A man and a woman walk toward the camera down a wet cobbled street at night, holding hands, both in dark coats. She is looking at him. He is looking ahead. Behind them the crowd, the tram and the coloured lights of some installation dissolve into a field of soft discs, and the pavement runs away under their feet as a broad grey wedge. It is a photograph, taken in the last few years, and it belongs to a picture type that is three hundred years old.