Finally showing his documentary film, “Famous Nathan,” at the Tribeca Film Festival was a personal triumph for cinematographer Lloyd Handwerker– it marked the completion of a project that was basically a lifetime in the making. After years spent interviewing relatives and friends, Handwerker, the grandson of Nathan Handwerker, the tireless Polish immigrant behind Nathan’s Famous hot dogs, churned out a tribute to his family that is, above all else, real. Handwerker’s documentary shows Nathan’s victories (“He was a god in Brooklyn,” one former employee states), and the sacrifices he made to get there, but he also uncovers a side of his grandfather that he never knew– a tough-as-nails boss who was both loved and feared by his staff. Handwerker even digs into his family’s deepest-rooted tensions, and uncovers, in part, how the business tore two of Nathan’s sons apart. “Famous Nathan” shows the tremendous highs and lows that came along with founding a New York City institution, and takes the audience along for a whirlwind trip down memory lane. Here are 10 things we learned.