When translating a hit stage production to the screen, it seems only right to retain at least some of the talent that made it a success in the first place – and not merely as a good-luck token. That’s a logic that frequently escapes Hollywood, as any number of Broadway ensembles replaced wholesale by bigger names can tell you.

When it came to Tony Briggs’s popular 2005 production “The Sapphires,” however, two cast members remained on board when the Australian musical comedy was translated to the big screen, though neither one in quite the same capacity. But while actress Deborah Mailman simply switched to a different role, Wayne Blair’s reassignment was rather more dramatic: he was selected to direct the film as his debut feature. In contrast to yesterday’s interviewee Chris O’Dowd, who read the script and hopped on board one month before shooting, Blair and Mailman each brought seven years of physical and emotional investment to this heartwarming, fact-based story of a female Aborginal soul quartet chasing the big time against the turmoil of the Vietnam war.

Speaking on the phone from New York, Blair explains that his involvement was the result of being “in the right place at the right time.” “I’m good friends with Tony, the writer,” he adds. “The play had been a sellout and he’d received a number of offers to make it into a film, so when he asked if I’d like to direct, I jumped at it. But I didn’t know when it was going to happen: that was around 2008 or 2009, so it was a bit of snowball effect. We get some money together at Cannes in 2010, and two years later, there we were on the red carpet at the premiere.”

Though he faced all the daunting challenges of any debut feature, Blair believes his background as an actor in the stage show gave him something of an advantage. “Having been in the belly of the beast, and knowing the heart and soul of the project, I guess that did give me a different perspective,” he says. “The screenplay is somewhat different from the stage show, so I knew the essence of the story and how it had grown. So it was a matter of conveying that essence to people who hadn’t been a part of it. And I like to think that going into directing from an acting background gives you a good sense of communication. It’s a bit of a process when you’re dealing with five lead actors every day, all of whom are coming to the story from different places.”

He had an ally, however, in his stage co-star Mailman, who took on the role of The Sapphires’ oldest and most fiercely protective member, Gail. The character actress, far more genial and soft-spoken than her feisty character, is also glad of her history with the material: “It was great coming to the film having been in the show – we had a real understanding of what this story, and these roles, demanded. But it’s shifted and expanded so much since those early 2005 performances, so it’s been a real privilege to see the full circle of this story. The journey’s been pretty amazing.”

Aside from practical alterations, including a rejigging of the show’s song list and switching the nationality of the male lead to suit O’Dowd – the character of Dave, the band’s zany but dedicated manager, went through English and Australian incarnations on the page before the Irishman landed the part – Blair explains that the most significant change made from the show was the deepening of the story’s social context. A subplot connecting the girls’ family history to the Stolen Generation of indigenous Australians alludes to many years of ingrained racial prejudice in the country, making the achievements of The Sapphires’ real-life inspiration all the more remarkable.

“Tony and Keith [Thompson, the film’s co-writer] decided they wanted to address the issue of the Stolen Generation directly in the film, so it definitely has a more political edge than the stage play,” Blair says. “It’s been interesting bringing the film to American audiences: they’ve taken an immediate interest in that angle, noting the correlation between the events in Australia and the civil rights movement. So it’s been great to see people connect to the story that way. More so than in any other country we’ve been to.”

For Mailman, of course, the chief challenge of the screen adaptation was adjusting to a new character: on stage, she’d played stroppy, fame-obsessed younger sister Cynthia, a very different creation from the more pragmatic, mature Gail. “It actually gave me a fresh perspective on all the characters,” she explains.

“Gail anchors the reality of these young girls’ world. Because you have these three girls who all want very different things for themselves – Cynthia wants to be famous, Julie just wants to perform, Kay wants to belong – while Gail’s main concern is keeping them together as a family. When I was playing Cynthia I was a fair bit younger myself, but now I’m the mother of two boys, so I connected to Gail’s mama-bear quality.”

Mailman didn’t walk into her role, either – auditions were extensive, as Blair and his team toured the country to find a quartet with just the right chemistry, eventually filling it out with golden-voiced Australian Idol runner-up Jessica Mauboy and new faces Miranda Tapsell and Shari Sebbens. “All the girls did five or six auditions,” the director recalls. “We wanted to unearth new talent, just as the four girls were discovered back in 1968, just by taking a chance. So that process was great in finding out just who these characters were: with that amount of auditions, the girls got to grips with their characters so much more.”

Mailman agrees that the audition period was crucial: “When we eventually got to the pre-production process, when is the director allowed that space for us to really bond together and be sisters? Thanks to the auditions, the relationship you see in the film is very much the relationship you’d have seen on set: we are family.” Blair chips in: “Yeah, we’re getting a bit like the Brady Bunch – we just had our New York premiere last night and all danced together. We’re just wondering when this ride will stop.”

The ride’s taken them pretty far already: in addition to the film’s domestic box-office triumph and sweep of the Australian Academy Awards, Blair was named one of Variety’s 10 International Directors to Watch last year. It’s an unparalleled success for an Australian production from an indigenous filmmaker, and with a substantially indigenous cast. Blair hopes it doesn’t remain so: “There’ve been about six or seven stories written and directed by indigenous filmmakers in the last hundred years, so it’s still a slow process,” he admits.

“Still, several of those have travelled the world – especially at Cannes, which has been something of a second home for indigenous cinema. So if we keep getting chances like these, great things will happen. This is a foot in the door.”

"The Sapphires" opens in US theaters today.