Conventions of a Documentary

Actuality 

This is the term used for raw film footage of factual and existing events as opposed to dramatized ones.

Voice Over

Commentary by the filmmaker spoken over footage for exposition or information.

This example opens with Voice Over to give a brief overview of what the documentary is about.

Direct and Indirect Interviews

Interviews allow people to speak about events with the prompt of a question, The interview may be on or off screen, possibly with a set. Interview segments are merely clips from a longer interview, addressing relevant issues and topics in the documentary. This helps add a sense of realism to the documentary as well as an opinion to consider or share for the viewer.

This example uses both, with a set for an interview as well as clips of relevant topics played over the dialogue:

Archival Footage

This is footage from an archive or film library inserted into a documentary to show historical events, or add detail without the need for extra filming.

This example has a voice over of archival footage of trains and railroads.

Reenactment

This is a dramatization of an event, acted out so that the viewer can see the event and better understand it even though the cameras did not film it. Reenactment is often indicated through visual effects or a disclaimer.

Montage Sequence

This conveys ideas through a visual order of shots in the film.Narrative montages involve planning of a sequence of shots used to indicate changes in time and place within a film. Ideational montages link actions with words. Montages are usually linked to words characters say. This visual representation makes it easier for the viewer to understand and retain the information being given.

Exposition

This occurs at the beginning of a film and introduces important themes. This is vital as it creates the audience's first impression of the film.

This example opens up with exposition, both in text form and through recorded audio from the event.