Director and producer Jean-Philippe Tremblay, who spoke to The Canberra Times from Cuba on Friday, said the film aimed to raise questions about media ownership in every democratic country, but focused on stories from the US media landscape.

''We have really focused on the media monopolies held by five media conglomerates - News Corp, Time-Warner, Disney, Viacom and General Electric - and they dominate most of the media in the US and a lot of the media in the entire world,'' he said.

''And not only do they have holdings in media but they have holdings in all sorts of other businesses as well. General Electric has defence contracts, they make washing machines and light bulbs, and they have made nuclear bombs.''

Tremblay said 37 journalists featured in the film, including Pulitzer Prize winners.

''These journalists are out to report on power, whether it is government or corporations or the corporations they work for, and once the research or the report is written or at a very advanced stage they are stopped,'' he said.

''We asked the question: why are they stopped?''

Tremblay said his documentary also dealt with the high price journalists paid, including with their lives, for reporting difficult truths.

''There is also a sort of self-censorship culture happening in mainstream journalism,'' he said.

''If a journalist is faced with writing or reporting a certain kind of story they will think what the story means and how it can affect their career, their family, because there is a history of journalists being taken out.

''Governments understand the power of journalists and journalism and that's why they made it a pillar of our democracy [in the US constitution], and when journalists are doing their work and exposing corruption and showing it to the people - it's happened in war after war - one of the first targets is journalists and journalism institutions.''

Tremblay said his film also examined the role of the spin doctors employed by governments and large corporations to push positive stories into the media.

The screening of Shadows of Liberty, at the National Film and Sound Archive's Arc Cinema from 2.15pm, will be followed by a panel discussion.