To capture Cambridge Rindge and Latin students in her photo “Senior Prom, 1982,’’ Olive Pierce was on the dance floor herself, so close that a viewer can almost hear the couple kiss at the left side of the picture. On the right side, another couple embraces in a slow dance, a white hat pressing tightly against the boy’s bangs. A frilly shirt cuff peeks from his tuxedo sleeve, and his right hand, clad in a pinky ring, slips below the base of his date’s back, a few inches south of propriety.

“Olive savored more than anything the human moment,’’ said documentary filmmaker Alex Gibney, a longtime friend. “Her compositions are rich, but that’s not the thing that sets her apart. It’s the humanity she captures.’’

Her photos of the Rindge and Latin students, shot while she taught photography there from the late 1970s to the early ’80s, are collected in her book “No Easy Roses: A Look at the Lives of City Teenagers.’’ She brought a similar searing intimacy to photographing Cambridge’s Jefferson Park housing project in the 1970s and Iraqi children in the 1990s, and to spending a decade living on and off among Maine lobster fishermen while gathering material for “Up River: The Story of a Maine Fishing Community,’’ a book-length collection of black and white photographs published in 1996.

“Taking pictures of people at close range is a delicate business, and it takes a while to feel out the boundaries,’’ she wrote in that book, adding that “it requires constant vigilance to see people as they really are.’’

Ms. Pierce, who moved from Cambridge to live full time in Rockland, Maine, about 15 years ago, died May 23 in her home, where at 90 she still lived alone with occasional assistance from friends who helped prepare meals when necessary as she became more hobbled by arthritis. “She was a very kind person and a giving person,’’ said her son, Laurence of Cambridge, “and she had a very devoted following.’’

“These photographs speak with honesty and quiet authority,’’ Globe reviewer Kelly Wise said of Ms. Pierce’s 1992 exhibition at the Bunting Institute in Cambridge of photos that would become part of “Up River.’’ The photos at that show included “Burial, 1988,’’ in which men carry a polished casket through a leaf-strewn field, and “Nissen bread, 1991’’ of a little girl pulling a Radio Flyer wagon filled with bread loaves. Her face is hidden behind a smiling Raggedy Ann mask. A small RV trailer sits at the far side of the yard.

Reviewing Ms. Pierce’s 2009 show in Cundy’s Harbor, Maine, Philip Isaacson took note in the Maine Sunday Telegram of the relationship between the photographer and her subjects that was as much a part of the exhibit as the photos. “She is an outsider and they have delivered themselves in trust to her: She has both honored that trust and met them head-on,’’ he wrote. “That balance tugs at my heart.’’

“She was a documentary photographer, but one with not an ounce of exploitation in her,’’ Ms. Pierce’s son said. “She was very, very true to her subjects. She would never publish anything or reproduce anything without the permission of her subjects.’’

Gibney, whose work includes last year’s “Going Clear: Scientology and the Prison of Belief,’’ is a lifelong friend of Ms. Pierce’s son’s. “She was a great person and a great photographer for the same reasons,’’ Gibney said. “She had an unbelievable capacity to talk with just about anybody. She was always curious, she would ask great questions, and she was utterly guileless. She was always straight with people, and I think that’s what disarmed them.’’

The second of three siblings, Olive Robbins was born in Chicago in 1925 and grew up in the affluent suburb of Lake Forest. She wrote that she was “cared for by nannies’’ in a family headed by her mother, the former Sarah Farwell, and her father, Laurence Robbins, who had served as an assistant secretary of the US Treasury Department during the Eisenhower administration. “My father was a successful banker but not as rich as the friends whose lifestyle he tried to keep up with,’’ she wrote in a preface to “Up River.’’

She was “sent away to boarding school as was the custom in Lake Forest’’ — in her case, to Chatham Hall, an Episcopal girls’ school in Virginia. “Tenement farmers living in shacks on backcountry roads were new to me,’’ she recalled. “I wanted to see more.’’

At Vassar College, she majored in English and graduated in 1945. After working at the Art Institute of Chicago she moved to Boston. Through the Unitarian Service Committee, she traveled to Poland in 1948 as a secretary to a medical team, bringing along a camera her father had bought her and photographing the post-war ruins of Warsaw and the Auschwitz concentration camp.

Returning home, she taught fourth grade at The Meadowbrook School in Weston until marrying George Pierce in 1951. “Her photography career really started with taking photographs of me and my sisters,’’ Laurence said, and that soon extended to other children and families.

Ms. Pierce studied photography with Berenice Abbott, whose students had included Diane Arbus, and later with Paul Caponigro. A grant from the Radcliffe Institute “turned me toward documentary work,’’ she wrote, and she began photographing subjects in Cambridge. She taught at the New England School of Photography from the late 1960s to the mid-1970s, and when her marriage ended in 1976, she cofounded and taught in the Cambridge Rindge and Latin photography program.

She also was twice a Bunting fellow at Radcliffe, and in 1999, while in her mid-70s, Ms. Pierce traveled illegally to Iraq to photograph the impact of economic sanctions on the country’s children.

While she was still married, Ms. Pierce and Harriet Harvey, who is Gibney’s mother, had purchased a 100-acre wilderness tract that covered nearly all of Maine’s Marsh Island in Muscongus Bay. There the family built a vacation camp that was very primitive and very beautiful, her son recalled. One day while heading back to town in a boat, Ms. Pierce called out to a passing lobsterman. That chance encounter led to her longtime friendship with two fishing families, the Harveys and the Carters, who became the subjects of “Up River.’’

“I liked the ruggedness of the land, the richness of the life, the intermingling of people of all ages,’’ she wrote. “The clutter was appealing to a photographer’s eye as was the presence everywhere of boats.’’

She was just as drawn to how the light played on the landscape and the water. “The tonality was mine — the strong contrasts, the bright highlights, the depth of the blacks,’’ she wrote.

In addition to her son, Laurence, Ms. Pierce leaves two daughters, Anne of Cambridge and Elizabeth of Arlington; a sister, Sarah Bradshaw of Brookline; and six grandchildren.

Family and friends will gather to celebrate her life on June 18 on Marsh Island in Maine; a service in Cambridge will be announced.

The many exhibitions of her photos included the 2003 retrospective “Olive Pierce: Forty Years of Photographs’’ at Duke University and a show of her fishing community photos at Bowdoin College that ran through mid-January this year.

“I have been held to this work by the effort to achieve a balance between my subject and my craft,’’ she wrote in “Up River.’’

Maine’s terrain, she added, “is mined with cliches — the weathered house, the stack of lobster traps, the boat riding at anchor in the fog. To break through to a deeper layer of observation and to translate what is seen into a photograph that stands on its own as a picture has been my challenge.’’

Bryan Marquard can be reached at bryan.marquard@globe.com.