Ironically, given that it is a movie expressly and entirely about the communicative power of the moving image, Cameraperson gives us the answer key to understanding everything about it in the form of a title card that precedes any other footage: "For the past 25 years I've worked as a documentary cinematographer. I originally shot the following footage for other films, but here I ask you to see it as my memoir."

The "I" in that sentence is Kirsten Johnson, best known for shooting 2014's Citizenfour, though if there is any shred of justice in this world, she will going forward be best known for this very movie instead. At the risk of sounding hyperbolic, Cameraperson is the most important work of art of 2016.

Now then, let's walk back from that (because obviously, it's not that, and even if it were, we'd need at least a few more years to be sure), but not too very far. Whatever else it is, Cameraperson is an extraordinarily exciting and stimulating challenge to documentary form, like nothing else seen this year, or last year, or maybe ever (the last film I saw that was even in the same wheelhouse was The Beaches of Agnès, from 2008). It is, as Johnson tells us, a memoir; it is also an act of metacriticism of the boldest sort. Johnson's work throughout her career has touched on multiple genres of documentary, but generally speaking all of her best-known work - in films like Citizenfour, The Invisible War, Pray the Devil Back to Hell, her projects with Michael Moore - has been in the realm of what we might call political awareness documentaries, journalistic films attempting to cast light on something horrible and important in the world, either with an eye towards ginning up activism, or simply to bring out the truth where it's been missing. Certainly, that's where she gets most of her footage in Cameraperson; more than any other single source, she's primarily drawing on I Came to Testify, an episode of the 2011 PBS documentary series <Women, War & Peace, about the women of the Bosnia town of Foča, sharing their stories of being raped en masse by Serbian soldiers. And there's a lot to be said about that footage, which forms one of the two sustained through-lines in the movie, but for right now, let's stick with the fact that, generally, what Johnson does is journalism, and what we generally think of journalism is that it strives for objectivity. At the very least, that the persons (camera persons, even) who do journalism have found a way to remove themselves from it.

What Cameraperson does is to point out how much tendentious bullshit that all is. In its best moments (no, that's not a fair way to phrase it; the whole thing is best moments), the film rips the veil of objectivity off to remind us that Kirsten Johnson is a human being who had feelings and thoughts in her head while she was filming. In the first clip we see after that title card, a flock of sheep mill around, and in come's Johnson's voice, anthropomorphising and interpreting the animals' feelings of dismayed confusion at the camera crew. In the second clip, a road stretches off at a diagonal line, with stormclouds gathering, as the occasional car drives past: it is a strong graphic composition, beautifully colored, and a perfectly painterly backdrop for the film's opening credits. And then come the moment that made me realise that Cameraperson was going to be one of my favorite films of the year: a bolt of lightning strikes on the left side of the frame, and Johnson audibly gasps in joy. A few seconds later - maybe it was longer, I wasn't keeping track of time by this point - she sneezes and jostles the camera.

And that, that is everything. We know two things about Kirsten Johnson: the prickly, ionised air that precedes a storm makes her sneeze, and she's delighted by beautiful lightning strikes. The movie doesn't always draw her in quite so directly a fashion, though it does so frequently enough: hearing her complain about too much haze, confer with the director about where to position a shot, quibble with the U.S. government about how much of the Guantanamo Bay prison she's allowed to show in any one shot. What matters is not that the whole movie is made up of unusable outtakes of a cinematographer chattering and moving her camera; what matters is that enough of it is that we always remember thereafter that all of this footage is being filtered through one person who has opinions about what she's doing, and who lets those opinions inform what she assembles.

And that, then, becomes part of the great triumph of Cameraperson, which is a new incarnation of one of those selfsame advocacy docs, depicting the bureaucratic claustrophobia of Gitmo in one passage and stonily giving us a tour of how the entire physical place of Foča was repurposed as a prison camp and veritable factory for rape. Here, though, the focus is entirely on subjectivity, not objectivity, asking us not merely to be upset and outraged by the various crimes we see, but to think about how we come to know about those crimes: how they are chosen and shaped by directors, by editors - even by cinematographers! - and to confront the core reality that no documentary nor any act of journalism is genuinely free from individual perspective.

Doubling down on that reality, much of Cameraperson isn't even slightly engaged in this political messaging. Much of the footage comes from what appear to be Johnson's home movies, of her children, her father, and her mother, suffering from Alzheimer's disease. These are presented by the director and her editor, Nels Bangerter, with no distinction from any other footage; there's not a frame of the movie identified by anything other than location where it was shot, which sets everything, be it a sobering interview with a rape survivor, a furious boxer moments after losing a match, or a grandfather helping his grandchildren bury a dead bird they found in the backyard, in a single continuum. It's the only shortcoming of any real note within Cameraperson that this continuum is sometimes pieced together without any clear logic behind it, and while the juxtapositions of disparate moments sometimes reveal startling affinities, sometimes, they just seem to communicate "this is the footage I thought looked pretty". Which is often enough - the footage does look pretty, and even the footage that doesn't tends to become pretty by virtue of context: Cameraperson is a movie about what it means to look at people and the places in which they are found, and it demands that we think closely about what images do, how they are designed. At times, Johnson even designs them right before our eyes, cleaning windows or repositioning elements in the shot to get the most impact from a composition.

At any rate, the flow of images is powerfully evocative even when it's not clear what they're evoking, always suggesting how Johnson associates image with meaning, and implying her feelings about her footage without necessarily requiring that we feel the same way. The moments with her family, of a certainty, mean more to her than they could possibly mean to us, but it's nonetheless moving to understand what she feels towards her sick mother, especially when they show up on camera together (the only time in the film we see Johnson's face, 95 minutes into a 102-minute film), and understand that for her, this is as much a part of the world to be recorded and preserved as the stories of the women from Foča, or the revelations of Edward Snowden. This is, after all, an autobiography, however strange a form it takes: it is the story of what Kirsten Johnson knows and thinks, and how she engages with the world. At one point, she abashedly tells a gathering of the Foča women, five years after filming them the first time, that she'd enjoyed their company and personalities so much that she'd forgotten all about their tragic stories. That's Cameraperson writ small: a tribute to what happens in front of the camera, how it is captured, and the eternal present of cinema.