The crazy 360 degree reference camera and the volumetric capture of Ezra Miller.
Warner Bros. has released an official behind the scenes featurette on how those Bary Allen twinning shots in The Flash were achieved.
You might normally used locked-off cameras or mo-co to do this work (and of course great comp), but The Flash employed a process of shooting with Ezra Miller and a body double, and then later shooting of same scenes again in a volumetric capture set-up with just Miller.
On-set, Ezra’s body double (Ed Wade) had a rod sticking out of his back on a Scorpion camera rig with a 360 camera on it. It would be shooting what would become Ezra’s eyeline for the ‘B-side’ of the scene (which was done in a volumetric capture booth).
The volumetric capture was done in a booth made up of more than 100 cameras that also included an LED screen, meaning Miller could see the scene he needed to appear in while performing the B side. This complete setup and workflow is tech from Eyeline Studios, I believe.
The idea, of course, as well, is that Miller was also being lit appropriately by that LED screen because the lighting came directly from the original shoot.
That gives the VFX studios, working under VFX supervisor John ‘D.J.’ Des Jardin, a full volumetric capture of the other Barry Allens needed for specific scenes, to place over Ed Wade’s head for final shots.
Check out the video below.