The concept of the interview is endlessly interesting to me,” Errol Morris said with a wistful smile. The filmmaker tapped his fingertips together. “I have given interviews a lot of thought through the years, and I still think about them quite a lot. In a real sense they are a basic human relationship. But an interview is also an artificial frame, a focus, and that, well, that’s even more interesting.”

Morris, who won an Oscar for his 2003 documentary, “The Fog of War: Eleven Lessons From the Life of Robert S. McNamara,” has been described as a “detective director” for his probing, and often controversial, productions. Much has been made about his vivid use of reenactments, but the true axis of his work is the interviews he conducts, often with outsiders, unsavory figures or people haunted by personal history or public opinion. That is especially the case in his ninth film, “Standard Operating Procedure,” which opens Friday in Los Angeles, and looks for answers from the infamous guards at the Abu Ghraib prison in Iraq.

The film is a searing experience and a surprising one for many viewers. “I have heard from a number of people that the film is different on successive viewings, that it changes,” Morris said with quiet pride. The 60-year-old director has the ruddy mien and directness of a veteran East Coast cop but not the growl, and sitting at the restaurant of the Four Seasons in Beverly Hills, , the Boston filmmaker seemed especially blue-collar. “Larry Flynt is sitting over there,” he said. “I’d love to interview him.”

There is considerable debate already about “Standard Operating Procedure” and what it reveals (or omits) about the wrenching events at Abu Ghraib. Like many of the films Morris has made, its premise is that the “real story” has been missed, misunderstood or hidden and that through interviews and dogged investigation, the truth will out right there on the screen.

Morris began work on the film 2 1/2 years ago when he coaxed Janis Karpinski, who had been an Army Reserve brigadier general overseeing three prisons in Iraq, to sit down for an interview. It lasted 17 hours over two grueling days. “If I had told her that before we started, she would have run away screaming. Instead she talked and talked and talked and got angrier and angrier.” Intense, marathon interviews are part of the Morris process. In the end, the transcripts of all his taped interviews for “Standard Operating Procedure” totaled more than 1.5 million words. (The transcripts do double duty: They were also used in his book “Standard Operating Procedure,” co-written with Philip Gourevitch.)

As Karpinski spoke, she was sitting in front of a backdrop that had been painted to resemble a bare cinder-block wall. Morris began the interview (according to his film editor, Andy Grieve) with the same sentence he always opens with: “I don’t know where to start.”

Morris was looking Karpinski in the eye the entire time she spoke, but they were not in the same room. That’s because he uses a curious contraption he calls “the Interrotron” (it’s a term his wife, art historian Julia Sheehan, coined and that Morris embraces even though it “does sound like something from Flash Gordon”), which puts his face on a screen in front of his subject while he is in another room watching the subject on an identical screen. The Interrotron uses teleprompter technology that puts a camera lens behind the screen; the result is that the footage gathered has the interviewee staring straight into “the eye” of the audience, a subtle but powerful difference from traditional documentary footage that has the speaker looking at the person he or she is talking to, which means their gaze is a few degrees removed from the lens.

“Eye contact is one of the essential features of human communication; it’s hard-wired into our brains,” Morris said. “You know when I’m staring at you.”

The added intensity of the speaker looking into the eye of the audience is not the sole reason for the Interrotron. Morris admires the layer of space it creates, an electronic void between him and his subject. “I have a problem with this idea that intimacy and technology work at cross purposes,” he said. “I used to have this expression: Being there is the next best thing to being on the telephone. ... The Interrotron is like the telephone in a way — it excludes things. As a result it makes other things possible.”

Morris delights in the role of informed contrarian, and he especially enjoys the paradoxes he sees in the world around him. His dramatic reenactment footage, including almost otherworldly scenes inside the prison, may be criticized as false and bombastic, but he is absolutely certain that the scenes are the best way to find the texture of bigger truths. The crux of “Standard Operating Procedure” is also a contradiction: The photographs of grinning guards and degraded prisoners that outraged the world did not reveal “the real story,” as Morris puts it, or, in the words of one of the military subjects in the film, “When you see a picture, you don’t see outside the frame.”

The complicated message of “Standard Operating Procedure” is that the real crime was missed, that the “smoking gun” was the prison itself and that those punished in the wake of the scandal were bit players, offered up to the world as two-dimensional villains.

“I went into this movie looking at pictures, and I wanted to make a movie about walking into history through a picture,” Morris said. “Photography can lead us astray; we can be tricked by ocular proof. And photography — and I believe this is the right verb — can entice us into error. We’ve all seen the Abu Ghraib photos, but do we understand what they mean? Do we understand why they were taken? Do we know what is actually in those photos?” Later he added: “The movie is trying to defeat a view that almost everybody has. ... I’m telling a radically different story than the received story.”

The photographs from the prison showing ghastly images of torture and debasement were instantly politicized, Morris said. For liberals, they spoke to the nature of the misbegotten war and the role of the administration, while conservatives seized on the “few bad apples” story arc.

Morris, naturally, concluded both sides are wrong because they seized on the event as a political matter before they knew what they were looking at. “This is not a political event. Some kind of real investigation was needed.” What about the 13 government probes into the prison? Morris calls them “unreadable” exercises in futility due to government and military euphemisms, acronyms, double-speak and redactions. He’ll take his approach — a lone man with an Interrotron — any day. “I try to ferret out the story behind the morass of information. But it’s hard work.”

What’s next for Morris and his Interrotron? He has no interest in making traditional Hollywood fare. So instead it will be TV commercials, which he makes to pay the bills, and perhaps a film on a photograph he is enamored of that depicts thousands of eggs piled up on a South Pacific island in 1892. He had been searching to find which was photographed first, the chickens or the eggs, as a playful exercise, but the research led to a loopy, forgotten history of guano harvesting and wars over the smelly commerce. “I used to make funny movies, and I think of myself as a funny person, so maybe I’ll go in that direction.” Whatever he does next, heavy or light, will surely depend on the art of the interview.

“A friend of mine said you can’t really trust people who don’t talk a lot,” Morris said. “If people don’t talk, how can you know what they are thinking? I have been blessed by a lot of people who talk a lot.”