LOS ANGELES: He is already Hollywood's highest-paid actor. Now Robert Downey Junior is increasing his Tinseltown heft by branching out into production as well as a serious dramatic role, in his latest movie.

In "The Judge" -- which contains parallels with the "Iron Man" actor's own redemption of recent years -- he plays a lawyer who returns to his home town to bury his mother, only to find himself in confrontation with his father.

Attorney Hank Palmer's relations with his dad, a well-respected conservative judge in a small town (played 83-year-old Robert Duvall), have been frosty for years, and don't improve despite the family reunion.

Duvall's character Joseph Palmer is "a grounded rock of a man," while Downey Jr's "is this boxer that's dancing like a butterfly around him trying to get his attention, his acceptance," said director and co-producer David Dobkin.

"He's refusing to give it and is judging him the whole time," he told journalists ahead of the movie's release this coming Friday.

Old wounds are re-opened but old relations also renewed as the ageing judge is accused of murder, and his ace lawyer son is forced to come to his rescue in the courtroom.

“There is something so repressed about these too men, their issues with one another, their history and admitting their own faults,” said Dobkin, known for lighter movies including 2013's Jack the Giant Slayer.

Story of redemption

For Duvall, his character “is very tough on his son, but ... tough can go hand in hand with love. Throughout the world families can be difficult,” he said. “I don't know of any family that's not complex,” added the actor.

With piercing eyes and fine features the actor is well known for hard-man roles and being one of Francis Ford Coppola's favourites, in films including The Godfather 1 and 2, and Apocalypse Now.

He won an Oscar for 1983's Tender Mercies among other honours, and has been making films for more than five decades with greats including Roland Joffe, Robert Altman and George Lucas.

Duvall voiced respect for Downey Jr., calling him "a very talented guy, very accessible and democratic .. different from a lot of big stars I've come across in my career."

The Judge recounts a father's redemption which mirrors Downey Jr's own path to forgiveness: the star, son of a filmmaker and actress, acted from the age of 5 but drug addiction nearly cost him his career, and more.

Thrown off the TV series Ally McBeal -- a show which saw him earn a Golden Globe -- in 1997, Downey Jr spent several terms behind bars, before emerging cleaned-up in 2003.

His return was spectacular, winning another Golden Globe for Sherlock Holmes (2009) and becoming Tinseltown's top-earning actor with films like the Iron Man and Avengers Marvel franchises.

He made $75 million just in the last 15 months or so, and his fortune is estimated at $170 million.

On his new role as executive producer of The Judge, the 49-year-old quipped: “You just have to be nicer. You can't produce a movie and just think about Hank,” he said.

“You want to keep a bunch of people who are away from their families, maybe not happy but looked after,” he added. "I'm used to saying 'Here's what I need'."

In a film in which Duvall's character is thinking a lot about his legacy, Downey Jr jokes about his own. “I'm almost 50 but I feel I'm just starting to grow a little bit,” he said.

“So I'll have to get back to you on that,” he said.