Inspired by an intense love of photography, the following pages make no attempt to build a theory, perhaps assuming such a project to be impossible in its own nomadism; they try instead to pin down one of photography's strangest powers, often called the "reality effect": source of a unique pleasure before the world's beauty, of an inexhaustible questioning of the nature of reality, of historical events and social violence, of art's shifting definition, memory or the self, a marker of technology's effects on our perception and, above all, of time's plasticity, an effect that is also the motive for photography's constant self-questioning.