At 89, Claudia Andujar still has her work cut out. For five decades she has photographed the Yanomami indigenous people, an Amer-Indian tribe who number 33,000 and live in 192,000 square kilometres of rainforest that straddle the borders of Brazil and Venezuela. Until the early 20th century they had lived almost entirely in isolation from the outside world, but since then disease, deforestation and climate change have taken their toll.

The election of Jair Bolsonaro in Brazil has proved a further threat. Vehemently against legislation protecting indigenous lands, last week the far-right president commented: “Indians are undoubtedly changing … They are increasingly becoming human beings just like us.”

“I now put all my efforts into the activism, into addressing Brazil’s political situation,” Andujar says as she prepares a retrospective at the Fondation Cartier in Paris, which shows a selection from a personal collection that runs to several thousand photographs. “I no longer take photographs, but use my archive to show how I saw the Yanomami. This present government has no respect for them. They have no understanding of who they are as people.”

The changing nature of Andujar’s work is chronicled in the show. Though the earliest images are straight documentary, the artist notes she was always more interested in striking up a human bond with her subjects than in approaching the work with professional detachment.

New vision … a house on the Catrimani River, Roraima, shot on infrared film in 1976. Photograph: Claudia Andujar

“I decided very early that I would not photograph if I felt I did not have a connection with the person whose picture I was taking,” she says. “Developing an intimacy with the individual and community came first. The photography was always secondary to that.”

Immersing herself in the culture of the Yanomami, it soon became clear that she would never represent their worldview through conventional composition. Instead, employing techniques, including double exposure, long exposures, the use of coloured filters or smearing of vaseline on the lens, Andujar started to produce a body of work a lot stranger and more faithful, she says, to the experience of the Yanomami people.

A room of the Paris show is dedicated to the shamanic rituals that are a key aspect to Yanomami cosmology. During these ceremonies the tribe believe spirits – xapiri – descend on the forest leaving trails of brilliant white light in their wake. Andujar represented this by shaking her camera as she took each photograph of the convulsing, gyrating shamans. One image shows a woman with her face obscured by curling trails of smoky white light dancing across the picture’s surface.

In another, a man, naked but for streaks of body paint, lies on the ground near a burning ball of light emitting from an unknown source. A funeral ceremony, in which the deceased is encased in a woven casket hung from a tree, is photographed through an otherworldly orange filter. A group of Yanomami are shown in layered multiples, using a double exposure, a way of reflecting the rhythm, movement and intense noise of the indigenous ceremonies.

Total immersion … a young swimmer in the Brazilian state of Roraima, photographed in the early 70s. Photograph: Claudia Andujar

Davi Kopenawa, a Yanomami activist and shaman, first met Andujar in 1977. “It was quite unusual for a white woman to come, a woman who wasn’t a missionary especially. Claudia took her time to get to know us; she slept in our shabono,” he says, referring to the ring-shaped wooden buildings that the Yanomami live in communally. “When the white people invaded our land, they took us by surprise and we weren’t prepared to deal with that first contact. Non-indigenous people wanted us to vanish, they wanted us to die ... It is still a dangerous battlefield out there for us, but to survive we need to confront it. These pictures are part of that. She was able to show them, show us, to the people of the city.”

Born in Switzerland in 1931, Andujar was raised in Oradea, a border town that has switched between Romania and Hungary. Her parents separated when she was nine. In 1944, as the German army closed in on the town, her mother took her to Switzerland, leaving her father, Siegfried, behind. He, and his entire extended Jewish family, perished in Auschwitz and Dachau.

This, Andujar says, lies behind the affinity she felt with the Yanomami. “I want to help the Yanomami to survive like my family did not. I think my work is dependent on the suffering of my childhood. My friends from school all died in Auschwitz. Everyone. Nobody, nobody survived.”

Kopenawa agrees Andujar’s childhood holds the key to her relationship with the Yanomami. “When the people of the world waged war against each other, Claudia suffered a lot. But that gave her the experience that is required to take images of the Yanomami.”

Vulnerable … a double exposure showing a child with an identifying number. Photograph: Claudia Andujar

After the war, Andujar moved first to New York, before settling in São Paulo in 1955. “I was conscious that I was looking for something that was missing from my life,” she says. “I never forced the relationship with the Yanomami, but there was something within me that was searching for a connection or purpose that they provided.” The longest of her repeated trips living with the tribe was over a year. Did she feel at home with them? “Yes, yes I did.”

The exhibition in Paris makes clear that Andujar’s journey from outsider to champion of the Yanomami was a long one. On one wall, showing her early work, is a fashion shoot from 1970 for Sententa magazine, in which a white model poses against the exoticised backdrop of an indigenous village. Elsewhere, the Yanomami are shown sympathetically, romanticised perhaps, with no hint to what some conservative anthropologists claim to be a violent culture inherent to the tribe. In 1968, the American anthropologist Napoleon Chagnon reported the tribe lived in a “a state of chronic warfare”. While disputes undoubtedly occur, Kopenawa rejects the generalisation, a claim backed by numerous studies since.

Andujar says that while she feels close to the Yanomami, and never felt scared, there is a power dynamic between her and them. “There are various beliefs in Yanomami about photography, and the capturing of what we call the soul,” Andujar says. “They have this fear, this suspicion of the camera. I only took pictures of Yanomami who got to know me first, when they knew why I was there. After a while they trusted me and would take no notice of the camera.”

In 1976, Adujar was back in São Paulo, struggling to get permission to return to the Amazon, when she heard of an ensuing measles epidemic among the Amerindian people. “I heard whole villages had disappeared, so many I knew died.” Kopenawa says that the disease was part of the ongoing persecution of his people by Brazil’s military dictatorship. “The white men were bringing all these diseases as the Transamazonian road was being built. I saw my mother and father die.” The tragedy precipitated a major change to Andujar’s career.

Claudia Andujar in London in 1989. Photograph: Robert M Davis/Oxfam/Courtesy Instituto Moreira Salles

Bruce Albert, a French anthropologist working in the area at the time, recalls that there was a strong desire by the dictatorship to keep news of the situation spreading. “The government agencies were spreading a lot of xenophobic, malicious rumours about us. They were furious we were there and one guy went round telling the Yanomami people we Europeans had come to steal their riches.”

Albert recalls Andujar arriving on the scene in a black VW Beetle. “I was asleep in my hammock when I heard this engine noise. Back in Paris I drove a white Beetle and this was the exact same sound. I thought I must be hallucinating, but I got up, went outside and there was Claudia silhouetted against the headlights of the car on the dirt track, composed as if it were one of her photographs. She was someone I had heard about from the Indians but not met. Here she arrived like a character in her own work.”

“I was undoubtedly aware that I was causing the government problems,” Andujar says, “They were watching me.”

All I can hope is when people look at my pictures they experience a connection with these people Claudia Andujar

Albert and Andujar, alongside Carlo Zacquini, a liberal Catholic missionary, went on to form Comissão Pró-Yanomami (CCPY), an activist group that campaigned on behalf of the Yanomami, and who were instrumental in pushing for a continuous tract of officially demarcated land for the tribe. Granted in 1992, this now stretches over 96,650 square kilometres. However, despite legal protections, Kopenawa estimates 20,000 illegal gold miners are operating in the Yanomami Park with the tactic permission of Brazil’s government.

It was through the CCPY, working with a group of doctors from São Paulo, that Andujar began coordinating a medical programme and the camera became but a tool in this activism. Yet the change of direction gave rise to what have proved to be her most haunting photographs.

Traditionally, Yanomami do not give each other names, referring only to their relationships with one another. In order to keep medical records, the team needed a way of identifying each patient. Each of the Yanomami were assigned a number, written on a wood necklace, which Andujar photographed them wearing. In their pragmatic simplicity, and numbering in their hundreds, the images show the Yanomami at their most vulnerable, facing the onslaught of sickness brought in by outsiders. And, while this process was born out of administrative need, it has become Andujar’s most biographical project, the young and old staring back at the camera, their numbers recalling those branded on the victims of the Holocaust.

Despite the power inherent in her photography, Andujar says she does not think art has a political agency. Gesturing to her life’s work, the artist shrugs. “This won’t change the attitude of Bolsonaro. All I can hope is when people look at my pictures they experience a connection with these people as people, people who, under this president, are suffering again.”

• Claudia Andujar: The Yanomami Struggle is at the Fondation Cartier, Paris, 30 January – 10 May. Now closed to coronavirus, the exhibition can be seen here