A not-for-profit organization and online magazine for kids
Non-Fiction
Sci-Tech Kids! – The Wonder of IMAX
By Brad Bradshaw, Sci-Tech Kids! Co-Editor
Hello and welcome to the new Sci-Tech Kids! Column! My name is Brad Bradshaw and I am thrilled to be a new editor for Amazing Kids! The purpose of this new column is to help inspire and educate kids in the fields of science, engineering and technology. More importantly, though, we write because Sci-Tech is cool! Also included in this column will be interviews with Amazing Mentors!, successful professionals in science or tech fields, giving their insight into the realities of working in those fields.
The driving force in the Sci-Tech fields may be competition, the quest to build the biggest, the fastest, and the most powerful. Just as in the international race for the tallest skyscraper (have you seen the Dubai Tower), scientists have competed for years to construct the best, the biggest movie-watching experience. Enter the IMAX. This amazing system, projecting the largest picture in the world, may still be the paramount cinematic system. But how did it come about? Join me in exploring some of the history of, and the technology in, the IMAX system.
The IMAX system was developed by Graeme Ferguson, Roman Kroitor, Robert Kerr, and William C. Shaw, natives of Canada, for exhibition in the 1967 International and Universal Exposition of the World's Fair held in Montreal, Quebec, Canada. Their goal was simple: to build the largest and sharpest projection system in the world. And it was a smashing success. 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.
The theory behind the IMAX system is deceptively simple. In a movie theater, light is shined through translucent film, projecting an image on the screen. The further away the light source is from the screen, the larger the picture will be. However, as the image is “blown up” on the screen, it becomes increasingly blurry. The intent of IMAX was thus: to increase the size of the image on the screen while maintaining pristine resolution. Their solution was simple; increase the size of the film and the light source so that the image on the screen can be large, without having to move the projector further away. However, using 70mm film (the size in IMAX projectors) creates a series of new challenges. Movies are produced by flashing a series of images fast enough so that the human eye perceives them as a single, changing scene. To keep a movie from looking like a slideshow, the images must be projected 24 frames per second. Because IMAX film is so much larger than normal movie reels, it must move much faster, because three times as much film needs to move through the projector each second.In order to solve this problem, William Shaw of IMAX invented what he called the “rolling loop” system, which involves adding a compressed air puffer to accelerate the film without touching or marring the image. IMAX projectors utilize a cylindrical lens that vacuums up the film during projection and serves to flatten the image against the lens. This, along with precise balancing systems, allows IMAX film to obtain a resolution of 12000 X 8700 pixels, that’s 80 times more than a computer screen! A final problem in creating these projectors was the light source. How could they create an extra-large and super-powerful lamp for their camera that still produced daylight-quality light? Their solution was to fill the lamp with pressurized xenon gas and induce it to shine with a laser. This system creates white, continuous light. However, because the gas is under intense pressure and the laser generates lots of heat, the lamp could not be surrounded by glass, because it would melt and shatter immediately. Instead the lamps are surrounded by a layer of fused quartz crystal. In case one were to break, projectionists are required to wear protective body armor, because the high pressure of the gas would send sharp quartz shards flying.
The IMAX system provided a breakthrough in projection technology, allowing movies to become bigger and clearer than ever before. However, IMAX wanted to make its films even more lifelike. In the late 1960s the San Diego Hall of Science asked IMAX to design a large-format film system to project on the dome of their 76 ft planetarium. IMAX scientists had to head back to the drawing board to create both a new movie camera and projector for the dome. The camera utilizes a fisheye lens to capture a full 180o field of view onto film. The cameraman must film at a specific angle that matches the tilt of the dome. The project is then fit with a matching fisheye lens and projected onto the dome the original panoramic view is recreated, wrapping 180° horizontally, 100° above the horizon and 22° below the horizon for a viewer at the center of the dome. This awesome technique lends a view the experience of “falling” into the screen as it occupies his or her entire range of vision.
IMAX, having the biggest, clearest picture, is known for one more amazing feature: its 3D projection. There are two ways to create a 3D picture in a theater. The first involves polarization. Movies are filmed with two cameras, representing the left and right eyes of the viewers. During the showing, both images are projected onto the screen, but they are polarized in opposite directions. Viewers are given special glasses that cancel out respective images. The left lens is polarized so that it only allows the left-eye image to pass through, and the right lens only allows the right. Because of this, the picture looks three dimensional. The second method involves LCD shutter glasses. The movie is filmed in the same way, with two cameras representing the two eyes. During showing, the projector alternates between projecting the left- and right-eye images 48 times per second. In rhythm with the projector, the left lens will become transparent as the left-eye image is projected, while the right lens will remain opaque. In much the same way, the left eye will only see the left-eye image, while the right eye will see the right-eye image, creating a three dimensional picture. This incredibly realistic picture makes movies a truly amazing experience.
Back to Non-Fiction