THE relationship depicted in “Keep the Lights On” isn’t one that most people would want to revisit. The film, based on part of the director Ira Sachs’s life, immerses viewers in the love and protracted dysfunction involving Erik, a needy documentary filmmaker, and Paul, a charming yet drug-addicted lawyer in publishing.
“Keep the Lights On,” which opens Sept. 7, is a balancing act typical of this director of “Forty Shades of Blue” (2005): a film based on highly intimate and painful autobiographical material that doesn’t rely on audience members having that knowledge to exert a hold on them. In “Keep the Lights On” those who know the back story will recognize the movie, set in Manhattan, as a refraction of Mr. Sachs’s past relationship with Bill Clegg, the literary agent who wrote of his struggles in “Portrait of an Addict as a Young Man.” But knowing that back story is by no means crucial to appreciate the film.