The Stunt People wanted to show a side of Darth Vader that not many have seen before, and that's what he sees when slicing enemies with his lightsaber. So, they strapped a GoPro Hero 3 to him to capture the epic battle from a first-person perspective. Continue reading for more.
As you can see, they switch to the Jedi's point of view, complete with The Force, halfway through the battle. If you're wondering about the actual lightsabers, they used modified Hasbro Ultimate FX models "with the LED light strips removed and replaced with a single LED."
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