Producers of the beloved ABC series had set up a goal of $250,000 to be reached in 30 days, to plug up "financing gaps" in the project and prove to investors that they "have a strong fanbase who will come out to watch the film".

That figure was smashed within the campaign's first 48 hours. Follow-up targets of $300,000 and $400,000 were reached within the next 24 hours.

With 25 days still left on the crowdfunding campaign, they've now upped their target to $500,000. It's currently already at $440,000 and counting.

"Oh, it's fantastic," creator Deb Cox told Fairfax Media. "We knew there was enthusiasm, and that our fans would be particularly motivated because we have such a strong following, but it's all a new language to me - we had no idea the response would be this strong."

Cox and fellow creator/producer Fiona Eagger say they'll use the additional funding to add new scenes to the film, increase the international filming days in their shooting schedule, and "add new costumes to Miss Fisher's wardrobe".

"With a television background, we're very used to faking it," Cox laughs. "We've shot Paris out of Melbourne... We're used to achieving a lot on a very limited budget. But this means there'll be those extra flourishes you want from a cinematic piece."

Rewards for the campaign's backers range from thank you postcards ($15), items from Miss Fisher's wardrobe ($2000), and spots as an extra on the film's set in Melbourne ($6000).

The TV series, based on the novels of Australian author Kerry Greenwood, has been a remarkable hit for the ABC, broadcast in 179 countries and screened on Netflix around the world.

It's become a cult fave thanks to its smart writing, stylish aesthetics and Essie Davis' popular leading turn, which has seen her nominated for an AACTA Award and two Gold Logies.

But Davis' recent career burst in London - including a stint on HBO's Game of Thrones, and Starz period drama The White Princess - had made the prospect of another lengthy series shoot impossible, leading to development of the film premise.

Eagger and Cox had revealed in November that scripts had been penned for an "Indiana Jones-inspired" movie trilogy. But the Kickstarter campaign describes the project as a "stand-alone theatrical release".

Titled Miss Fisher and the Crypt of Tears, the movie is set to take place following the events of season three, with Phryne taking off on "a global adventure - via romantic wayside stops in the Far East, glamorous sojourns in the mansions of London, and a battle to survive the rolling sands of the Arabian desert," the Kickstarter notes.

With such fan enthusiasm and Davis' confirmed involvement, why was the show forced to turn to crowdfunding for its big-screen adaptation? It's complicated, says Cox.

"Financing for a film is very difficult in Australia. You need your local distributor, an international distributor, you also need support from Screen Australia and whatever local bodies... It's often an incredibly complex patchwork quilt," she explains.

"Obviously the budget for the whole film is going to be a lot more, but this means we can do extra things we might not have thought we could afford, like go to those real locations."

Morocco, Israel and London are already being considered as new shooting spots, according to the film's Kickstarter page.

"More importantly," Cox added, "it shows that the fans want the film, they're behind it, and there's an audience for it... It's a little bit chicken and egg, it helps us get all the other pieces in place. The fans are doing more than just giving us a bit of extra money; they're actually helping the whole thing happen."

Besides the film, a previously flagged spinoff, focusing on a young Phryne Fisher, is also in the works for the ABC, Cox confirmed.

"Yes, we've been developing that. We'd like to expand the world and do a kind of origin story, the making of Phryne Fisher," she says.

"It would be set in the First World War. It's not about the war, the Anzacs and that, but really about the home front - what the domestic politics were, and what life was like for women during the war."

The concept, said Cox, was inspired by the show's ever-increasing younger demographic.

"I remember meeting these two young women and they said, 'We love Phryne because she's glamorous, and she can do whatever she wants, and she has a man whenever she wants - but she's not Miley Cyrus!' (laughs). I finally understood what they liked about her. The fact that she's this modern woman, but also quite refined.

"I think it started as an intergenerational thing, with young people watching with their mothers and grandmothers. But we want to create something they can identify with more strongly," she says.

The film is planned to begin production in May 2018, for a theatrical release in mid-2019.