On a chilly February afternoon in Atlanta, Georgia, last year, hundreds of background actors filming a boxing-match scene for “Creed III” were asked to move from the arena they’d been cheering in to a large tent nearby. Once inside, they took turns sitting and cheering again, except now they were sitting by themselves in front of a circle of small cameras that filmed their movements in great detail. A production assistant behind the cameras held up cue cards. “Stand up!” said one. “Cheer!” said another. The scans would be used to fill out crowd scenes, they were told, making 200 human actors look like thousands.

Stephen Shutters was one of those actors, and he didn’t think much of it at the time. “No one did,” he says.