Anyone who was left cold by the 2003 "The Blues" miniseries (or, for that matter, anyone who really liked it) should seek out this documentary. This is the real stuff, not archival footage, that was happening right in front of the cameras. And while the modern blues we see on the festival circuit is a celebration of tradition, this is the thing itself.
Most of Deep Blues is shot in Northern Mississippi hill country, where Fred McDowell is the figurehead of local tradition (as opposed to the Mississippi delta, where Charlie Patton & Robert Johnson are the deities). Impovrished and isolated, the blues lives there in a form mostly untouched by the Chicago sound and it's bastard son, rock & roll. Because of this purity, Deep Blues is, at times, like a window back into the original blues era.
Robert Palmer has that sort of goofy music critic presence that some find annoying, but I can't think of any one else who could have done it any better.
This is perhaps the best blues documentary that I have ever seen. And, as an interesting side note, Deep Blues was instrumental in launching a record label (Fat Possum) that brought many of the stars of this movie to a much wider public; R L Burnside and Junior Kimbrough in particular were saved from obscurity by Deep Blues and Fat Possum Records. Do yourself a favor: if you like blues uncut, check this out, and look into Fat Possum's catalogue.