Almost all of us take photographs every day using our smartphone. The vast majority of them are never printed, but are shared online or stored in digital form. As a result, we generally do not experience these photographs as physical objects, but as intangible images. Photos that are printed are, however, not necessarily regarded as objects either. One of the reasons for this is that the visual idiom of photography is largely realistic: a photograph of a person is an exact likeness of that person. Photography is a ‘transparent’ medium – when we look at a photograph it is as if we are looking directly at what is portrayed in the photograph. The material of the photograph itself becomes invisible, as it were. The properties of the material of which a photograph is made are however vital to the story told by the photograph.