Part 3

So, for example, Robert Flaherty’s pioneering 1922 film Nanook of The North features scenes in which the Inuit family, which is its focus, hunt and catch a walrus. To catch this ‘authentic’ tradition, Flaherty actually required the family to re-enact a practice that had long gone out of fashion. In the same film, scenes shot inside an igloo necessitated the building of a special set with a wall removed so that the cumbersome camera equipment could be accommodated.
Another Flaherty film called Man of Aran (1934), told the tale of people living off the coast of Ireland and showed a shark hunt. Again, this was a practice that was almost extinct and an expert had to be brought in to teach the locals how to do it, before the cameras started rolling.

Another early documentary-maker was called John Grierson and sequences from his 1929 film Drifters about the herring fishermen of the North Sea required the redesign of the herring boat cabins, again so the bulky cameras of the period could be accommodated. So the search for truth has often involved documentary-makers in subterfuge and re-enactment.

There is no one way of telling a story using documentary, but there are different ways of addressing the subject matter and the audience. As has already been addressed, documentaries have often attempted to obscure the fact that they are highly constructed products, resulting from the rendering down of hours of film and the employment of careful film and sound editing. Think of specific examples you are familiar with where this occurs.
Expository
A very traditional form of documentary in which an unseen speaker performs a voiced-over commentary that literally explains the images that we are seeing. It is the form often associated with wild life or historic documentaries, in which the viewer might feel in need of information about what they are seeing. The audience is not particularly ‘empowered’ by this kind of approach, finding itself in a subordinate role listening to the version of events that the filmmakers choose to prioritise.
Observational
This is the mode associated with ‘fly-on-the-wall’ type documentaries. They appear to have been filmed in ‘real time’, as if the camera has happened upon events while those involved are seemingly unaware of the filming going on. The filmmakers correspondingly attempt not to interfere in what is underway. We do not hear their questions and we do not see them. There is no voice-over telling us what to think or what conclusions we should draw.
Interactive
Many documentaries feature a certain amount of interactive mode filmmaking. Such sequences will involve those being filmed responding to questions asked of them. In such interviews, the questions of the filmmaker may be left in or edited out. This may be a way that individuals in a film can make their own case, but it is also a mode that can act to undermine the interviewees, making them look foolish or deluded. Their interpretation of events or personal account may be rendered to seem trustworthy or untrustworthy depending on the context of surrounding shots or the nature of the statements being made in their own right.
Reflective
This is a style that is usually associated with more experimental documentaries, ones in which the filmmakers are interested as much in the process of making a film, of how reality can be constructed, as the actual content. At the simplest level the film may make no attempt to hide aspects of its construction - showing us the camera people for example.

Notes from
http://www.filmeducation.org/secondary/documentary2004/