It's 35 years since Wim Wenders began making documentaries in earnest. In that time, he has produced such exemplary profiles as Lightning Over Water (1980) about Nicholas Ray, Tokyo Ga (1985) about Yasujiro Ozu, Notebooks on Cities and Clothes (1987) about fashion designer Yohji Yamamoto, Buena Vista Social Club (1999) about a band of veteran Cuban musicians, and Pina (2011) about choreographer Pina Bausch. Now, he has teamed with Juliano Ribeiro Salgado to make The Salt of the Earth, a tribute to Brazilian photographer Sebastião Salgado that provides a magnificent showcase for the striking monochrome images that have been captured in trouble spots around the globe and have often come in for as much criticism as praise for aestheticising misery. Maybe because his co-director is the son of his subject, Wenders avoids asking too many awkward questions and, as a result, this often feels like a fawning paean rather than a critical assessment.

Sebastião Salgado was born in 1944 in Aimorés in the south-eastern state of Minas Gerais. Following an itinerant childhood, he studied economics at the University of São Paulo before going into exile in 1969 to escape life under a military dictatorship. While working for the International Coffee Organisation, he frequently visited Africa to compile reports for the World Bank. It was during an expedition to Niger that Sebastião started taking photographs. Encouraged by his wife, Lélia Wanick Salgado (who has bought him his first camera), he started taking news photographs in 1973. He worked for a few years for the Sygma and Gamma photo agencies, but spent 15 years with Magnum before quitting in 1994 to concentrate on documentary projects for his own Amazonas Images company.

While Lélia tried to place his pictures with editors and raised their sons, Juliano Ribeiro and Rodrigo (who has Down Syndrome), Sebastião travelled to danger zones in a bid to capture the dignity of humankind in extremis. Having launched his solo career with the photo-essay, The Other Americas, he joined forces with Médecins Sans Frontières to explore the nature of deprivation and extreme poverty in The Sahel, the End of the Road. However, he made his reputation with Workers, a record of working conditions in the Serra Pelada mine in the 1980s that included several images that have rightly been described as Brueghelian for their density and unflinching frankness.

Sebastião reveals to Wenders that many of those enduring the mud and heat were not exploited peasants, but graduates and urban professionals who had been drawn to the gold mines like so many prospectors before them in the hope of striking it rich. He compares the scenes of toil with such the construction of such biblical edifices as the Tower of Babel and the Pyramids or the excavation of King Solomon's Mines. But it is also easy to see why critics like Susan Sontag and Ingrid Sischy could accuse Sebastião of composing his shots with Western sensibilities in mind and he does let slip in some of his conversations with Wenders that he sometimes felt he was witnessing spectacle and theatre rather than calamity and atrocity.

Such was the ambition of later empathetic projects like Exodus and Migrations that Sebastião was often away for months on end, as he liked to live in the communities he was profiling before he started shooting. Showing how the refugee's tent had become the commonest form of dwelling, these investigations into the way famine, war and economic exploitation impacted upon places like Ethiopia, Kuwait and Rwanda began to take their psychological toll on Sebastião and he and Lélia embarked upon a project to reforest with two million trees the parched cattle ranch he has inherited in the Mata Atlantica. Such was the success of the Instituto Terra enterprise that its lessons have been applied worldwide and this reconnection with the land prompted Sebastião to visit places as different as Siberia and Papua New Guinea for his latest epic, Genesis.

Having seen little of his father while growing up, Juliano Ribeiro jumps at the opportunity to work alongside him on this tome and his colour images of Sebastião at work perfectly complement the black-and-white interview passages, for which Wenders used a semi-transparent mirror to reflect the pictures in discussion so that they share the frame with Sebastião's face. While such ingenuity is acute, Wenders might have asked about funding sources and the reasons why he left Magnum in the mid-1990s, He might also have afforded Lélia more time, as she is clearly more than the little woman indoors, while much more should have been made about the ethics of photo-reportage and photographic art, as so many memorable images appear to have been carved into the celluloid and it is impossible to divorce the often shocking scenes from their compositional precision.

There has been a glut of photodocs of late, with the better examples including Richard Preiss's Bill Cunningham in New York (2010), David and Jacqui Morris's McCullin (2012), Sebastian Junger's Which Way is the Front Line from Here? The Life and Time of Tim Hetherington, John Maloof and Charlie Siskel's Finding Vivian Maier (both 2013) and Michael Whyte and Luke Dodd's Looking for Light: Jane Bown (2014). In each case, the eponymous shutterbug has been lionised and Wenders leaves one in little doubt that he has been in awe of Sebastião Salgado ever since he had been moved by the Serra Pelada pictures. But he seems curiously incurious about Sebastião's influences, his sources of inspiration and his working methods. Evidently, the subject set some untraversable perameters. But surely Wenders could have used his voiceover to express the odd trenchant opinion instead of spouting fulsome praise that sounds like it has been lifted in its full purple verbatim from a book jacket or publisher's catalogue.

Considering he is the co-director, Juliano Ribeiro slips into the shadows a touch too conveniently in the latter stages, while Lélia is woefully neglected. Sebastião makes a frustratingly guarded interviewee until he presents his pessimistic verdict on the future of the vicious human animal and warms to the theme of eco-preservation. With a little more blunt forthrightness about the horrors he had witnessed and a markedly less cine-manicuring, this might have been more than a handsomely sincere puff piece.

Kim Longinotto takes things in a romantic direction in Love Is All: 100 Years of Love & Courtship, a compilation essay that interlinks material from the BFI and Yorkshire Film archives. This is becoming a popular format with British film-makers and Longinotto clearly takes her cues from Penny Woolcock's From the Sea to the Land Beyond (2012) and Martin Wallace's The Big Melt (2013). But, while she makes some inspired selections and, courtesy of editor Ollie Huddleston, achieves some charming and witty juxtapositions, Longinotto struggles to weave a cogent thematic thread between the clips. Consequently, while this provides some shrewd insights into changing British social and cultural attitudes in the 120 years since the birth of cinema, it says surprisingly little about love and the national character.

As the material is presented in a largely chronological order, the action opens with a Freudian flourish, as a train disappears into the darkness in GA Smith's The Kiss in the Tunnel (1899). But such flashes of humour prove to be fleeting, as Longinotto shifts her focus on to the emancipation of women, race relations and gay rights. Garnered from a range of documentaries, shorts, home movies and features, the images follow the path of true love from the first date to matrimony and domestic bliss. But Longinotto dots proceedings with intriguing digressions, featuring the likes of a women's football team, a speed skating race, excursions to the country and the seaside, dance hall scenes, inner-city kids skipping after an ice-cream cart, neighbours socialising on the street, and lots and lots of trains. However, as in the last reel of Giuseppe Tornatore's Cinema Paradiso (1988), the emphasis is on embraces, whether they are chaste or furtive, pecked or passionate, French or very stiff upper lippedly British.

The majority of the footage derives from British Transport shorts and such actualities as Claude Friese-Greene's The Open Road (1924), Mary Field's The Mystery of Marriage (1932), the Central Office of Information's David: Story of a Welshman (1951), Tony Richardson and Karel Reisz's Momma Don't Allow (1956), Claude Goretta and Alain Tanner's Nice Work (1957), Michael Grigsby's Tomorrow's Saturday (1962) and John Irvin's Gala Day (1963). The latter quartet are all Free Cinema offerings and it's instructive to see the changing ways in which everyday life was recorded as the decades passed. But Longinotto less successfully tries to incorporate mini-narratives distilled from such acclaimed features as Maurice Elvey's Hindle Wakes (1927), EA Dupont's Piccadilly (1929), Horace Ové's Pressure (1975), Stephen Frears's My Beautiful Laundrette (1985), Isaac Julien's Young Soul Rebels (1991) and Sarah Gavron's Brick Lane (2007).

These extracts illustrate the passing of Victorian morality as the 20th century moved towards free love in the 1960s and the gradual acceptance of mixed race and same sex unions. Much more compelling, however, are the snippets from the Colonial Film Unit's Springtime in an English Village (1944), which shows a young black girl being crowned Queen of the May in the Northamptonshire village of Stanion; Lloyd Reckford 's Dream A40 (1964), which charts Michael Billington's unease at discovering his attraction to Nicholas Wright; and W. Hugh Baddeley's Michael Goodliffe-narrated infomercial, Don't Be Like Brenda (1973), which follows its heroine from idyllic dates with her first beau to giving up her unwanted baby for adoption. There is also something grimly amusing about the fact that the closing shots of a waving crowd have been lifted from Joseph Best's docudrama, Whatsoever a Man Soweth (1917), without revealing that this was made to warn Canadian soldiers about the dangers of contracting a venereal disease in wartime London.

Accompanying the pictures are songs culled from the back catalogue of Sheffield musician Richard Hawley. Occasionally, sound and vision match, but the lyrics sometimes seem to be at odds with the footage and the resulting effect is a little dislocatory. It might have been useful to have the clips identified on screen as they appear (although this, of course, would annoy those viewing this as a film poem rather than an exercise in cine-sociology). Yet, for all such minor flaws, this remains an accessible and enjoyable snapshot of an ever-evolving populace. Longinotto is primarily an advocatory film-maker and this assemblage works best when it has a subtext. But, even though the spoken word is largely absent, it's still possible to detect the voice that informed Divorce Iranian Style (1998), Sisters in Law (2005) and Pink Saris (2010).

There is much less to admire in Anna Odell's The Reunion. Known in her native Sweden as a provocative conceptual artist, Odell made headlines while studying at Stockholm's prestigious Konstfack Art Academy when she was charged with fraudulent practice, raising a false alarm and resisting arrest after it was discovered that she had feigned a suicide bid on a city bridge in order to gain admittance to a psychological unit for her film, Unknown Woman 2009-349701. Perhaps the notoriety of this stunt explains why this follow-up feature won the FIPRESCI prize for best debut at the Venice Film Festival, as the cinematic merits of this self-satisfied exercise in self-pitying look-at-meism are exceedingly modest.

As the guests mingle at a dinner to mark the 20th anniversary reunion, Anna Odell arrives late. She makes awkward small talk, but it is clear she is ill at ease in such chic company. When the toasts are made, therefore, it comes as something of a surprise when she gets to her feet. She introduces herself and wonders how many of these enjoying an evening of nostalgia remember the torment that they inflicted on her at school. Retaining her composure as the first protests arise from the floor, Odell recalls a series of humiliations that she endured at the hands of her so-called friends. She is persuaded to sit down. But, when the host hopes that their children enjoy the same camaraderie they all shared, Odell jumps back to her feet to accuse some by name of bullying her and she continues to hurl accusations at the top of her voice as she is forcibly removed from the room.

This concludes `The Speech' part of the proceedings and `The Meetings' opens with Odell revealing that this is actually a short film that she has written and directed because not only did she not attend the class reunion, but she was also not invited. However, while the classmates in the vignette are played by actors, Odell wonders how her real peers might react to seeing themselves being subjected to some harsh home truths and she contacts them with a view to attending a screening.

It's at this point that an already shaky conceit starts to judder. Odell tries to shoot her encounters with those who accept her offer with raw spontaneity. But her images are too consciously composed, the reactions of her `classmates' are too studied (almost as if they were actors like their counterparts in the first segment) and the eavesdropped snippets are too loaded with meaningful admissions and tokens of regret or recrimination. Blurring the lines between fact and fiction has always made documentary film-making so fascinating and frustrating. But it would appear that these are re-enactments rather than records of real events. Moreover, if these people are genuine alumna, they appear either to have exceeded Odell's wildest expectations by pure chance or to have consented (or been coerced) (in)to colluding with the director to achieve her desired reaction. Wherever this truth lies, the merest suspicion that the footage has been scripted, rehearsed or shaped undermines its integrity and, thus, robs it of its value as a work of catharsis, social critique or art.

Odell is aware that the culprits for making her life a misery came from the upper echelons and she is determined not to let her chief persecutor off the hook. Therefore, she tracks them down and confronts them in situations and places designed to cause them maximum discomfort. Among those she ambushes is her biggest nemesis and Odell ends her film walking the corridors of her school as if she has reclaimed them for herself and she can now move on with her life because her past traumas have been healed.

Scandinavian film-makers clearly have a thing about capturing social gatherings at their moment of implosion. In this regard, Odell follows in the wake of Thomas Vinterberg's Festen (1998) and Ruben Östlund's Involuntary (2008). But there are dozens of examples of misfiring reunions, including Michael Miller's National Lampoon's Class Reunion (1982), Francis Ford Coppola's Peggy Sue Got Married (1986), George Armitage's Grosse Pointe Blank (1997), David Mirkin's Romy and Michele's High School Reunion (1997) and Jon Hurwitz and Hayden Schlossberg's American Reunion (2012). On the small screen, Tina Fey in 30 Rock and Kaley Cuoco in The Big Bang Theory even got to face up to the fact that they had been doing the bullying.

But, while Odell can be forgiven for failing to break much new ground in her discussion of class, cliques and childhood cruelty, she should not be let off so lightly for making this paean to what Sight and Sound's Nick Pinkerton aptly called the `sanctity of victimhood' so pretentious, ponderous and predictable. Artists invariably use vanity projects to self-project, but this takes humblebragging in an entirely freakish direction. If it was supposed to be a denunciation of the way Swedes deal with their nonconformists and outsiders, then it fails dismally. However, as a means of getting Odell noticed further and wider than ever before, it has already worked its oracle.