How ‘Oppenheimer’ Pulled Off an Atomic Bomb Explosion Without CGI: A Giant Aquarium, Balloons and More

variety.com:

Jazz Tangcay Artisans Editor In 2020’s “Tenet,” Christopher Nolan blew up a 747, and for his latest feature, “Oppenheimer,” he recreated the Trinity Test without using visual effects, opting to find a way to do it in-camera instead. “Obviously, we couldn’t make an explosion the size of the actual explosion so we used trickery,” cinematographer Hoyte van Hoytema explains, and no, they didn’t detonate a real atomic bomb.

The ten-minute sequence capturing the first-ever successful atomic bomb detonation came together through many experiments. It was a given that Nolan would do the scene in-camera. “We’re suckers for this absolute depth of resolution that IMAX give us,” van Hoytema says. “But when you go to VFX, you have to scan it, and the moment you do that, it loses half of its resolution.” Their goal was to preserve the quality of the film stock.

Despite not using VFX, Nolan and van Hoytema worked closely with special effects supervisor Scott Fisher and visual effects supervisor Andrew Jackson on a number of experiments to see how the scene could play out.

Van Hoytema says, “We created science experiments. We built aquariums with power in it. We dropped silver particles in it. We had molded metallic balloons which were lit up from the inside.