Paul Greengrass’ “Captain Phillips” is currently entering its second week at the box office having riveted both critics and filmgoers. Much of the praise the film has received has focused on its exceptional realism. Much of that is courtesy of the film’s director of photography, Barry Ackroyd, who spoke to HitFix earlier this week about his work bringing the saga to life.

Ackroyd previously worked with Greengrass on “United 93” and “Green Zone.” It’s clear they see eye-to-eye on most matters; both have backgrounds in documentaries and both are keen to make their films as realistic as possible and appropriately respectful of their subjects. “Sometimes you have to get a very blunt instruction,” Ackroyd says. “But when it’s working well, very little discussion is necessary. It’s an understanding that you have.”

Ackroyd says working with Greengrass is quite the immersive experience as the director is ever focused on placing the viewer in the story. “Paul is going to throw you into this world that is tough: ‘How do we film a war zone?’ With some directors, you’d have to find some highly technical way with CGI. But with Paul, it comes down to ‘let’s just do it.'”

There was discussion as to whether “Captain Phillips” should be shot digitally, and in that realm of cinematography’s consistent evolution, Ackroyd says he’s quite flexible. But in the end, “it’s about texture and reality and grain,” he says, so they “decided to go with something more reliable.”

Old-fashioned problems regarding practicality began to emerge, naturally. “You start to find out the limitations,” Ackroyd says. “Once we realized what we had to achieve – fishing boats in high seas chasing a rather large container ship, etc. – then we’re going to have to be as flexible as we can. I can’t carry the zoom lens on a 35mm format. It had to be 16mm, and that’s going to have to capture the story.”

Ackroyd and Greengrass are also famous for their use of the hand-held camera. Ackroyd says he likes the change to, again, capture things in a real-time vein. “It becomes a natural process,” he says. “You can put it on a little tripod with a slider. I also use long lenses, long zooms. Soon, where the camera goes, your mind goes. During each take, it’s organic to know when to run at someone, when you let someone come to you.”

This is not to say that much of the film wasn’t daunting, and Ackroyd knew there would be challenges as soon as he read the script. “Undoubtedly when you read a script set at night with three navy war ships, a lifeboat and a helicopter and the lifeboat needs to be taken down, you’re going out there thinking it can’t be done,” he says. “But with someone like Paul Greengrass, you’ll know he’ll be supporting you.”

Even with Ackroyd’s background in documentaries and filming around the world, each new project poses new challenges, and this title was no exception. “I’ve been about everywhere and every place,” he says. “I actually filmed on an aircraft carrier in the Gulf War. I have lots of familiarity with container ships. The bridge or engine room of a ship wasn’t a surprise to me. But taking down a cargo ship at sea was something I hadn’t done before.”

In the midst of the grandiosity of the ships at the heart of the plot, it became very important not to forget what the film was about: the story of an individual and his crew. Truth in a story, he says, “is not something you can reproduce,” which is an interesting takeaway given the criticism the film has come under as of late. But that’s not to say it isn’t a goal.

“Once you’ve decided on a technique, basically you’re talking about how to represent different parts of humanity clashing together in the way they do in the film,” he says. “I need to put the camera on and treat the subject with the dignity that it deserves, whether it is the navy or the captain or the crew of the Alabama or the pirates.”

Ackroyd particularly remembered one moment of honesty and drama when Muse [the leader of the Somali pirates] comes out with the line “look at me…I’m the captain now.” Actor Barkhad Abdi “has the audience and then the captain of the ship,” Ackroyd notes. “It’s precious and you have to be ready. That’s what I’m doing constantly, all day…asking where to position cameras to capture ‘that moment.’ Iit’s kind of a chess game.”

The film has been praised for the neutrality with which it shows its events and the empathy with which it depicts the pirates. For Ackroyd, this was exciting. “It was walking in there, handheld, documentary-style, using every frame of the shot to tell the story,” he says. “But that only exists in the background of an incredibly large panoply, a juxtaposition of two totally different worlds.”

In order to create the feel of the film, it was shot, insofar as possible, sequentially. Ackroyd was convinced this natural “building from beginning-to-end approach” was crucial. “I’ve done that in a lot of films,” he says, particularly noting director Ken Loach, who employs the technique with absolute rigor. “Your rehearsal for the next scene is what you did just before it. You know where you’re coming from and where you’re going is a bit of surprise. For example, when the Somalis take the bridge, no one knew exactly what would happen. Tom was surprised. And he had been kept away from the Somali actors. There was shouting in Somali…he had no idea what they were saying.”

Of course, Ackroyd did roughly know where he was going, which was essential but also difficult as the audience was only meant to know as much as the characters. “Sometimes you get drawn into a shot and it takes you somewhere, but it’s not part of the story yet,” he says.

Multiple cameras were operated at once to ensure the audience got to see the scene from different angles if need be. Greengrass insisted on keeping some cameras running even when it seemed extremely unlikely that the shots from the camera would be used. And whenever capturing something of this magnitude, it was important to know what the audience would see next. “We’d always have to keep the cameras running and I’d have to see it as a whole,” Ackroyd says. “I’m trying to look around the corner – need to see the helicopter turning and then something on the boat itself. That’s kind of the thought process. I’m not trying to plan one shot. I’m trying to plan four.”

At the end of the day, all this work built up to an incredibly suspenseful film that is visually arresting, to be sure, but also one that said something deeper. It was the final scene of the film that got to Ackroyd the most. “It’s the scene lots of people are talking about,” he says. “The end sequence of any film has to be powerful. We had versions of how this film would end. But none of us conceived of what we were going to do until we actually did it. It involved Tom pulling out things in his psyche.”

Throughout the production, Ackroyd sought to not only keep his audience riveted as if they were watching real-life events unfold, but also keep them involved in a story about the human condition. “Humanity is pretty readable,” he says. “And that’s universal. I’ve filmed in 50-60 countries and we are all pretty much the same.”

“Captain Phillips” is now playing in theaters nationwide.