Documentarians in the Cambridge, Massachusetts, filmmaking community have been instrumental in developing the personal documentary into a major force in modern cinema. Ross McElwee, in his breakthrough Backyard, fashioned a new kind of documentary voice, a literary voice-wry, witty, subtle, often poignant. It's a voice he has explored in virtually all of his feature filmmaking, and that Alfred Guzzetti pays homage to in his recent Time Exposure. McElwee and Guzzetti's longtime colleague at Harvard University (and UC Berkeley graduate) Robb Moss chose a more self-effacing approach in Riverdogs, his rarely screened film about a rafting trip through the Grand Canyon.