Errol Morris's passion for sleuthing dates back at least to his days as a private detective and runs through his work as a documentary filmmaker in movies like "The Thin Blue Line" and his most recent, "Tabloid." In his new book, "Believing is Seeing," he turns his magnifying glass on photography. He and I discussed (and occasionally debated) the veridical nature of photography, the impact of digital retouching and the truth value of his own films. Then, in the second half of the show, an excerpt from my 2009 interview with documentarist Jonathan Stack on his film Iron Ladies of Liberia. It's about the presidential administration of Liberia's Ellen Johnson Sirleaf, who shared in this year's Nobel Peace Prize.