TORONTO -- Director David Dobkin is known for rollicking comedies including "Wedding Crashers" and "The Change-Up," but says the father-son legal drama "The Judge" -- which will open the Toronto International Film Festival on Thursday -- was the most enjoyable movie-making experience of his career.

"I hadn't had an opportunity to really dig in and do something like this in 20 years," Dobkin said in a recent telephone interview from Los Angeles, adding that his initial training at New York University was in acting and performance. "There are a lot of intense scenes in the movie. You would think that comedies are more fun to work on and they're not always as fun as they come out. This movie was strangely cathartic."

"The Judge" stars Robert Downey Jr. as a brash Chicago lawyer who comes home to Indiana for his mother's funeral and ends up staying on when his ailling father -- a respected local magistrate (Robert Duvall) -- is accused of a crime. He also reconnects with his two brothers (Vincent D'Onofrio, Jeremy Strong) and high-school girlfriend (Vera Farmiga).

Amid a cinematic landscape littered with tentpole franchises, goofy comedies and ultra-dark fare, the film feels like a throwback of sorts. Dobkin says that's no accident.

"I've always loved a lot of the dramas of the '70s that I grew up around, early '80s. I always wanted to make a movie like that, in the world of 'Kramer vs Kramer,' 'The Verdict,"' said the movie-maker, who is a co-producer on the film, along with David Gambino and Susan Downey.

"It was really nice to be able to work on it and really make it about performers and actors. Plus it was a very personal story and it was about realizing that moment in life when your parent needs you to be a parent and how you step into those shoes and how complicated and difficult that can be. And unexpected."

Rounding out the blue-chip cast are Billy Bob Thornton, Dax Shepard, Ken Howard and Leighton Meester. At the heart of "The Judge," however, is the thorny relationship between the father and son played by Downey and Duvall, who worked together on 1998's "The Gingerbread Man" and 2007's "Lucky You."

Asked whether two such decorated actors needed much direction, Dobkin said: "You've got to be in there with them and really moulding the vision of the work and making specifically sure that they're working totally together. It felt very comfortable to me. It was really fun. I turned to Downey and said: 'This is the most enjoyable movie I've made.' ... It was really a thrill."

When directing a comedy, the director said, there's "another ball that you're juggling" but with "The Judge" "the goal was a little more specific, a little more laser targeted."

The opening night slot at the Toronto International Film Festival can be a tricky one. For a long stretch, the movie marathon tended to choose homegrown curtain-raisers, like Jeremy Podeswa's holocaust drama "Fugitive Pieces" in 2007, the Paul Gross epic "Passchendaele" in 2008 and the hockey comedy "Score: A Hockey Musical" in 2010. But it's gone international in recent years, last year selecting the WikiLeaks drama "The Fifth Estate," in 2012 picking the twisty thriller "Looper" and in 2011 the U2 documentary "From the Sky Down."

In the past, organizers have said they want the opener to have broad appeal, since all kinds of film-lovers come to the kick-off screening. Many directors, however, instead have their eye on the heavyweight opening weekend.

Dobkin sees no downside whatsoever to showcasing his film on the first night.

"Oh my God we're totally thrilled. First of all, I love Toronto. My first movie was there 15 years ago," he said. "We love being (the opener). Things I love about the Toronto International Film Festival, specifically, is that it is an audience-driven festival of people who are movie lovers. It's not snooty and it's really approachable and fun and there's a 'joie de vivre' that I love about it."

"The Judge" has already screened to test audiences and he's confident festival-goers will like it, which helps lessen any opening-night jitters.

Said Dobkin: "I'm just looking for people to enjoy it and have a really good time ... we know that people love the movie so we don't feel a lot of pressure in that way."

The Toronto International Film Festival opens Thursday and runs until Sept. 14. "The Judge" is set to hit theatres Oct. 10.