Apart from the groundbreaking Sherman’s March (1986), this is the best entry yet in Ross McElwee’s ongoing autobiographical saga: it’s funny, profound, and beautifully organized, and for once the southern documentary filmmaker seems fully in control of all the inherent ironies. McElwee learns from his second cousin, a movie buff, that the Gary Cooper vehicle Bright Leaf (1950) may be a fictionalized portrait of their great-grandfather, who developed the Bull Durham tobacco brand in North Carolina in the late 19th century but was driven out of business by cigarette pioneer James Buchanan Duke. In the ensuing research McElwee visits sites important to the history of tobacco and interviews many smoking victims, but he also consults Patricia Neal, who costarred in Bright Leaf, and film theorist Vlada Petric. The resulting film explores McElwee’s lineage in all its complexities, noting the subtle relation between smoking and filmgoing as well as people’s tendency to validate themselves through movies (including this one). 105 min. McElwee will introduce the 7:20 and 9:40 screenings on Friday and take questions after the 7:20 show. Music Box. Reviewed this week in Section 1.