There is in fact no such thing as an instantaneous photograph. All photographs are time exposures of shorter or longer duration, and each describes a discrete parcel of time. This time is always the present. Uniquely in the history of pictures, a photograph describes only that period of time in which it was made. Photography alludes to the past and the future only in so far as they exist in the present, the past through its surviving relics, the future through prophecy visible in the present.
— John Szarkowski, The Photographer’s Eye.