Some of the people who are now manipulating photos, such as Andreas Gursky, make the argument - rightly - that the 'straight' photographs of the 1940s and 50s were no such thing. Ansell Adams would slap a red filter on his lens, then spend three days burning and dodging in the dark room, making his prints. That's a manipulation. Even the photographs of Henri Cartier-Bresson, with all due respect to him, are notoriously burned and dodged.