What is IMAX?
What is IMAX? As soon as you walk into this theater, the difference in this format is immediately apparent, the screen is gigantic! There are two types of IMAX theaters. The ‘standard’ theaters and the dome theaters.
A standard IMAX theater has a huge rectangular screen. A typical IMAX screen is 16 feet high by 22 feet wide, but they can be much larger. The largest screen is 30 meters high. Imagine standing next to an eight-story apartment building that is wider than it is tall. That’s how big the screen is! It is many times larger than the screen in a normal cinema.
An IMAX dome provides a semicircular screen that envelops the entire theater. Domes can be up to 30 meters in diameter.
Whether you are in a theater or a dome, the effect is astonishing. The screen is large enough to fill your field of vision. By doing this, the screen gives you an incredible sense of immersion (there’s nothing outside of the movie to divert your attention), and it also enhances the sense of movement. In fact, the sense of movement is so strong that it makes some people feel nauseous.
How does it work?
To fill the gigantic screen with a clear image, the films are recorded and printed on huge film stock that is unique in the film industry.
Most of the movies you see in a theater have a size of 35 millimeters. The frame is 35 millimeters wide and almost square. But movie screens are not square – they are very wide for their height. The wide image is thus compressed to the 35 millimeter frame and enlarged by the projector to fill the screen.
Some theater films have a size of 70 millimeters. This format offers about double the resolution and the frame is of course the width of the screen, so there is no compression.
This film is also referred to as the 15/70 film format. Each frame is 70 millimeters high and 15 perforations wide. In other words, the film size is approximately 10 times larger than standard 35 millimeter film. This film size gives an IMAX movie incredible clarity, even on the large screens in IMAX theaters.
The IMAX projector
The 15/70 film format makes an IMAX projector a truly unique device. If you’ve read how movie projectors work, you’ll understand the basic mechanism of a 35mm projector:
- The film is fed in from the top of the projector.
- A claw or gear arrangement advances the film one frame and keeps it stable in front of the light.
- A shutter opens and allows light to shine through the film and lens onto the screen for a fraction of a second.
The film is so heavy and large that a projector, so to speak, requires a crane to move it, and it is difficult to keep such a large film frame perfectly flat in relation to the lens. Therefore, this projector is completely different from a normal projector:
- The movie moves through it horizontally instead of vertically.
- A vacuum system sucks each image onto a piece of glass in front of the lens so that the image is perfectly oriented in front of the lens.
- The shutter opens longer than a normal projector to let in more light. The lamp for the projector is a 15,000 watt water-cooled xenon unit .
All this advanced technology means that a projector like this weighs more than 2 tons (1,800 kilograms) – the weight of a small car! That’s what it takes to get such a crisp, clear picture on such a great screen.
The IMAX experience
IMAX provides very sharp images and better contrast, allowing you to immerse yourself in the film. What does that look like?