For more than 60 years, the Boston and Cambridge area has produced the world’s best, most innovative, and most influential documentary filmmakers. Robert Drew, Richard Leacock, D.A. Pennebaker and Chris Hegedus, Albert and David Maysles, Robert Gardner, Frederick Wiseman, Errol Morris, Robb Moss, and Ross McElwee are just a few of the greats with local roots.

The filmmakers of Harvard’s Sensory Ethnography Lab, or SEL, join this distinguished group. They have pushed the boundaries of nonfiction film with their uncompromising immersions into nature, and humanity. They film their subjects with a visual and auditory intensity but without context or editorial intrusions such as voice-over narration, explanatory texts, and any seeming preconceived notions. As such they cast viewers into the midst of an experience with little guidance but with a subtle shaping and Olympian gaze from which profound truths can emerge. They have aspired to an ideal — which sounds sadly ingenuous these days — expressed by the critic James Agee in 1948: “The camera can do what nothing else in the world can do: record unaltered reality.’’

The SEL reality can be seen in these three outstanding documentaries now available on the Criterion Channel.

Perhaps the most lyrical and accessible of these films is Lucien Castaing-Taylor and Ilisa Barbash’s “Sweetgrass’’ (2009), in which the filmmakers join the annual roundup and herding of sheep in Montana’s Beartooth Mountains. The sheep are shorn and taken to summer grazing in the public lands in the valley.

None of this is known until the film’s epilogue. Instead it opens with a close-up of a sheep’s face, its expression enigmatic like an ovine Mona Lisa. Later hundreds of sheep descend a mountainside like the conquistadors at the beginning of Werner Herzog’s “Aguirre, Wrath of God’’ (1972). Much of the film seems shot from the sheep’s point of view; the technique does not anthropomorphize the animals but enhances their mystery and otherness.

They also regard the human subjects with similar detachment as the herders shear the sheep, round them up, and shepherd them through the spectacular landscape. Their relationship to the animals varies from affectionate to resentful. In one scene, some devise an ingenious method of nursing an adorable newborn lamb, and in the next they sort them out by tossing them around like gunny sacks. One of the herders, a weathered and philosophical old-timer who in the John Ford version of the film would be played by Walter Brennan, calls the sheep “girls.’’ Another, a frustrated greenhorn at his wit’s end, calls them names that are unprintable.

Later he finally finds a signal for his cellphone and tearily tells his mother that he’ll never do this work again. As it turns out, he doesn’t have a choice. The epilogue notes that this was the last time this roundup would take place. “Sweetgrass’’ is not only a record of a living experience — it’s an artifact of a dying lifestyle.

The human element is more marginalized in “Leviathan’’ (2012), Castaing-Taylor and Verena Paravel’s intense (you might want to take some Dramamine before watching) study of a New Bedford-based fish trawler in the North Atlantic. The perspective instead is biblical, as the film opens with a quote from the Book of Job. “Upon earth there is not his like,’’ it reads in part, referring to the dreaded deep-sea creature of the title, “who is made without fear.’’

What is the Leviathan? Certainly not the fish netted and spewed gasping onto the ship to be beheaded, gutted, and packed away. Perhaps it is the trawler itself, a microcosm of a system in which everything in the world is there to be exploited and consumed.

Or maybe not. “Leviathan’’ overwhelms any single interpretation. It is a Rorschach crossed with an M.C. Escher print and a theme-park ride. Shot with numerous GoPro digital cameras set up in unlikely places and edited together with a claustrophobic verve, “Leviathan’’ doesn’t make it easy for the viewer to figure out what is going on. The camera submerges in the water where fish and meaty bits float by like objects in outer space and then pans upward to a ravenous flock of seagulls that look like they are visiting from Alfred Hitchcock’s “The Birds’’ (1963). The workers, who are glimpsed eating, watching TV, or engaging in conversations drowned out by the gurgles and clangs of the magnificent, cacophonous soundtrack, seem just a part of the same monstrous process, servants and victims of the dehumanizing beast.

The beast has a human face in Castaing-Taylor and Paravel’s remorseless and disturbing “Caniba’’ (2017). The subject is Issei Sagawa, who in 1981 while a student at the Sorbonne killed and ate a young woman. He was caught disposing of the remains, but because of legal technicalities was freed of charges and sent back to Japan. There he became a celebrity of sorts, publishing a manga version of his gruesome crime, making porn films, and even serving for a time as a food critic.

True to their style, Castaing-Taylor and Paravel do not share any of this background information in the film. Instead they plunge into extreme close-ups of the sickly, barely verbal Sagawa in conversation with his brother Jun. Issei demonstrates little remorse but much self-loathing. His rationalizations for his deeds are halting and half-hearted. His brother, meanwhile, laughs inappropriately and reveals his own sexual predilections, which, as he demonstrates, are the masochistic counterpart to his brother’s sadism. If there were a subgenre of weird brother documentaries, this should be included along with Joe Berlinger and Bruce Sinofsky’s “Brother’s Keeper’’ (1992) and Terry Zwigoff’s “Crumb’’ (1995). (The latter is featured in this week’s Doc Talk.)

There is no escaping these two in “Caniba.’’ The extreme close-ups of faces, eyes, torsos, lax mouths are relieved only by black-and-white home movies of the brothers as children and a snippet of Issei engaging in unconventional sex in one of his porn movies. They are trapped in some indeterminate interior space until the end when Issei is wheeled outside by a woman dressed as a chambermaid. “I can’t believe this,’’ he gasps as crows caw outside the frame. “I’m happy. It’s a miracle.’’

Go to www.criterionchannel.com/three-documentaries-from-the-sensory-ethnography-lab.

petervkeough@gmail.com.