Four West Australian feature films have made the shortlist for Australia's most lucrative film prize, CinefestOz.

Six films are in contention for the inaugural $100,000 prize, which is chosen by a jury of five film industry members headed by Australian director Bruce Beresford.

WA films Paper Planes, Son of a Gun, The Waler Australia's Great War Horse and The Reckoning are in the running, along with Victorian film Felony and My Mistress, which was filmed in Queensland.

The film festival is held in a variety of venues including wineries and galleries in WA's South West.

CinefestOZ vice chair Helen Shervington said she was overwhelmed with the quality of films, many having already received international attention.

"When we introduced this prize we anticipated a strong response, but the calibre of films has far exceeded our expectations," Ms Shervington said.

The only documentary to be a finalist, The Waler Australia's War Horse, premieres at the festival.

It tells the story of the 130,000 Australian horses that served in World War I.

Many of horse scenes were filmed on beaches in Lancelin, north of Perth.

Producer Marian Bartsch said 30 horses were used in the film, which took about a year to produce.

"We filmed interviews in outback WA as well as all over the country, plus footage in Istanbul and Israel in the areas that were parts of Palestine at the time of WW1," Ms Bartsch said.

The ABC will screen the film next year for the ANZAC centenary.

Crime thriller director says The Reckoning is the underdog

Crime thriller The Reckoning has already won Best Director at the British Independent Film Festival and the rights have been purchased by distributors for release in 40 countries.

The film stars Australian actors Jonathan LaPaglia and Luke Hemsworth and was filmed around the Perth suburbs of Applecross and Victoria Park as well as in Fremantle.

Director John V Soto describes his film as the underdog for the prize and says his budget of $2.3 million is one of smallest of the finalists selected.

Producer Deidre Kitcher, who is married to Soto, said WA's film funding agency ScreenWest had invested more in film than agencies elsewhere in Australia.

"We are honoured to be selected for such a prestigious prize and I think Western Australia is leading the way in feature film making," she said.

She said the locations and natural environment in WA made the state an unrivalled place to film.

"We recently had Chinese co-partners come visit the South-West for a Chinese film and they were amazed with the variety of places to shoot," she said.

Son of a Gun is directed by Julius Avery and stars Hollywood actor Ewan Macgregor.

The drama follows the story of a prison break and was partly filmed in the South West.

Paper Planes, directed by Robert Connolly, is about a WA boy's passion for flight and his challenge to compete in the World Paper Plane Championships in Japan.

The Waler will have its world premiere at CinefestOz while the festival will also host the Australian premieres of Son of a Gun and The Reckoning.

The winner will be announced at the festival on August 27.