In photography blur has the peculiarity of being at once the most basic error to avoid and an extremely difficult form to achieve, somewhere between primary technical mistake and artistic ambition. Pauline Martin takes the reader through the history of the medium seen through the prism of blur, from the invention of the process to the present day, showing that depending on the period it has been considered now a positive value, now a negative one. In a historical and thematic development the works presented are punctuated by quotations, so that a dialogue is created between the pictures and the way blur has been described by authors and artists as different as Charles Baudelaire, Julia Margaret Cameron and Pierre Bourdieu, bringing out what is at stake in our perception of the world.