Sebastião Salgado has traveled the world taking photographs of human suffering. For 40 years, he's taken brutal and beautiful black and white pictures of starvation in the African Sahel, workers in the burning oil fields of Kuwait, and the hellish conditions of gold miners in Brazil. Now, the documentor has become the documented. A new documentary, "Salt of the Earth," features Salgado describing some of his most moving photographs. We speak to one of the film's directors, kicking off a week of interviews with the filmmakers behind this year's Oscar-nominated documentaries.