Historians often regard photographs as a critical form of documentary evidence that hold up a mirror to past events. The public and scholars believe the photographic image is a mechanical reproduction of reality. "Photographed images do not seem to be statements about the world so much as pieces of it." (Sontag, pg. 23) Many famous documentary photographs have resulted in a photographer capturing a compelling scene, whether by arranging subject matter or experimenting with alternate composition.
Since photographs are regarded as truthful, photographs are frequently used to illustrate history textbooks. Publishers usually select images to accompany history texts, and the images are used merely as illustrations and not as historical documents in their own right, although many of the photographs in textbooks can stand independently as historical documents.