If you’ve ever stood in front of a J.M.W. Turner painting, there’s a good chance you’ve been swept away by the lush watercolor and gorgeous landscapes.

You might be surprised, then, to encounter the artist as portrayed in Mike Leigh’s “Mr. Turner,” which opens in theaters Friday. As portrayed by Timothy Spall, he’s gruff and unpleasant with a messy personal life. The film illuminates and gives equal weight to both sides of the icon, with a visual approach that replicates the look of Turner’s paintings and a character-driven focus that undercuts any mythologizing.

“He is a cinematic painter,” says Leigh, 71. “How the hell he does it remains a mystery. He is cinematic. That was a starting point. I thought, ‘Well, maybe there’s a film in it.’ I thought that after we made ‘Topsy Turvy.’ And then I started to research the personality of the man, the character and the tension between this complicated guy and this epic stuff. It’s fascinating really.”

Leigh, one of the great filmmakers and an unparalleled modern voice when it comes to cinematic realism, says the approach is consistent with a career of more than four decades that has encompassed accomplished works such as “Secrets & Lies” and “Vera Drake.”

“The idea that an artist is a grubby, practical engineer who rolls up his sleeves and gets down to the down and dirty business of manufacturing this commodity is something that people don’t think about,” Leigh says. “What I’m always persistent about, and you’re familiar with all my films I dare say, is to look at people as we are, in terms of what the human experience really is.”

“Mr. Turner” marks the seventh time Leigh has collaborated with Spall, and the star says it’s precisely that focus on who we are and what life is like that keeps bringing him back to the director.

“He’s very, very interested in how human beings behave,” notes Spall, 57, who says Leigh first approached him about this project when they ran into each other on the street in London, and took years of painting lessons. “He’s interested in how they behave; really how they behave. He’s interested as much in the mundane and the everyday of human life as he is about any of the heroics of it.”

Leigh’s approach, which places a significant premium on improvisation and performance, has netted his stars considerable acclaim. “Mr. Turner” is no exception, as Spall took home Best Actor at the Cannes Film Festival and earned top prize from the New York Film Critics Circle earlier this month.

“My mom’s old,” Spall says. “Nice to be able to phone up your mom and say, ‘Your son’s just won an award.’”

While no one makes movies for awards or critics, Leigh is thrilled any time one of his collaborations with actors from his ensemble of frequent stars receives this sort of attention.

“For me it’s just a joy and it’s great,” Leigh says. “Because what we do is syncretic. We’re not just doing regular roles. It’s a different kind of acting. ... For it to be appreciated and understood and acclaimed in the mainstream is, to me, very exciting and rewarding.”