cinemas can get away with showing these by digitally re-mastering the 35mm Hollywood films through a process called DMR. It’s not an easy process though, taking a team of 20 technicians about three weeks to complete. Approximately 80% of the frames can be automatically rendered using uprezzing algorithms, but for the remaining 20%, the film grain must be painstakingly removed by hand, tweaking lighting and colour settings by minute degrees.
An IMAX camera in a display case. Photo courtesy of Wikipedia.
As for the projectors, these are cumbersome things weighing up to 1.8 tonnes! They are the most powerful projectors in the world. Their lamps could be seen from space and have a surface as hot as the sun, so cold water is continuously pumped through the system to stop various components from melting. But it’s not just this which makes the projectionists job slightly hazardous; the lamps are made from a thin layer of quartz crystal and contain xenon gas at a pressure of around 25atm. No-one wants a high pressure crystal exploding in their face so body armour is essential when handling the equipment, just incase a lamp gets dropped on the floor.
Fortunately for me, I have no plans to handle quartz crystal lamps anytime soon. Instead, I’m off to book my ticket to see Harry at the BFI. My favourite thing about the IMAX is the fact that despite there being 470 other people in the cinema, the angle of the seating provides a completely unobstructed view of the screen. And I have no scientific evidence to back this up, but my film-buff friend Catherine assures me that M20 is by far the best seat in the house.