In August 1949, Life Magazine ran a banner headline that begged the question: Jackson Pollock: Is he the greatest living painter in the United States? Ed Harris’ feature film “Pollock” (2000, 118 min) is a look back into the life of an extraordinary man, a man who has fittingly been called an artist dedicated to concealment, a celebrity who nobody knew. As he struggled with self-doubt, engaging in a lonely tug-of-war between needing to express himself and wanting to shut the world out, Pollock began a downward spiral.