If it's nourishing objectivity you're after, look away now. Tracing the same ten-year period of Ali's life - from champ-in-waiting to post-draft debacle comeback trail - as Michael Mann's movie, Klein's camera certainly manages to capture some genuine hidden gems.
That said, the footage can frustrate with its rawness and, at nearly two hours, this sometimes feels like one mighty long history lesson. More significantly, though, the majority of the personal and political intricacies of Ali's many personas are merely glossed over, resulting in what occasionally feels like little more than a PR exercise.