A two-part film. The first part is an exemplary, scrupulously researched documentary about the making and unmaking of Orson Welles’s 1942 Latin American documentary feature It’s All True — a project doomed by a change of studio heads at RKO, but also by its radical politics: Welles’s problack stance and his focus on the poorest sectors of Brazilian life upset RKO and the Brazilian dictatorship alike. (His career never fully recovered from the ensuing studio propaganda, and this film represents the first major effort after half a century of obfuscation to set the record straight.) The second part is a simple editing together of the rushes of “Four Men on a Raft,” the most ambitious (though least well-known) of the film’s projected three sections, and the only one whose footage has survived nearly in its entirety. It’s the true story of four courageous Fortaleza fishermen who sailed more than 1,600 miles to Rio to protest their economic exploitation by the men who owned their fishing rafts, beautifully shot in black and white by George Fanto. Welles had intended to narrate the section himself, but the writers and directors of this documentary — the late Richard Wilson, who worked on the original film, and critics Bill Krohn and Myron Meisel — have wisely opted not to second-guess Welles, simply presenting the material as it stands and adding music and sound effects. We also get to see some of the tantalizing surviving fragments of the other two sections, “My Friend Bonito,” which was shot in Mexico, and “The Story of Samba (Carnaval),” which includes some dazzling Technicolor footage. (JR)