Seeing as some folk have mentioned Errol Morris' excellent
"Fog of War", I'd like to add a note or two about this most accomplished of documentary filmmakers and his work on the nature of documentary making itself. Let's deal with their nature first...
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Documentaries are supposed to be objective studies of a given subject matter. They are supposed to "depict the truth" about that subject. The big problem is -
there is always an author involved - and it's not only the filmmaker providing an authorial voice. Following on from this is a second problem. They are, of course,
depictions of something, not 'the something' itself.
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Now, there is a TV series by Morris called
"First Person". For anyone considering what makes a good documentary, it's well worth watching some of these.
Here is a fairly good essay about the series.
The presence of an author is precisely what Morris explores in
"First Person". Each programme in the series is a first person narrative, a telling of a person's life -
by that person - by way of interview.
The intention of the series is to eliminate the external author as much as possible by allowing that person to tell their story direct to camera. But, as is commented on in the article linked above, these people don't make the films themselves and there is always a need for the external filmmaker to insert dramatic devices to keep an audience "entertained"(*). These devices can be the use of music, insertion of other footage, dramatisation sequences and so on. The way Morris handles these "essential devices", and the comment arising from this, is what makes the series crucial viewing for those wishing to scrutinise what documentaries are in the first place.
What is also explored and commented on well in the series is the inescapable fact that people narrating their own lives are also authors. Subjectivity is always at play. As such, Morris rightly points out that documentaries are always flawed to some extent or another.
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(*) Leni Riefenstahl's documentaries, especially
"Triumph of the Will", are NOT good documentaries. The authorial voice is simply too overwhelming. They are, however, outstanding examples of pioneering
dramatic filmmaking. No doubt about that.
Notice that the techniques she pioneered, like tracking shots, crane shots, pit shots and so on, are all techniques that
fictional and
dramatic filmmakers have gone on to exploit. The documentary world largely recognises that these are more obstructions and distractions from "the truth", and that they are used to entertain and awe the audience more than anything else. This, amongst other things, is what opens up Riefenstahl to the charge that she was a propaganda filmmaker, rather than a documentary filmmaker.