Robert Pattinson overacted in 'The Batman' to make the Dark Knight's emotions visible since half of his face was covered

• "The Batman" director Matt Reeves told Insider it was "hard" to make the Bat's emotions visible.
• Robert Pattinson thought Reeves was wrong until he saw his performance for himself.

One of the biggest challenges of playing Batman is showing emotion while most of your face is covered behind the famous cape and cowl.

Director Matt Reeves and star Robert Pattinson told Insider it wasn't easy to capture on film.

"We had no idea how hard it was gonna be," Reeves told Insider last week during a Q&A with the press after a special screening of "The Batman" on the Warner Bros.' lot. "There were times when I would come to Rob and go, 'OK, great. I just need to feel a little more and he'd be like, 'More?'"

"I'm about to have an embolism," Pattinson chimed in, joking about what it was like for him on set to hear those words from Reeves.

"Yeah, he was about to burst a vein," Reeves replied.

Reeves pointed out that Batman movies usually don't feature a lot of long dialogue scenes with Batman in his mask. The Caped Crusader isn't exactly known for being the chattiest of comic-book characters. So, it's vital that the hero can be expressive in subtle ways, especially with his eyes.

"Sometimes we couldn't even see your eyes, right?" Reeves asked Pattinson, recalling the challenges they faced making the movie, which sometimes resulted in them needing to do numerous takes of the same scene to get it just right.

"One of the things I love to do when I'm working with actors is say, 'Well, come take a look,' and you'd be like, 'How can that not be enough? I'm overacting. It's ridiculous,'" Reeves said, referring to Pattinson. " And I say, 'Come take a look, Rob,' and you go, 'Oh, you can't see my eyes.'"

"That was maybe the worst day of the whole shoot because I really genuinely thought it was you that was wrong," Pattinson admitted to Reeves' surprise. "I was like, how can we be doing 40 takes of this?"

"And I was looking at it. I'm like, 'Wow. I just look like I'm — There's nothing. There's nothing happening," Pattinson recalled of realizing Reeves was right while laughing.

Producer Dylan Clark added there was a day on set where Pattinson kept insisting to the crew that he was looking left in the cape and cowl. Pattinson later realized you couldn't tell what direction he was even trying to look.

"Can I say he is the most lovely gentleman, wonderful person? I had no idea that he ever thought I was wrong. I had no clue," Reeves said.

Pattinson's '40 takes' paid off and the proof is in the trailers

A great example of Pattinson's expressive Bat eyes is teased in trailers. As Batman chases the Penguin in his Batmobile, there's a brief moment where you can see one of Batman's eyes get slightly larger than the other, as if he's surprised by the situation in front of him.

That sort of playful eye expression is something you usually see more pronounced in animated versions of Batman, but in "The Batman" it was translated in live-action and it feels like you instantly know what's going on in the vigilante's head.

"It's a true testament to Rob as a performer," Reeves said. "He's so technical as well as incredibly emotional. I would watch Rob get himself into that state where he would be getting really raw before we would shoot and then I would be saying like, 'I think I need to see a little bit more through the cowl.'"

"It was definitely by design and it was a huge challenge. And thank God I had Rob to work with," Reeves added.

"The Batman," also starring Zoë Kravitz, Jeffrey Wright, Paul Dano, and Andy Serkis is in theaters on March 4.