There are many contrasts and contradictions in the director Warwick Thornton’s new neo-western, Sweet Country. Its political messages are unsubtle, but the tone is meditative and the drama achingly personal.

Stunning cinematography captures vast outback landscapes but small details resonate: a chain dragging across dirt; a bullet hole in a wall. The themes are universal but the film is unmistakably Australian.

“It resonates in a strange way with people,” the director tells Guardian Australia. “It’s a classic tale. It’s about land grabs. It’s about taking over the country. It’s a basic western that people relate to on a range of different levels, based in a place they don’t have access to: 1920s central Australia.

“I don’t know exactly why, but it’s working very well around the globe. The really interesting one was last night’s screening.”

The night before our interview, Sweet Country made its Australian premiere at the 2017 Adelaide film festival – the first time local audiences had a chance to see the film, whose reputation preceded it.

The buzz began after Sweet Country won the special jury prize at the Venice film festival in September, then, one week later, received another prestigious award from the Toronto international film festival. But Adelaide was a particularly important screening for Thornton, because, he says, “The film is completely about Australia. It’s completely about who we are and where we come from.”

Like Thornton’s 2009 directorial debut, Samson and Delilah – a brutal portrait of poverty and addiction in contemporary Indigenous Australian communities – Sweet Country confronts difficult subjects head on. In this case, Australia’s dark past: what Thornton and his screenwriters David Tranter and Steven McGregor argue is a nation built on the back of slavery and racism.

This polemic is reflected through the story of Sam Kelly (Hamilton Morris), an Aboriginal man employed as “blackstock” by a kindly preacher (Sam Neill). Sam and his wife, Lizzie (Natassia Gorey Furber), are borrowed by the violent, bigoted Harry March (Ewen Leslie) who, one evening, in the throes of terror, Sam shoots dead. It is clear that if the shoe were on the other foot, Sam’s death would be swept under the rug, but Harry’s is certainly not – drawing any number of parallels to race-based double standards throughout Australian history.

“If we want to man up, or stand up as a country and move forward, we need to know about our history,” Thornton says. “The film is completely truthful about history, even though it’s fiction. I think Australia is really ready for films like this. We’ve got constitutional recognition, conversations about treaties.

“If you want to go into those conversations with better knowledge, it’s a good film to watch about Australia’s past.”

The Australian audience agreed, giving it a long standing ovation, then, a couple of weeks later, another gong to add to its tally: the best feature fiction prize from the festival’s audience awards.

Sweet Country was a family affair. Thornton, 47, worked closely with the second unit director and second unit director of photography, his son Dylan River. River became interested in film-making after the release of Samson and Delilah. He was 24 Sweet Country was shot.

“Because I’m his son, and I’m on set, I’ve got a different relationship with him than other crew,” River says. “If somebody had some question they knew was a bit touchy, they would ask me to ask it. Or they’d have an idea, and make me act like it was my idea.

“Sometimes the response was positive, other times he would growl at me and say, ‘Go away, you know I’m stressed.’”

The shoot was short – just 22 days – and the locations remote, in the picturesque MacDonnell Ranges of the Northern Territory. Filming struggled through extreme weather, including multiple floods. One day, according to Thornton, “We drove out of the set, 20km, with a metre of water over the bonnet.”

River believes their knowledge of the land was key to their success. “The thing that held this film together when we were shooting was the fact that we were in our home, Alice Springs,” he says.

The director agrees: “I had control over the cinematography because I grew up in that town. I knew where to shoot and I knew how to work the light. Even if we were shooting at 12 o’clock in the day, I’d design scenes that worked at that time, in that kind of light.”

Limited time and money meant “acknowledging the things you can’t control”, says River, “and turning them into blessings”. In a film widely praised for its visual aplomb, some of the most striking flourishes were happy accidents. A rainbow that appears at a crucial moment, for example, wasn’t planned for. Nor was one striking image of Bryan Brown (playing a cop in pursuit of the murderer) who, in one scene, desperately parched, finally finds water in the desert.

“There’s a funny, spirit kind of thing that goes into his face as he looks around,” Thornton says. “Water had splashed on the front element of the camera. Slowly it drained away and created this fractured light. We went, ‘This is awesome, let’s embrace it’ ... When he gets in the water it’s almost like his spirit comes back, the fractured light on the lens. It’s really beautiful.”

Being both director and cinematographer is an unusual combination, but one shared with another Indigenous film-maker, Ivan Sen, who directed Mystery Road and Goldstone. Thornton says “there should be more directors who shoot, I don’t know why there aren’t”, then perhaps goes on to answer his own question: juggling both duties is a challenge.

“There was a massive balance I had to play with on every scene, between how much I spent on cinematography and how much I spent on actually directing – getting the cameras in the right places, creating the style and form, directing the actors,” he says. “Some actors need a lot of nurturing. Others need to be pushed … There would be films where I’d be mad to shoot them, because if I did I would not be directing them properly.”

Adds River: “It was borderline. Even though Sweet Country looks beautiful, there were times when your shooting was getting in the way.” He describes moments when his father, time-strapped, asked him to take over camera duties so he could focus on the actors.

Thornton looks at his son, then responds: “Yeah, it was borderline. So next time you’ll be like, ‘Make me the DP,’” he says, laughing. “That’s what he’s up to, the little bastard.

“Well, that might happen. If you be nice to your father, you might get to shoot the next one.”

• Sweet Country is released nationally on Thursday