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Movies operate differently from plays. Tracy Letts knows and appreciates this point. There are things that the new film of “August: Osage County” can do that his Pulitzer Prize- and Tony Award-winning play, which premiered at the Steppenwolf Theatre in 2007, cannot.

For one, the John Wells-directed movie actually can let audiences see Osage County, the stark Oklahoma landscape where this searing, darkly humorous, multigenerational tale, inspired by Letts’ family history in the state, takes place. “I loved being able to show Oklahoma and show the expanse of it,” the 48-year-old writer-actor says over a club soda at a downtown luxury hotel, just a couple of miles from where he and his wife of several months, his Steppenwolf and Broadway “Who’s Afraid of Virginia Woolf” co-star Carrie Coon, live. “So the movie gave us opportunities.”

But movies have different requirements as well. When an extended family argues around a dining room table onstage, an audience member can choose when to watch the main combatants and when to glance at the others’ reactions. On the screen, the director is directing your eyes: Here’s Meryl Streep’s brutal Violet making some merciless remark, and cut to Ewan McGregor’s aghast Bill or Juliette Lewis’ disconnected Karen.

Also, the stage “August” ran 31/2 hours, including two intermissions, while the movie — which opens Jan. 10 in Chicago — is two hours long. As the Steppenwolf ensemble member approached adapting his work for the screen, some changes felt organic. For example, the play’s prologue is a 15-minute conversation largely between Beverly (the patriarch originally played in Chicago and on Broadway by Dennis Letts, Tracy’s late father, and on screen by playwright-actor Sam Shepard) and Johnna, the Native American housekeeper he is hiring (Kimberly Guerrero onstage, Misty Upham on screen).

“You can’t start a movie with a 15-minute static scene between two characters who are not your central characters,” Letts said. “Well, you could, but it’s not going to be a movie that’s playing on Dec. 25.”

So Letts tightened up that intro — but that’s not to say he wouldn’t have preferred a longer “August” than the one in the movie. With a play, the writer reigns supreme. With a movie, particularly one involving much high-profile talent, the writer is just one of many voices in the room.

In this case, you had Wells — who has overseen such TV series as “ER,” “The West Wing” (for its final three seasons), “Southland” and “Shameless” — plus producers who’d taken the play to Broadway and thus controlled the material (among them Jean Doumanian, Steve Traxler and Harvey Weinstein with the Weinstein Co., which is also releasing the film) and additional producers George Clooney and Grant Heslov. A-list stars, specifically Streep and Julia Roberts, also were involved.

“There are a lot of people whose opinions need to be listened to,” Letts said.

Letts said his first screenplay draft ran 200 pages long, and though he knew it needed a haircut, he then bristled at the suggestion that length was an issue.

“I was mad at that point, saying, ‘Well, look, I’m going to cut this because it needs to be cut, because I recognize that it’s too long, but if you’re looking for an hour-and-40-minute movie that’s going to play on an airplane, I don’t know why the f— you got into the ‘August: Osage County’ business. You all saw the play. You’re the producers of the play,'” Letts recalled. “That was a fight that continued for some time until John came into the process.”

When Wells was hired, Letts said, the conversation changed. “It became a question of ‘Let’s approach this more thoughtfully. Let’s not talk about this in terms of page count or minutes. Let’s talk about this in terms of how can we tell the story through pictures? Where are the places that pictures suffice?'”

Wells, 57, said on the phone from London during a promotional visit: “So much of what has to be conveyed in the theater is all done with words, and then cinema is a visual medium, but you don’t want to lose the beauty and the majesty of Tracy’s words, which are wonderful. A lot of the conversation in the early going was just about ‘What are we going to see that onstage you had to describe?'”

The next issue, Wells adds, was “how close you are to the person. In the theater you’re 50, 100 feet away, so a lot of the facial nuance has to be conveyed through words, whereas we were going to be right on the actors and on the characters the whole time, so we were going to understand a lot of that subtext and a lot of what was going on between the characters.”

Letts said he was happy to engage in those discussions — and to stick up for his opinions.

“I fought for a lot,” Letts said. “I viewed that as my job. And John, being a guy who is the executive producer of television shows and has run writers rooms, he’s not a defensive guy. I was able to fight with John, and John could sit there and take it. We could fight with each other. Those fights are valuable.”

“I completely agree,” Wells said. “That’s actually where I think the best work comes from.”

One fight Letts said he won — though this one wasn’t specifically with Wells — was over the casting of Violet’s three daughters, all in their 40s in the play.

“There was a chance at one point that the sisters were going to skew much younger, and I was absolutely against that,” Letts said. “I said if we’re going to tell people that 30-year-old women know the same thing 40-year-old people know, we’re going to piss a lot of people off, and rightfully so.”

As it happens, Roberts (Barbara), Julianne Nicholson (Ivy) and Lewis (Karen) are almost spot on with the ages specified in the published play.

A fight that didn’t go Letts’ way was over interactions between 14-year-old Jean (Abigail Breslin) and Johnna in which the girl is smoking pot and discussing her parents’ fractured marriage. “That’s a scene that was shot and got cut, and I loved the scene,” Letts said, noting that Wells wasn’t happy with his direction of the scene but also that they’d been receiving notes from the higher-ups regarding the film’s pacing. “That pissed me off, so I fought really hard to get that scene back in. I was like, we never got any f—in’ pace notes when it was 31/2 hours long. Why are we having to listen to pace notes?”

“I miss it too,” Wells said of the scene, but he notes that when it was in the movie, early audiences indicated impatience. “Some of that is weight of having movie stars in other parts: ‘Why am I spending time with these characters when I really want to be seeing who I know are supposed to be the important characters because they’re being played by the movie stars?'”

Letts ultimately considers the two-hour running time to be “short for ‘August: Osage County.’ There’s an alternate-universe version of this movie which is two hours and 40 minutes long and a different kind of film and probably not very starry — right? — and certainly a different experience in the theater. But that’s not the version that we made.”

Likewise, he said casting anyone from the original Steppenwolf cast — including Tony winners Deanna Dunagan (Violet) and Rondi Reed (Violet’s sister, Mattie Fae) and Tony nominee Amy Morton (Barbara) — was out of his hands and out of the question.

“Would I have liked to have seen the Steppenwolf people given an opportunity to do it? Absolutely,” he said. “They were amazing. Everybody who saw them knows how amazing they were. But that’s not the way it goes, and I have to say from the earliest days when people would say to that cast, ‘I hope you get a chance to do the movie,’ they would laugh in their faces and say, ‘I’m not doing the f—ing movie.’ There are considerations of the marketplace to be taken into account. Always have been.”

Yet Letts stressed that his candor over some issues isn’t meant to signal an overall dislike of the film. “Don’t misunderstand me; I’m fond of the movie,” he said. “I think the movie’s great. It’s a different experience than the play, and I’m reconciled to that. If I had shot it word for word what the play was, it was never going to function in the same way the play did.”

Wells said he has no problem with Letts expressing his concerns. “I think people understand, and certainly sophisticated film audiences understand, that there’s a lengthy artistic process to try to arrive at what everyone hopes is the best version and that ultimately you’re not all going to agree on exactly what that best version is,” the director said.

To Letts, the most important point may simply be that someone like himself, who was raised in a small town, may now be able to connect to this very personal work.

“Where I grew up, my access to the great plays, great dramatized literature, was through movies,” he said. “In Durant, Okla., I wasn’t going to have an opportunity to see great productions of ‘Streetcar Named Desire’ or Shakespeare.”

So when his friends and fellow playwrights Martin McDonagh and Bruce Norris argue against having their plays adapted for the cinema, Letts — whose earlier plays “Killer Joe” and “Bug” previously were made into films by William Friedkin (“The French Connection”) — takes the opposite tack.

“What I say to those guys is, ‘But there’s some kid somewhere in some small town who’s not going to get access to great productions of ‘August: Osage County,'” Letts said. “His access to it is going to come through this movie.”

Since Letts collected all those awards for the stage “August,” his acting career has taken off. He won a 2013 leading actor Tony for “Who’s Afraid of Virginia Woolf” and landed the key role of a committee-chairing senator on the Showtime series “Homeland.”

“Writing absolutely surpassed my acting for a long time,” Letts said, “but now acting’s catching up a little bit.”

He starts rehearsals this month for the Broadway production of Will Eno’s “The Realistic Jones,” in which he’ll co-star with Toni Collette, Michael C. Hall and Marisa Tomei; he performed in the play’s 2012 premiere at the Yale Repertory Theater.

Back on the writing side, Letts is working on another film adaptation — of John Steinbeck’s “The Grapes of Wrath” for producer Steven Spielberg — and said he has a new play, “The Scavenger’s Daughter,” for which he’s seeking a home.

“I don’t think it’s going to be at Steppenwolf. It’s a big, unwieldy show, and it’s very expensive, and there are a lot of people in it,” he said, noting that it covers 40 characters over 90 minutes. “It’s a very strange play that nobody’s ever going to make a movie of.”

He said he has no plan for how he’ll juggle his various interests — “all of it is stuff I love to do” — but he and Coons have decided at least to remain in Chicago for now.

“Work keeps pulling us to the coasts, a lot, which means a lot of travel, and it’s a drag, and so we talk every day about our living situation,” he said. “And at the end of every day, we say, ‘We like Chicago, we like our house, we like it here.'”

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