"My work has always been about serial obsessions." says portrait photographer Timothy Greenfield-Sanders. When he was in his "artist" period, he photographed more than 700 luminaries of the art world over a 20-year span. Then it was musicians - he photographed them by the hundreds. Later he turned his lens on more than 100 fashion designers, and then he fixated on stars of pornography. His latest image obsession is prominent African-Americans.