footage from government sources, and so on and so forth all may be subjects for a documentary film.
Documentary film makers are typically the writers, directors, and producers. Often they may act as cameramen as well.
Documentary films are most often made for TV but in more recent times there have been more of them made as direct-to-video, made-for-video, straight-to-video, or straight-to-DVD formats in which they were never first played on TV or in the theaters but were simply distributed for home-viewing.
Some major motion pictures when released in DVD format also come with bonus DVDs that act as documentary films of the making of the movie.
Documentaries also often feature re-enactments of events that could not or were not originally documented on film such as historical events from the year 1776.
There have also been “mockumentaries”