Historians often regard documentary photographs as a critical form of documentary evidence that hold up a mirror to past events. Public and scholarly faith in the realism of the photographic image is grounded in a belief that a photograph is a mechanical reproduction of reality.
Susan Sontag captured the essence of that faith in her series of essays entitled On Photography when she wrote “Photographed images do not seem to be statements about the world so much as pieces of it.”
Yet the subjectivity of the photographer is not factored in when we look at a documentary image. Unlike a film or a written history we are unwilling to read documentary photographs as particular interpretations of a scene or event.
It appears to be more important to hang onto the assumption of of photographic realism as pure or unmediated. Yet we don't treat photographic images of consumer products in advertisments this way. We remain comfortable with the old myth that documentary photographs don't lie --or tell the truth--even though we know that the pictures are constructed, are shaped by aesthetic conventions and that photographic meaning is culturally enframed. The myth is what is important.