Patrick Stewart’s general policy when he receives a script is, if it looks like it won’t be very interesting, he just reads it on his computer. But if it looks like a cut above, he prints it out and settles in with it.

When Jeremy Saulnier’s “Green Room” (currently in limited release) came his way, he printed it out. He began reading the thriller, about a punk rock band under siege by neo-Nazis in a remote performance venue, early in the evening. Then it got dark. After about 35 pages, he closed the script, went around his West Oxfordshire home checking all the doors and windows and then set the perimeter lights and alarm.

“It had got to me so fast, and potently,” the actor says. “I poured myself a large glass of whiskey and then I finished reading the script.”

Saulnier, meanwhile, was about two weeks away from shooting without having cast Darcy Banker, the cool, collected white supremacist antagonist of the film. “It was really getting unbearably stressful,” he says.

Someone at the pair’s mutual management company had suggested Stewart’s name, and the director pounced.

“He kind of swooped in to save the day as far as adding so much value to the investment that our financiers were putting forward to make the movie,” Saulnier says. “And of course, that is not a concern to me at all. I just want someone who’s a dedicated actor who can bring a certain amount of craft, and he sort of satisfied both of our needs.”

It was serendipitous timing, as Stewart was on the hunt for something new. But the project was also in line with his ongoing creative philosophy in the business.

“Whether it’s actors or directors or producers or designers, I am always looking for the opportunity to work with people who are creatively new and excited and ambitious within the industry,” Stewart says. “It can help to make a wonderful working relationship.”

There wasn’t much time for Stewart to prepare for the role, however. It was about 10 days between reading the script and hopping a plane to Portland, Oregon for the shoot, but he says he finds that sort of chaos exciting, when something comes from out of the blue that he feels he can’t pass up. “Even though you might be enjoying sitting in your rose garden in Oxfordshire, the other thing becomes more important,” he says.

On set, things were a bit unusual as well. There wasn’t much time for conversation as Saulnier had already begun shooting the film. And Stewart did not socialize with co-stars like Anton Yelchin, Imogen Poots and Alia Shawkat much at all. That was good for him, though, because Darcy is very much isolated with his own group in the film. He doesn’t come face-to-face with the punk rockers his gang has been terrorizing until the end of the movie.

“It was appropriate that we didn’t know one another,” Stewart says. “We stayed within that serious, threatening, rather remote and isolated world that Jeremy was creating.”

Adds Saulnier: “He was quiet and understated and I think commanded such a huge level of respect that it really sold the pragmatism of this character. Because, despite the chaos and brutality of the night’s events, it ultimately is a reluctant mop-up operation and not a nefarious plot to dispatch these young kids. It was really kind of exciting and he has that quiet command.”

A lot of Stewart’s inspiration came from Saulnier, who has roots in the punk scene himself and based a lot of the characters and interactions on people he knew. But the actor did do some research on white supremacist groups in the United States.

“I was fascinated to find that the heartland of such a movement was in fact the Pacific Northwest, which traditionally I had always associated with a very liberal, very open, kind of socially-minded part of the United States,” Stewart says. “That these groups existed there was very surprising, which is what made me very interested in the recent incidents that have been happening there of the people who took over this area of land and basically created a separate sort of nation out of it. So that was very valuable.”

Saulnier came up as a cinematographer, graduating from NYU’s Tisch School of the Arts in 1998. But he entered the industry during the awkward early growing pains of the move to digital standardization.

“In film school, there were two questions: 35mm or 16mm,” he says. “Maybe you’d say, ‘Well, is it fresh stock or is it short ends?’ But I was lost when film became less affordable and digital video became the standard, because I thought it looked terrible.”

He was forced to shoot his debut feature, 2007’s “Murder Party,” on poor-quality standard definition video. This was four years after he shot his short film “Crabwalk” on 16mm and had felt emboldened by the beautiful results.

“I love ‘Murder Party,’ and it’s genuinely appreciated by a lot of genre fans out there, but the aesthetic wasn’t nearly as cinematic as I wanted it to be,” he says.

That’s when he focused on his cinematography career and learning the craft, while simultaneously, cameras began getting smaller and cheaper. He had to wait out the digital revolution for a while, until it finally became affordable enough at a certain level of quality. Soon, after having invested and lost so much in “Murder Party” — including his wife’s retirement fund — he was comfortable heading back into the breach for a follow-up: 2014’s “Blue Ruin,” which won a prize at the 2013 Cannes Film Festival.

“I shot it on a Canon C300 and it was a camera that I could own, and that was a big thing, to have total control over the camera package and the camera support,” he says. He also employed a lot of the run-and-gun techniques he learned shooting corporate videos in his time between features.

With “Green Room,” he finally hired a cinematographer — Sean Porter (“It Felt Like Love,” “Kumiko, the Treasure Hunter”) — so he could focus on the growing demands of the production. But even as the offers pour in and the possibility for larger opportunities looms, he’s keeping an eye on the fact that a certain amount of limitation is what has led to such creative strides in his career.

“A lot of my favorite directors, as they’ve hit a certain sweet spot and made their best movies, they go unchecked and their appeal is lost,” he says. “I don’t want to go unchecked. I think the key is I love notes. I love committees chiming in. I don’t like mandates, but if I’m the filter, then I’m very collaborative. But I did not sign up so I can fight people to have to explain what I want to make. I’d rather incrementally prove to people that I have a certain aesthetic and taste level that can be applied to certain movies.”