Photography is inescapably a memorial art. It selects, out of the flow of time, a moment to be preserved, with the moments before and after falling away like sheer cliffs. … [Photography] is about retention: not only the ability to make an image directly out of the interaction between light and the tangible world but also the possibility of saving that image. A shadow thrown onto a wall is not photography. But if the wall is photosensitive and the shadow remains after the body has moved on, that is photography. Human creativity, since the beginning of art, has found ways to double the visible world. What photography did was to give the world a way to double its own appearance: the photograph results directly from what is, from the light that travels from a body through an aperture onto a surface.
But when the photograph outlives the body — when people die, scenes change, trees grow or are chopped down — it becomes a memorial. And when the thing photographed is a work of art or architecture that has been destroyed, this effect is amplified even further. A painting, sculpture, or temple, as a record of both human skill and emotion, is already a site of memory; when its only remaining trace is a photograph, that photograph becomes a memorial to a memory. Such a photograph is shadowed by its vanished ancestor.