IMAX 101: Theatre Geometry (Video)

January 02, 2013 2:25pm
Source: IMAX

Have you ever wondered exactly what’s different about an IMAX® theatre? Well it’s not one thing; it’s a combination many elements, most of them unique IMAX inventions and patents. We recently discussed our proprietary sound system in the IMAX 101: Sound post and today we’re going to discuss what goes into the design of an IMAX theatre.

Check out our new IMAX 101: Theatre Geometry video to find out more:

IMAX’s theatre geometry refers to the shape of the auditorium and how the seats are placed. Most movie auditoriums are long and narrow, to get the most people in, with the screen way off at the far end. However, in an IMAX theatre, you’ll notice a distinctively different shape that is designed to bring you not only closer to the screen, but better-positioned in relation to it.

For starters, IMAX screens are wider, higher and slightly curved. Because the quality of the content playing is so high, we can bring audiences closer to the screen so it fills your peripherals. This creates a picture that’s so immersive, you’re not aware of where it ends. And that, in turn, is what gives you the feeling you’re part of the action, out among the stars, not just peeking into a scene.

Let’s say for example that you are watching a scene from a movie that takes place at the top of a tall building. In IMAX theatres, scenes like this can actually make you feel vertigo - giving you the feeling that you’re going to fall right out of your seat. Why does that happen? What makes you believe you’re actually going to fall?

As you’ve seen in the video, it all comes down to viewing angles and how they register deep inside your eye. The human eye contains two types of photo receptor cells: rods and cones. Cones are a part of your central vision and allow you to focus on detail. Rods are important to your peripheral vision and are critical for sensing motion and the feeling that you are falling out of your seat.

The average human has a horizontal field of view of 180 degrees. The central vision makes up quite a small portion of this field. As you move away from the center you gradually begin to lose the ability to see detail and shape. Beyond approximately 30 degrees your peripheral vision starts to take over that’s where you really start to sense motion.

A typical movie theater will play on screen view of 54 degrees. That just gets you into the peripheral view; a little on the left a little on the right. IMAX theatres are designed to increase the angles and open up the field of view to an average of 70 degrees, which goes a long way inside your eye. Each degree increase activates tens of thousands of additional rod cells, so even a slight increase from 54 to 70 degrees means hundreds of thousands more rod cells stimulated by the image on screen, per eye.

This increased sensation of motion is one of those things that makes you believe your in that world you see on-screen. So if the edge of the cliff scene is registered by rod cells in your eye your brain cells are going to tell your body to watch out for that cliff. This makes your experience at the movies more than just popcorn and snacks, it's an adventure to another world. That's what you get each time you see a movie in IMAX. Hope to see you soon in an IMAX near you.