28 Days Later was famously shot on digital video, which had a very homemade feel to it but also was one of the reasons why the film was so unique and ultimately successful. So when it came time to make the new film, the team’s attempts to figure out unique production methods was partly inspired by that initial approach 23 years ago.

Several production techniques were used in an attempt to achieve that immersive feeling, including attaching cameras to actors, special sensors, designing rigs to house multiple cameras, drones, and working with a wide variety of camera types and lenses. And that included three special rigs for the iPhone sequences.

“One for eight cameras, which can be carried very easily by one person, one for 10 cameras, and one for 20,” explains the director of the iPhone rigs. “I never say this, but there is an incredible shot in the second half [of the film] where we use the 20-rig camera, and you'll know it when you see it. … It's quite graphic but it's a wonderful shot that uses that technique, and in a startling way that kind of kicks you into a new world rather than thinking you've seen it before.”

Boyle equates the 20-camera rig to “basically a poor man’s bullet time.” It allows flexibility for the filmmakers in terms of light and ease of use on location shoots, and it can be attached to cranes or a camera dolly or built into a location even.