NEW YORK — Niels Diffrient — an industrial designer who combined elegance and efficiency in everyday objects, including telephones, cameras, airplane interiors, and, late in his life, office chairs that adjusted themselves to whoever sat in them — died June 8 at his home in Ridgefield, Conn. He was 84.
The cause was cancer, said his wife, tapestry artist Helena Hernmarck.
Mr. Diffrient, who spent his early years on a farm in Mississippi during the Depression, stood out for his natural drawing ability.
“He had two books: the Sears Roebuck catalog and the Bible,” Hernmarck said of his early childhood. “The Bible didn’t interest him, but the Sears Roebuck catalog — that immediately interested him.”
Mr. Diffrient spent hours drawing his own versions of items from the catalog. Two decades later, after Mr. Diffrient had attended art school, he applied his interest in consumer products as an assistant to the architect and designer Eero Saarinen, who hired him to help design chairs for Knoll.
After traveling to Italy on a Fulbright fellowship in the 1950s — he helped design an award-winning sewing machine while he was there — he quickly established himself in the expanding new field of ergonomics.
Mr. Diffrient called it “human factors engineering.” The goal was to blend function and form in a world that was increasingly dependent on mass-produced machines.
His immersion in the field began in earnest in 1955, when he started a quarter-century career with the design firm of Henry Dreyfuss. Dreyfuss had been influenced by the military’s interest during World War II in improving how a range of objects — not just uniforms. but also the cockpits of tanks and fighter jets — met human needs.
Mr. Diffrient helped design the streamlined and illuminated Princess phone, seats for John Deere tractors, and the Polaroid SX-70 camera, which, in addition to producing pictures instantly, could be collapsed into a jacket pocket. He also helped design the interiors of American Airlines jets, including the seats.
“The difference between us as designers and engineers is that engineers are fundamentally without an aesthetic motive,” he said in 2010 as part of a panel at the Cooper-Hewitt National Design Museum. “They work out something that functions mechanically or electrically and it’s functional, but they don’t add that extra something that’s poetic, cultural, visually satisfying.”
Beginning in the 1970s, Mr. Diffrient collaborated on a series of manuals that provided data-driven guidelines for designing furniture and spaces for all people, including children, older adults, and those with disabilities.
The first volume, “Humanscale 1/2/3,” was published in 1974.
He left the Dreyfuss firm in 1981 and, his wife said, struggled for more than a decade to find a new niche. In the late 1990s, when he was past 70, he found it in the office chair. His creation, which he called the Freedom Chair, became a competitor of Herman Miller’s popular Aeron chair.
“The problem with many ergonomically designed office chairs is they have all these knobs and levers — to adjust the seat height, recline of the backrest, height of the armrests, the headrest, and so on,” he told The New York Times Magazine in 2003. “But most people never use them. The things that this chair does to address that problem are: When you recline, you don’t have to adjust the chair — it adapts to your body weight. When you decide that the armrests are not where you want them to be, you grab one or both arms and move them up or down. They’re coordinated, so if you pull one up, the other follows.”
The Freedom Chair, whose lowest-end model sells for about $700, has won numerous design awards and helped make Mr. Diffrient something of a brand name late in his life.
“He always said he was happy to end on a high note,” his wife said.
Mr. Diffrient was born in 1928, in Star, Miss. His family later moved to Detroit, where he graduated from Cass Technical High School and received a bachelor’s degree from Wayne State University. He attended Cranbrook Academy of Art in Bloomfield Hills, Mich., as a graduate student.
In addition to his wife, whom he married in 1976, he leaves three children from a previous marriage, Scott Diffrient, Julie Miller, and Emily Diffrient; a brother, Roy; and a sister, Betty Herring.
Asked the source of inspiration for his distinctive skill in blending the technical and the aesthetic, Mr. Diffrient told The Times he ultimately had one goal.
“Why would you design something,” he asked, “if it didn’t improve the human condition?”