It seems safe to assume Mistaken for Strangers is a leap forward from director Tom Berninger’s previous cinematic efforts. “This one’s about a barbarian with an identity crisis,” he says early on while holding up an old VHS, “who also goes through a murderous rampage.” A few years ago, when Tom got a job as a roadie for his brother Matt’s indie rock band, he figured the experience could yield a good documentary. Certainly it helped that his brother’s band is The National, which has become at least successful enough to play before thousands and to enjoy a private photo op with President Obama. And maybe it helped even more that Tom wasn’t granted access to the photo op: That’s just sort of how it goes when you’re the doughier, scruffier, less accomplished kin to The National’s frontman, which is what Mistaken for Strangers really is about. It’s a self-portrait from the inside of a big brother’s big shadow. Let’s just say Tom didn’t quite excel in the roadie job, which was thankless anyway, but he did get a movie out of it. And if Mistaken for Strangers lacks a murderous rampage, it does bring pretense-puncturing hilarity to the expansive sub-genre of rock documentaries, in which even the goofs have gotten too self-serious. Here, shambling sincerity seems like real refreshment, and it’s definitely a compliment to say that when Tom admits he took footage of himself crying, and Matt, in response, can’t keep from laughing, we want to do both.