The Nan movie: "All the Beauty and the Bloodshed"

Via such projects as 2010's The Oath, 2014's Citizenfour (on Edward Snowden) and 2016's Risk (on Julian Assange), the documentarist Laura Poitras established herself as a keen observer of world affairs, if not always a reliable judge of character. Her latest, the newly Oscar-nominated All the Beauty and the Bloodshed, appears to mark a sidestep into the realm of the blue-chip artworld profile, although its subject has proven barely less engaged with the state of things. Nan Goldin is the American photographer who's found renewed artistic purpose by taking up arms against the Sacklers, the family who've pumped millions into the world's galleries and museums - money largely gained from pumping opioids manufactured by their pharma manufacturing arm Purdue into millions of Americans. Goldin was among those who got hooked - she knows whereof she protests - but then Poitras's film frames its subject as someone who's long borne close personal witness: to the unhappy household in which she grew up, to the suicide of a depressive older sister, to spells in foster homes, to acute teenage shyness, to the community of boho outsiders she fell in with in 1970s New York, and how that community was all but abandoned to the ravages of AIDS by the prevailing powers-that-be. Poitras flexes her reportage muscles filming those sit-ins by which Goldin and her activist associates have confronted Sackler-backed institutions over the past decade, and there are fleeting, sometimes spectral clips of the work of those fringe and experimental figures Goldin travelled with along the way (John Waters, Bette Gordon, Amos Poe, Vivienne Dick). Yet the bulk of the film's two hours is made up of photographs kept very much like receipts.

These potent prints and Polaroids are an obvious focal point for any Goldin film, and - in this one - an obvious boon. This is another example of a doc where the filmmaker has had a lot of the investigation and documentation done for them; where the big creative choices concerned how to lay this story out. Poitras seizes upon Goldin's work as elegantly framed evidence - of a life, a career, and a natural empathy with those at the margins. There's an inbuilt artistic progression to be observed, from freewheeling early assignments (portraits of scenesters, glossy-candid depictions of the sex act and its aftermath) to what's positioned as the artist's mature work, highlighting the detritus and damage addiction leaves behind. For much of the first hour, the montage is simple and effective: plentiful rostrum camera (or digital equivalent) in the Ken Burns/Morse tradition, opening with some neatly engineered contrast between Goldin's images (subtext: this is life how it's actually lived, warts and all) and the glibly aspirational tone of those print ads the Sacklers placed in medical journals and checkout-counter magazines to hawk Oxycontin to the aching masses. Here is the cause; here, as documented by Team Goldin, are the deleterious, often deathly effects. This gallery stretch of the film is accompanied by a running commentary from Goldin (still with us, and approaching her 70th) in her raddled-scratchy, Patti Smith-like voice. We're forever aware we're getting Nan in her own words, as has become documentary convention in recent years - and as we discern what she wants to talk about, what she doesn't, and where she wants to steer our eyes and ears, All the Beauty and the Bloodshed starts to reveal its limitations as a piece of journalism.

You will come away from Poitras's film with no doubt as to Goldin's status as a notable artist, the hardships she's overcome, and her commitment to the marginalised. (The five-star reviews the film has engendered represent an understandable form of hero worship - for here is a woman who has battled personal demons, taken on some part of the Establishment, and triumphed on both fronts.) Yet for a long while it seems oddly content to skate over the surface of Goldin's images. The commentary keeps cueing potential lines of investigation - that sibling's suicide, Goldin's sex work, her drug dependency and eventual recovery - only to suddenly move on to the next image, the next phase of this life. Part of the trouble is that this is either two films in one (a retrospective and a campaign doc) or two-and-a-half films in one (retrospective, campaign doc, and an overview of the same opioid crisis Alex Gibney took many more hours to parse in HBO's The Crime of the Century). The title invokes the all-encompassing, yes, but I felt Poitras piling an awful lot onto the one plate - you keep wanting to stop so as to better unpack each segment's implications, or redirect the questioning altogether. The first half, surely, would benefit from a little more director-subject interplay, something to break up the metronomic flow of Goldin's words and images; in the second, Poitras and her hardy editors do begin to knit in some of the material their subject has been withholding, while building a belated momentum within the campaigning narrative. Was Goldin's personality - the force of will that sent the Sacklers packing from the National Portrait Gallery and elsewhere - too strong for the filmmakers to resist? Make no mistake, there is plentiful art in these two hours. (Art enough to win the Golden Lion in Venice, art enough for an Oscar nod in a so-so year for the documentary form.) My question would be how much of that is Goldin's art, and how much we can comfortably ascribe to Poitras. Provocative as it remains in places, there are stretches where ATBATB resembles merely the most illustrious of Goldin slideshows, placidly yielding the floor to its far spikier subject.

All the Beauty and the Bloodshed opens in selected cinemas from tomorrow.