Where do you draw the line when a movie is based on a true story?

It’s a tough question for every filmgoer to answer, and it’s different with every movie. One notion however, is clear: There is a certain perspective and level of expectation when you are led to believe that the film you are watching has some sort of basis in fact.

There are two main ways a story can betray your trust: First, the tiniest of falsehoods can set you off, especially if you are familiar with the story and know what actually happened. This is not a deal-killer, though, because smart moviegoers understand timelines are often compressed and composite characters are sometimes created to tell the story efficiently in two hours. A successful “true story” retains the overall theme of its subject without losing sight of it completely.

But secondly — and far more importantly — a story feels false when it loses the “ring of truth.” This is not just about betraying facts, because a movie can lose the ring of truth even if you have no idea what the true story it’s based on is about. The moment that credulity is stretched too thin by an overly convenient plot device or unmotivated action, the ring of truth disappears. This is a problem in all movies, not just the ones that purport to be based on a true story. But it is especially tough for those that say they are based in fact.

“Our Brand is Crisis,” starring Sandra Bullock as political strategist Jane Bodine, has this problem. What’s unique about this film is that it might have worked better if it never claimed to be based on a true story. As it is, the opening credits say it is “suggested” by the documentary “Our Brand is Crisis,” which was released in 2006 and followed Clinton strategist James Carville to Bolivia to help re-elect an unpopular president.

What sinks the movie isn’t that Jane is a completely fictional character or that Billy Bob Thornton plays an equally fictional rival (who looks and talks just like Carville), it’s that director David Gordon Green can’t find a consistent tone or point of view. “Our Brand is Crisis” wants to be a satire on the cynical, manipulative world of campaign strategy, but it also wants us to sympathize with Jane and get caught up in winning.

Rooting for Jane and her U.S.-led team of operatives means doing so at the expense of the Bolivians, who get a small amount of representation in the form of an idealistic young staffer, played by Reynaldo Pacheco. The actor is fine, but Peter Straughan‘s script does him no favors, reducing his motivation to a single childhood photo that meant a lot to his father. It’s responsible, of course, to include the perspective of Bolivians in the movie, but the movie never goes deep enough with any of them to make a difference.

Instead of getting a black comedy about powerful U.S.-government employed parasites pulling dirty tricks on foreign soil, we get a silly revenge story about two rivals who are supposed to be really smart — something we rarely see. This element of the story doesn’t have the ring of truth and neither does Jane’s late-in-the-game conscience development. It’s all too hard to swallow, and it might have worked better with a harder-edged tone, seeing as how this is some seriously nasty business.

“Steve Jobs,” starring Michael Fassbender as the titular technology icon, has an interesting problem with the ring of truth. Screenwriter Aaron Sorkin adapted the movie from Walter Isaacson‘s nonfiction biography, but then he also concocted a narrative strategy that by its very nature is fictional: He rearranged the people, the events, and the key confrontations in Jobs’ life in order to fit them into a stagey three-act play that takes place backstage in the minutes before three of his famous product announcements.

Apple co-founder Steve Wozniak, for example, may not have asked Jobs specifically to give a shout-out to the engineers of the Apple II (as Seth Rogen does playing Woz in the movie) but that request was made often, and it came from other engineers.

As stagey as “Steve Jobs” is, it burns with the ring of truth. The actors bring Sorkin’s highly stylized and biting words to vivid life, and it resonates on a human level. “Steve Jobs” is less about technology and more about the drive to succeed — the personal cost of passion, dedication to work, and pig-headed single-mindedness. Critics of Sorkin’s Jobs say the real man wasn’t like that — at least all of the time.

Sorkin plays fast and loose with the facts, But so did Shakespeare when he wrote “Julius Caesar” or “Henry V” or “Richard III.” I’m not comparing Sorkin’s prose with the Bard’s, but using a widely known and culturally important figure as a way into telling stories with universal themes is, well, universal.

Meanwhile, the movie “Truth,” playing now at Liberty Hall, has that slippery word right there in the title. The film features Robert Redford as longtime newsman Dan Rather and Cate Blanchett as his CBS producer, fired for airing a report based on forged documents. I haven’t viewed the film yet, so its truthiness remains to be seen.

One thing is for certain, though: As we consume media faster and more voraciously than ever before, the nature of a “true story” and how we perceive it will continue to evolve.