With his trademark manic stare and one eyebrow raised sky high, he looks both bewildered and amazed. But right now, Black isn’t playing for laughs. He’s trying to explain to a visitor the camera technology that allows him to play a hero who is a giant among tiny men and women. “It’s wild,” he says. “I’m, like, 12 times bigger than everyone else in the cast. But they’ve developed this, like, amazing camera, so I can be in the same shot as the little people and interacting with them.”

How does it work? Black’s eyebrows shoot even higher and he stretches out his arms in an eloquent “don’t ask me” expression. Here on the backlot of Pinewood Studios, some 20 miles west of London, various key elements for different scenes in “Gulliver’s Travels” are strategically placed at some distance from each other — a clear indication that this is a green-screen production, dependent on elaborate special effects to be inserted later.

Fifty yards from the main set of “Gulliver’s Travels,” in which he plays the title role, Jack Black is sprawling on a chair outside his large trailer, having assumed a facial expression familiar to those who know his big-screen work.

With his trademark manic stare and one eyebrow raised sky high, he looks both bewildered and amazed. But right now, Black isn’t playing for laughs. He’s trying to explain to a visitor the camera technology that allows him to play a hero who is a giant among tiny men and women. “It’s wild,” he says. “I’m, like, 12 times bigger than everyone else in the cast. But they’ve developed this, like, amazing camera, so I can be in the same shot as the little people and interacting with them.”

How does it work? Black’s eyebrows shoot even higher and he stretches out his arms in an eloquent “don’t ask me” expression. Here on the backlot of Pinewood Studios, some 20 miles west of London, various key elements for different scenes in “Gulliver’s Travels” are strategically placed at some distance from each other — a clear indication that this is a green-screen production, dependent on elaborate special effects to be inserted later.