2017’s Dunkirk may not have had the twisty plot that some Christopher Nolan films have, or a whole lot of memorable characters or dialog. But it did involve very impressive filmmaking. For example, to get clear footage of a plane crashing, Nolan dropped an IMAX camera worth half a million dollars into the sea.

We’re just estimating that price tag of $500,000, by the way, based on how much the insurance policy is on each camera. You might instead say IMAX cameras are priceless since you can’t buy them. You rent them, for some $16,000 per week per camera.

Which is worth it, considering the quality of IMAX footage. There’s no real way of conveying how good IMAX looks without actually sending you to a theater that uses IMAX 70mm film. Let’s put it this way: If you think you’ve seen an IMAX movie before, and it just looked a fair bit bigger and brighter than regular movies, you didn’t see a real IMAX movie. A lot of theaters use the IMAX branding but project digital images that are a lot smaller than real IMAX. Only a handful of 70mm IMAX theaters are still in operation.

Christopher Nolan is one of a few directors still passionate about using real celluloid—passionate to a fault, say fans of digital. He shot Dunkirk on film, and for one scene, the team placed an IMAX camera into the stunt plane they were sinking. They built a special frame around the camera so that even when it hit the water, it would stay totally protected.

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At least, that was the plan. But the plane didn’t float in the water like it was supposed to. It sank. The water broke through the frame and filled the camera. It spent 90 minutes in seawater before divers could bring it back up. 

And yet the footage they shot survived just fine. Celluloid is pretty much waterproof, which is one more advantage of using film (under extremely specific circumstances). 

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For more Nolan news, see also:

4 Christopher Nolan Movies No Other Director Could Have Made

5 Stupid Complaints We Always Have About Chris Nolan Movies

5 Specific Things Great Directors Can’t Get Right

Top image: Warner Bros. Pictures