That’s only partially due to the Icelandic post-rockers’ otherworldly approach to music. Shot during a two-night stand in 2008 at London’s historic Alexandra Palace, French-Canadian director Vincent Morisset transferred digital footage to 16mm film, then again, through prisms and “found objects,” according to the “Inní­­” website. Combined with the abstract and always beautiful cinematography, the result is a stark 75 minutes that captures the soul of one of the planet’s most alien bands.

“Ný batterí,” the dark centerpiece of “Agaetis Byrjun” (arguably its best album) opens this film, casting a monochromatic shadow on the rest of it. And in case the beginning didn’t feel creepy enough, lead singer Jón Þór Birgisson twists and writhes as he saws at his guitar with a violin bow, but with all the stage’s darkness, he might be strangling a man, for all the audience can tell.

There’s no “Gobbledigook” here. The nine songs selected span the band’s five discs, but are most often melancholy at their very brightest (the exception being the childish, “Inní mér syngur vitleysingur” where Birgisson shares the piano bench with Kjartan Sveinsson in one of the film’s most affecting moments). For the most part, Birgisson’s groaning guitar hangs over funereal drum marches and murky bass play from Georg Hólm, although his boyish voice cuts through the swaths of gloomy sound, whether he’s singing into his microphone or the strings of his instrument.

“Inni” is interspersed by snippets of unexplained shots of the group winning the Iceland Music Award, riding bicycles, and being asked awkward questions by NPR; the choice provides only a bare-bones backdrop (I’d recommend watching “Heima” if you want more in the way of a conventional documentary), but none’s really needed here. Morisset’s intimate cinematography focuses on the tiniest storytelling details: the fringe on Birgisson’s tailored jacket, the way Sveinsson’s head bounces and just how hard Orri Dýrason’s cymbals flap when they play “Festival,” (which you can watch below) for instance. You’re so close to the band that you forget about the actual Alexandra Palace audience, at least until the end when they make the oddest of appearances.

You’ll walk away scratching your head in awe.