The Mind-Boggling Engineering Behind IMAX 15/70mm Projection

I saw a report last week that said more people are seeking out IMAX screens than ever before. And I only have experiential evidence, but my local IMAX screen is packed week in and week out.

If you’ve ever sat in an IMAX theater and bathed in the glory of a Christopher Nolan or Jordan Peele epic, you know there is absolutely nothing like large-format celluloid.

It's the most transcendent way to watch a movie.

But what actually goes into getting that colossal strip of film onto a 90-foot screen?

Adam Savage's Tested recently took a trip to IMAX's Los Angeles headquarters to demystify the gargantuan logistical effort required to physically screen an IMAX 70mm film.

So today, we have a breakdown of the wildest behind-the-scenes secrets of IMAX 15/70mm projection.

Let's dive in.

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1. The Jaw-Dropping Scale of 15/70

IMAX film isn't just large; it’s massive. The format runs horizontally through the projector and features 15 perforations for every single frame.

Now, that probably doesn't mean much to a normal person, so let me give you something you can imagine. Because of this orientation, the physical image area is nearly ten times the size of a standard 35mm frame.

Here's another thing I'm not sure that I knew.

While standard 35mm film has to share its physical real estate on the actual celluloid with an optical soundtrack, every square millimeter of an IMAX frame is dedicated entirely to visual fidelity.

The sound is separate. It gets ingested from an optical disc into a hard drive system, which perfectly syncs up with the film's frame rate.

2. Film So Heavy It Requires Custom Architecture

The incredible resolution of 15/70mm comes at a severe physical cost: weight. I actually once had to pick up those reels and it was intense. My shoulder still hurts.

Here's a few facts I bet you didn't know:

• A single hour-long reel of IMAX film weighs roughly 300 lbs.
• A larger 68-inch reel, which holds just shy of three hours of footage (enough for a modern blockbuster), tips the scales at a staggering 600 lbs.

Because of the sheer mass of these prints, IMAX staging rooms are equipped with massive, custom-built rewind tables that are "the size of an apartment".

This is why we don't have as many of these theaters right now, about IMAX is expanding more theaters across the world.

Technicians use two distinct types of splicers for handling the massive strips: a temporary "zigzag" splicer (which allows the film to be pulled apart and put back together like a puzzle to swap around dailies) and a permanent straight splicer that practically welds the film together for its final presentation.

3. The Gravity-Defying Projection Path

If you want to know how IMAX can actually project at this size and weight, it;s actually kind of a whacky process.

When it’s time to screen one of the massive reels, the film physically travels on rollers 30 feet up into the ceiling to reach the second-floor projection booth, snakes through the projector, and then travels 30 feet back down to a take-up reel on the ground floor.

Now, this isn't how they'd do a Nolan or Peele movie, they come in giant cann=iasters and those projectionests get help loading them.

Regardless, the film zips through this dizzying loop at an astonishing 337 feet per minute. By comparison, standard 35mm film cruises at just 90 feet per minute.

If you're doing a 3D IMAX movie, this entire wild process is doubled. They have two separate massive prints running into the ceiling simultaneously for the left and right eyes. That gets very expensive.

4. The Booth: Rails and Dual-Lasers

Up in the David Keighley Theater projection booth a the IMAX HQ, the entire projection setup sits on a heavy-duty rail system.

That makes it easier for technicians to slide the massive projectors in and out of place. That lets them switch from a digital screening back over to 70mm film in just five minutes.

For their digital IMAX screenings (which is probably what you have at your IMAX theater), they actually utilize two digital projectors that auto-calibrate and converge their images.

Summing It All Up

The idea of shooting on IMAX and then projecting it is daunting, but will always remain a dream for most filmmakers. Even in reading all of this, I still think the future of movie-going are screens that are IMAX, and we need to expand their reach to draw more people into the theatrical experience.

Let me know what you think in the comments.