Charles Baudelaire characterized le flâneur as a "gentleman stroller of city streets," he saw le flâneur as one who portrayed from the outside and participated in the life of the city. While remaining a detached observer, le flâneur played a role in the cityscape. His stance was simultaneously part of and apart from the relationship between the individual and the greater populace.
(A modern) application of le flâneur (is) to street photography (and) comes from Susan Sontag in her 1977 essay, On Photography. She describes how, since the development of hand-held cameras in the early 20th century, the camera has become the tool of le flâneur:
"The photographer is an armed version of the solitary walker reconnoitering, stalking, cruising the urban inferno, the voyeuristic stroller who discovers the city as a landscape of voluptuous extremes. Adept of the joys of watching, connoisseur of empathy, the flâneur finds the world 'picturesque.'"
After the Wikipedia entry.