Like a sudden change in the weather, actors who have been quietly plying their craft can suddenly appear in view and make a loud impact.

James Stewart had been punching his Hollywood clock reliably until he hit with a flurry in 1938-39 with “You Can’t Take It With You,” “Destry Rides Again” and “Mr. Smith Goes to Washington.” Suddenly, he was everywhere, as was Humphrey Bogart when he finally landed his first starring role in “High Sierra,” or Paul Newman with “Hud” or Jessica Lange after “All That Jazz.”

It doesn’t happen all the time but it is this year, with two actors: Jessica Chastain and Michael Fassbender, starring in or featured in no fewer than nine films. What separates the two (she’s American, he’s Irish-German; she’s a porcelain-skinned beauty; he exudes a just-formed roughness, a swarthy danger) is less interesting than what unites them.

They both take charge of the screen when they enter, drawing the viewer’s attention like magnets. They lose themselves in their roles to an uncommon degree. Those who’ve seen Chastain as concerned wife Elizabeth in Jeff Nichols’ “Take Shelter” and then watch “The Help,” in which she stands out in a vibrant female ensemble as ditzy blonde Celia, can’t believe that it’s the same thesp. The actor who starved himself in Steve McQueen’s “Hunger” two years ago, that’s the same guy looking ripped and Adonis-like in the director’s “Shame”?

Range is what serious actors strive for, but they’re more likely to get it in the theater than the movies. While both Fassbender and Chastain do legit, their combined roster of extraordinary roles in 2011 would make a repertory theater actor blush.

As a contentious Carl Jung to Viggo Mortensen’s Sigmund Freud in David Cronenberg’s “A Dangerous Method,” Fassbender invests a man better known for his techniques with surprising vulnerability and carnality. In “Jane Eyre,” his Rochester registers as more dynamic than previous screen portrayals, while his sexually adventurous and emotionally desperate Brandon in “Shame” is a study of a man caving himself from within, until he has nothing left.

For more proof of range, consider that Fassbender cut quite a figure as Magneto in “X-Men: First Class.”

The sheer amount of work is dizzying to contemplate, and Fassbender confirms that his schedule was perhaps enough to wear out Magneto.

“I was incredibly busy to the point of exhaustion,” he says. “I worked for 20 months straight pretty much shooting films back to back, so it’s nice now to take a break and look for the next thing to do.”

Jumping between roles for Fassbender also means experiencing different directors and their methods — for instance, between Scott and McQueen, whose filmmaking approaches share at least one thing in common: “It was an amazing experience, but the interesting thing is how similar Ridley’s working environment is to Steven’s. It’s a very comfortable environment, and everyone is working hard and you don’t also see that on every set.”

The only complaint about Chastain to be heard lately is that she’s being seen in too many films at once. This makes her laugh (“It wasn’t planned that these many films would come out within a few months of each other!”), but it illustrates how many filmmakers wish to work with her.

Besides, the time compression of the releases doesn’t match their respective production skeds: For example, Terrence Malick shot “The Tree of Life,” in which Chastain plays the loving mother of boys growing up in 1950s Texas, three years ago.

Chastain jumped from “Shelter” directly into “The Help,” having to add 15 pounds for Celia, a woman who she decided “had to be played big, because Celia lives her life that way in order not to confront reality and the extreme poverty she’s run away from.”

But Chastain says it’s not always about the roles and prep. Her decision to take on the supporting role of Virgilia, peace-loving wife to Ralph Fiennes’ military hero-turned-traitor in “Coriolanus,” was largely motivated “by having a chance to be in a room and watch Vanessa Redgrave and Ralph Fiennes prepare their performances and learn from them.

“It was like a master class,” Chastain adds, “and I wasn’t going to miss that for the world.”

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