According to the visual effectes supervisor on The Falcon and the Winter Soldier, Captain America's shield has to be replaced digitally in many of the series' key shots, especially fight scenes where, for safety reasons, you can't use a real, metal shield. The rubber one they use in most of those scenes is a good way to get accurate reactions and to give the actors something to work with, but it's rubber, so it bends -- something an unbreakable, vibranium shield isn't known for doing. That means, of course, that the bloody kill undertaken by John Walker that became a viral part of the conversation around the series was also done using a digitally-replaced shield.
Digital effects are seen in virtually every inch of big-budget superhero productions like the Marvel movies and, now, their TV tie-ins. Fans are often surprised, though, when they realize that computers are used for simple things like replacing props and making simple tweaks in post-production.
"The one thing that I think was pretty invisible and really successful was that shield needed to be replaced in almost every shot," said Eric Leven, VFX supervisor for the series (via CinemaBlend). "One of the most impressive shots I thought was at the very end when Sam’s holding up the shield after the fight and wiping the blood away. That’s a CG shield with CG blood on it. Due to the fact that one, it was difficult for people to decide on the day what the blood was gonna look like. People were frankly hesitant to put blood on the real shield, because we’d never done that before, this shield is always pristine. But when they’re fighting, they’re fighting with a rubber shield, they can’t fight with the real shield. So the rubber shields typically don’t look 100%, they flex, so that needs to be replaced….People don’t realize that shield is usually computer generated."
Following the events of Avengers: Endgame, Sam Wilson/Falcon and Bucky Barnes/Winter Soldier team up in a global adventure that tests their abilities — and their patience — in Marvel Studios’ The Falcon and The Winter Soldier. The all-new series is directed by Kari Skogland; Malcolm Spellman is the head writer.