Always popular with the Academy voters, fully half of the contenders for best picture this year are historical dramas. Four of the eight films vying for the top prize — “Selma,” “The Imitation Game,” “The Theory of Everything” and “American Sniper” — are based on real people and their impact on the world in disciplines ranging from warfare and science to civil rights.

Several also explore the dark undertones of human nature — violence, persecution, discrimination — while some shine a light on the inspirational aspects of their subjects.

“There’s definitely a movement toward inspiring true stories,” says Anthony McCarten, a producer of “The Theory of Everything” who is also nominated for his adapted screenplay about astrophysicist Stephen Hawking. “The pressure you feel is to do it justice. The work has to be in service to the truth.”

Whether the stories are set decades ago or in recent years, filmmakers face challenges in re-creating history and telling real stories accurately while making judgment calls and taking artistic license to compress time and human relationships into a feature-length film.

Controversy often arises around pivotal characters that the films are based upon, as it has to some degree for nearly all these contenders, but that’s nothing new. Previous fact-based Oscar nominees, including “Zero Dark Thirty,” “A Beautiful Mind” and “The Hurricane,” have also aroused controversy about their subject matter or biographical content.

Andrew Young, who was a key player in the civil-rights struggle and is portrayed as the Rev. Martin Luther King Jr.’s top aide in “Selma,” has strong feelings about the film, starting with opening scenes in which four young girls are killed in a bombing at a Birmingham, Ala., church.

“When I first saw it, it knocked me off my feet. I had just sat down with popcorn when the girls came down the steps. I was visibly shaken up,” he says.

“Anybody that says the film totally and deliberately distorted the character of LBJ, I think he was portrayed very well. At the end, you see him confronting Gov. George Wallace, and making the speech about the Voting Rights Act of 1965,” says Young, who went on to become a congressman, ambassador to the U.N. and mayor of Atlanta. “There’s no way you can make a film and just have two simple do-gooders getting along and working this miracle of transforming the U.S. — it was just not that easy.”

While the civil-rights struggles of the 1960s have been well documented, the story of English mathematician Alan Turing was not previously addressed on the bigscreen — until “The Imitation Game” brought his saga to life. (Hugh Whitemore’s 1986 play “Breaking the Code” had previously depicted Turing’s story.) Spanning nearly 30 years, including scenes of Turing as a brilliant schoolboy who loses his best friend, the film focuses on his groundbreaking work building a machine to crack the Nazi Enigma code for the Allies during World War II and later his persecution as a gay man by the British government after the war. (Turing was one of about 49,000 homosexual men convicted of gross indecency under British law between 1885 and 1967.)

The idea for the film originated in 2009 when U.K. Prime Minister Gordon Brown issued a public apology to Turing, nearly 60 years after his death.

“Our greatest challenge was to capture his spirit, accomplishments and ultimately his character without making it feel like a laundry list without a sense of who he was. Intertwining three different time periods was the best way to do it justice,” says Teddy Schwarzman, one of the producers.

“There was no audio or video of Alan, which meant we had to put together the character from his own writings and other people’s accounts of him. But that worked out well for Benedict Cumberbatch; he couldn’t do an impression, he had to find Alan from the inside,” says screenwriter Graham Moore. He notes Cumberbatch wore prosthetic teeth in his portrayal of Turing.

Even with a limited $14 million budget, the film was produced on location in London. “Shooting at Sherborne, Alan’s actual school, and Bletchley Park, where he and his team actually worked, felt personally gratifying but, more importantly, gives the movie a sense of authenticity,” says producer Ido Ostrowsky.

“We credit Graham Moore, and our director, Morten Tyldum, for becoming single-mindedly obsessed with not only getting Alan Turing right, but researching every element of this story, from war history to computer theory, and beyond,” adds producer Nora Grossman.

“Everyone on the film knew from the beginning that this was going to be one of most important things in our lives,” says Moore. “If anyone’s story deserved a film, (Turing’s) did, and we wanted to do a film to make his legacy proud. There was a tremendous responsibility to tell it well.”

In “The Theory of Everything,” based on Jane Hawking’s memoir about her courtship and marriage to the esteemed astrophysicist after he developed ALS and was given just two years to live, the filmmakers received an unexpected gift. After approving the script, Hawking gave his real computerized voice to them, reading all of his lines of dialogue.

“Stephen had previously said he wasn’t interested in a movie that looked at his personal life, only at his scientific achievements, so this was like him hugging us,” says Lisa Bruce, one of the film’s producers. “People think the voice is generic, but it’s patented and copyrighted, and it gave the film a veracity we didn’t have prior to that.”

Before landing at Working Title, Bruce says other companies had suggested the film end when the couple were happily married and that the key roles be played by major stars so it could be pre-sold internationally.

“For Eddie and Felicity this was the perfect moment in their careers, and they hit it out of the park, but there was tons of pressure on them playing real people,” she says.

McCarten felt the pressure as well, working with Jane Hawking for eight years before obtaining the rights to her book.

“When you go into the intricacies of personal life, you’re relying on inspired speculation,” he says. “Ninety-eight percent of the dialogue invented by me is emotional ventriloquism. You hope you get it right, you hope when the subjects see it they’ll endorse it. Both declared it broadly true and a surprisingly honest portrayal of their marriage.”

“American Sniper” is another film that necessitated certain changes along the way. The script was initially based on Navy SEAL Chris Kyle’s autobiography, but two days after screenwriter Jason Hall, also an exec producer on the pic, turned in the first draft, Kyle was murdered, allegedly by a fellow Iraq War veteran he was trying to help. As a result, the film took on new dimensions as Hall spoke for hours on end, daily, for months with Kyle’s widow, Taya, and grieved with her.

“I was invested in the story of every soldier and what we ask of them when we send them to war,” says Hall, who had met extensively with Kyle and saw a humility in him that was not represented in the book.

“My struggle over the next years was knowing who he had been. This guy was someone else before he became a warrior, so for me it was about digging into his psyche and what it cost him.”

In addition to the Kyle family’s blessings, Hall says he is most touched by the outpouring of support from veterans and their families who have told him their personal stories of living with the aftermath of war.

“Taya bravely opened up and explained everything about this man, including the caring side,” says Hall. “She walked me through how the war had changed him and how the hardening and callousing of his character had affected him in such a profound way.”