The purpose of documentary photography is primarily to record details of an unfolding event or situation in an honest and factual manner. In many respects the definition of documentary work overlaps that of photojournalism. The principal difference is that photojournalism label is normally used to describe news and rapidly changing events, whereas the documentary label is intended for longer term stories - such as the progressive destruction of the rain forests.

Documentary photographs are often created and used as historical documents or records rather than a source of art. When a subject is well documented the record may be used to encourage social, environmental or political change. Although documentary images are by definition factual, a documentary photography has great flexibility to tell a particular story in a manner of his or her choosing.

Documentary and artistic photography are generally considered to be quite different, indeed at opposite ends of the spectrum of work, but some photographers have skilfully combined the two types - at least in part. The resulting work can be intense, shocking and extremely powerful, and has the potential to rouse emotional reactions from viewers.