A “special interest” film is defined mostly by the narrowness of it audience. As opposed to a mainstream film, which will, its producers hope, appeal to a large portion of the potential viewing audience, a special interest film is expected to appeal to a much more focused segment of the audience-most likely those viewers who already have an interest in the film’s subject matter. A special interest film doesn’t try to win over the masses; it sticks to what it know, and it attempts only to please viewers within its niche.
Many special interest films are documentaries that focus on a very specific subject. They may address social or cultural topics that are outside the mainstream, or they may explore the lives and work of lesser-known historical or cultural figures. Instructional films fall into this category, too, since viewers are unlikely to watch them purely for their entertainment value.
Cult films, theatrical films that are enjoyed by a loyal but relatively small audience, can also sometimes be considered special interest films. They are loved enthusiastically by their fans, but they are unlikely to win over a broad audience and so are relegated to the fringes of genre designations.