The cavernous lobby of New York City's Metropolitan Museum of Art is jammed with people, but it is impossible to miss Alex Katz. The artist famous for his bright figurative paintings is standing by the information desk wearing a parka so blindingly orange it looks radioactive. Orange is one of Katz's favorite colors, and the jacket, adorned with reflective silver strips, is the kind that a guy on a road crew might wear to direct traffic in a rainstorm. But this French-made parka is downright chic, rather like its owner, who looks at least a decade younger than his 82 years, with a smooth head (he shaves it daily) and features as sharp as those of the suave figures who populate his paintings.

He has come to the Met to see an exhibition of works by Pierre Bonnard, the French Post-Impressionist who was a big influence when Katz was starting out. "Bonnard was very important in the early 1950s," Katz says. "His painting was in the same direction as [Jackson] Pollock—away from a contained plane. It was all over light, just light and color." He goes on: "They're great paintings; they have great atmosphere. Bonnard's great with reds and oranges—it is very hard to get transparency with red!"

A maverick from the beginning, Katz came of age when Abstract Expressionism still reigned, yet he turned to painting landscapes and the human figure. Over time, his paintings got bigger. "Appropriating the monumental scale, stark composition and dramatic light of the Abstract Expressionists, he would beat the heroic generation at their own game," the critic Carter Ratcliff wrote in a 2005 monograph on Katz.

"It was an open door," Katz says today. "No one was doing representational painting on a large scale."

Taking cues from Cinemascope movies and billboards, his highly stylized pictures also anticipated Pop Art. His deadpan evocation of flat, bright figures had an everyday quality that linked them to commercial art and popular culture. Early on, his work was often panned. Clement Greenberg, the critic famous for championing the Abstract Expressionists, "actually went out of his way to say how lousy I was," Katz recalled in an article he wrote for the New Criterion.

But critical opinion has never seemed to matter to Katz. "Alex is a man of supreme confidence and clarity," says Adam Weinberg, director of the Whitney Museum of American Art. "He quickly realized what he was about and was absolutely undaunted and single-minded in that pursuit. That persistence enabled him to weather the contradictory movements in the art world."

Today, Katz's popularity is exploding. His quin­tessentially American evocations of people at cocktail parties or the beach and his landscapes of Maine took off in Europe, especially after the collector Charles Saatchi showed off his Katzes in his private museum in London a decade ago. The painter has also found a substantial new audience at home in the United States. As figurative painting made a comeback in the late '80s and '90s, a younger generation of artists began to see Katz with new appreciation. "Artists were looking at their predecessors, but there were not a lot of them who'd continued in that figurative zone consistently, with his level of detachment," says Weinberg. "Coolness is something that artists of all generations admire—cool in the sense of detachment, but [also] cool in the sense of hip."

Like Warhol before him, Katz has no problem bridging the worlds of art and fashion, whether creating artwork for W magazine or getting supermodels such as Christy Turlington and Kate Moss to sit for him. "I've always been interested in fashion because it's ephemeral," he says. Katz himself even modeled for the J. Crew spring catalog this year.

The stylish octogenarian is, by his own account, as busy as ever. So far this year, Katz has had exhibitions in Milan and Catanzaro in Italy, Paris, Vero Beach in Florida, Finland and at his New York City gallery, PaceWildenstein, where he recently showed a series of monumental sunsets.

"I want to compete with the kids!" he said one afternoon while sitting on a leather sofa in his sparsely furnished SoHo loft, in Manhattan, where he has lived since 1968. Just beyond the living room is his studio, an airy, white-walled space that floods with daylight. There isn't a speckle of paint on the linoleum floor. "I don't like mess," says Katz. "I don't like paint on my clothes or my hands or my furniture."

A series of gigantic, freshly painted canvases are propped up around the studio—each a frieze of enormous heads, some of men, others women. The pieces are reminiscent of what the artist was doing decades ago, most memorably in a series of Times Square murals he made in 1977. "I've been working to make this kind of ‘artificial realistic' painting," he says of the latest efforts. "I want to do something larger than a descriptive painting."

To make one of his large works, Katz paints a small oil sketch of a subject on a masonite board; the sitting might take an hour and a half. He then makes a small, detailed drawing in pencil or charcoal, with the subject returning, perhaps, for the artist to make corrections. Katz next blows up the drawing into a "cartoon," sometimes using an overhead projector, and transfers it to an enormous canvas via "pouncing"—a technique used by Renaissance artists, involving powdered pigment pushed through tiny perforations pricked into the cartoon to recreate the composition on the surface to be painted. Katz pre-mixes all his colors and gets his brushes ready. Then he dives in and paints the canvas—12 feet wide by 7 feet high or even larger—in an epic session of six or seven hours. "It's all done wet on wet," he explains. The paints blend and become luminous.

From far away or in reproduction, Katz's pictures look hyper-smooth, but up close you notice the brushstrokes and the small bits of accent color that attract the eye. More than painterly technique or the image depicted, though, his work is about the style. "I'd just as soon have the style be the content, style rather than form," he says. "The style is what puts all the disparate parts together."

Katz's wife, Ada, walks into his studio, offering coffee. A visitor might be forgiven for presuming to have met her before, so familiar is she as Katz's muse and model over the course of their 51-year marriage. The long hair that brushes her shoulders is gray now, but the expressive dark eyes in her serene face are the same as those that look out from under a hat in Red Coat (1982), from under an umbrella in The Blue Umbrella (1972) and from all six Adas wearing the same glamorous cocktail sheath in one of his most popular works, The Black Dress (1960). Her husband says she's an American version of Picasso's famous model and mistress Dora Maar. But, Katz is quick to add, "When I saw photos of Dora Maar, I said, ‘Picasso cheated on her neck and shoulders!' Ada has a much better neck and shoulders."

Katz's speech still bears traces of his childhood in Queens, New York. The son of an émigré who'd lost a factory he owned in Russia to the Soviet revolution, Katz "drifted into fine art," he says. He was studying commercial art at a local vocational high school when he began to draw from casts of antique sculpture and won admission to the Cooper Union School of Art in Manhattan. He met Ada, who had studied biology at New York University, at a gallery opening in 1957. "She's a great beauty," he says. "The gestures are perfect. She's like an actress in a sense. She's also a very sharp Italian girl from the Bronx—you can't beat that." (The couple have one son, Vincent Katz, 49, a poet and art critic.) Social life with Ada in the '50s and '60s revolved around poets—Frank O'Hara, John Ashbery, Kenneth Koch—as much as painters. "They were dealing with everyday experiences, in a kind of sophisticated way," Katz recalls. (In Katz's 1967 portrait, Koch looks slightly uneasy behind a big pair of horn-rimmed glasses.)

Katz may be best known for his portraits, but he has also devoted himself to landscapes—works that are daring precisely because they lack people and "throw away the lifelines" of human interest, noted the critic David Cohen. "They work on Katz's own painterly terms or not at all." Many are evocations of Maine, where he has gone to paint every summer for the past 60 years, and where he has a house and studio on a small lake.

"It's a conceit in a way," Katz says. "It's like you can paint the same river twice differently. I often paint in the same place. It's like painting Ada over and over again—to see if you can get something else out of the same subject matter."

The Colby College Museum of Art, in Waterville, Maine, has devoted a 10,000-square-foot wing to Katz's artworks, the majority of which he donated. In addition, he has purchased numerous pieces for the museum by artists such as Jennifer Bartlett, Chuck Close, Francesco Clemente, Elizabeth Murray and, most recently, Marsden Hartley (a Maine native). Five years ago, he curated a show at Colby of such young art stars as Elizabeth Peyton, Peter Doig and Merlin James, who work in the same figurative territory staked out by Katz.

Katz's agelessness is hard won. He's a super-jock, who runs and does "tons of" push-ups and sit-ups when he's home in New York; in Maine, he works out, he says, up to four hours a day—running, bicycling and swimming. How far can he run? "As far as I like. I can outperform a lot of 21-year-olds physically," he says.

He says he also competes with artists half his age "for the audience," though with limited weaponry. "My subject matter is not particularly interesting," he says with a smile. "It's not hot subject matter—you know, no crucifixions, no violence, no sex." His tools are color and light, and his own stripped-down vision of the world. "I try to make painting that looks simple," he says, and cites seeing a Velázquez portrait of a Hapsburg infanta in a traveling exhibition at the Metropolitan Museum when he was in his mid-20s: "It was nothing—so simple! Something could be so simple and so much. Just a green background, a little girl—everything was perfect. There's no story line. It's immediate. He painted directly. He saw it, he painted it."

A Katz painting, for all its coolness, projects feeling. "The pictures are supposed to be lyric, they're supposed to give you an up," he says. "I want to make something that's sort of like your happier condition. Impressionist pictures are basically that—Impressionist painting is a happy lie."

Katz's happy lies are those timeless beautiful faces with perfect skin, or the trees of a Maine summer, forever leafy and green.

Yet, sometimes, even the elegant Ada can look grave, on the brink of tears. And the landscapes can be dark—most notably, his haunting "nocturnes" or night scenes, with their nuanced layers of darkness far moodier than so many of the crisp and colorful portraits. In the recent series of sunsets, for example, Katz, in essence, is capturing the passing of time. It was hard to make the oil sketches, he reports—only 15 minutes or so on a Maine porch before dusk fell. In these large paintings, seen together, time passes quickly, and the sky becomes an impossible orange, reflected in the lake. Then, in the next painting, the lake has turned dead, to gray. These pictures, with black trees in the foreground, are elegiac—their subject is the last few minutes of daylight that no one can hang onto.

Luckily, there is consolation, even what Katz calls a kind of eternity, in art itself. "That's the difference between a painting and a sunset," he says. "The painting will stay with you, but the sunset disappears." And so Katz keeps his focus on the moment, painting like there's no tomorrow.

Writer Cathleen McGuigan lives in New York City.
Photographer Stephanie Sinclair is also based in New York.