He is ultimately like a painter with a palette of light, a draftsman with the geometry of everyday life. His images are infused with a naturalness that emerges from the illumination of the world — light reflecting what is real — reconstituted in luminous, grainy, black-and-white. For an artist renowned as one of the finest photographers of the human landscape, it seems especially revealing that today, at 91, Henri Cartier-Bresson likes to speak most about drawing and painting.

He now spends a great deal of time without his trusty Leica camera, drawing sketches of people and landscapes, still observing the world around him. But through five decades of extensive travel and significant friendships with artists, scientists and political figures — all in pursuit of his vision — Cartier-Bresson was not often without his Leica. With it, he helped reinvent photojournalism after World War II.

Although he was an artist by training and outlook, Cartier-Bresson was one of three founding members of Magnum Photos, a photographers' collaborative that became, and remains, one of the world's premier picture agencies. Even in the heyday of mass-market magazines, in the 1940s and '50s, he made pictures that had the gravity of art. He traveled the globe — to India to document its emergence from colonialism, to China to shoot a revolution, to Washington to photograph the powerful and the powerless and a city reflecting a beautiful light. And throughout his career he accumulated a stunning range of acquaintances, whom he photographed freely. A number of these pictures will be on exhibit at the National Portrait Gallery starting October 29.

He seems bashful, almost shy, about his extraordinary talent; looking back on his achievements, he refers to photography as a thing of the past. "My passion has never been for photography 'in itself,'" Cartier-Bresson wrote in 1994, "but for the possibility — through forgetting yourself — of recording in a fraction of a second the emotion of a subject, and the beauty of the form."

However self-effacing he has become, Cartier-Bresson's pictures have influenced generations of followers. His photographs have entered our collective memory, lodged there like signposts in the visual narrative of this century. His portraits, of famous and anonymous lives, bring personalities to life by merging their often-complex psychologies with an economy of formal elegance. He is equally at home as an artist and as a journalist.

Such categories, however, are immaterial to his work, which moves fluidly back and forth between both concerns. He remains an enigmatic personality whose art thrives on such contradictions. Best known for his ability to capture in his pictures the movements of people through the world, Cartier-Bresson skillfully zeros in on gestures and glances and movements through time, absorbing the touch of his subjects from environments charged with aesthetic tension. He lays bare the hidden details that symbolize the basic nature of our lives.

Henri Cartier-Bresson has long considered photography an intuitive venture, one that connects keen observation with feeling and an uncanny sense of how to construct a picture. "To take photographs," he once said, "... is putting one's head, one's eye and one's heart on the same axis." In other words, his working process combines sentiment and sensitivity for his subjects with an informed ability to look into the world around him. Still, to come to grips with his intentions, it is important to place his work in the context of his complicated and independent spirit, one that has thrived amid the turbulence of the 20th century. "He's a free man, which is very rare in this century, free of all opinions," says photographer Gilles Peress, a current member of Magnum.

The seeds of political turmoil that erupted in World War II were scattered across Europe and the United States in the 1920s and '30s. As Cartier-Bresson came of age in Paris, many European avant-garde artists were breaking both aesthetic and psychological taboos, subverting artistic and literary traditions. There was an atmosphere of both collaboration and debate in Parisian cultural circles. Cartier-Bresson's interest in the arts, exemplified by his rebellious idealism and connections to Surrealist writers and painters, was a form of defiance for a well-off youth.

Born on August 22, 1908, in Chanteloup, outside Paris, Cartier-Bresson was steeped in the arts at a very young age. Henri's mother was from Normandy, his father a bourgeois Parisian textile magnate, a frugal but very wealthy patrician. His uncle, whom he referred to as "my other father," was a painter. Cartier-Bresson began reading modern literature — Dostoyevsky, Rimbaud, Proust and Joyce — at a young age and began to study painting seriously as a teenager. In 1927, he began to study with Andre Lhote, a rather conservative Montparnasse painter best known as an educator, whose goal was to connect modern art with the great traditions of French painting.

Cartier-Bresson soon met Surrrealist artist Rene Crevel, who introduced him to the works of Andre Breton and Louis Aragon. "I was marked, not by Surrealist painting, but by the conceptions of Breton," said Cartier-Bresson, "[which] satisfied me a great deal: the role of spontaneous expression and of intuition and, above all, the attitude of revolt." At the same time he began to haunt the jazz clubs of Paris.

Cartier-Bresson's connection to the Surrealist imaginations of Aragon and Breton helped shape his awakening interest in photography. He began to take serious pictures in 1929, experimenting with a small camera and looking intently at isolated details found in shop windows or lying about on the street. He had also discovered the work of Martin Munkasci, a Hungarian photojournalist and fashion photographer whose graphic sense of movement and design, coupled with his use of small, portable cameras, animated his images of running, jumping and playing people.

As a means of transcending his family's bourgeois foundation, Cartier-Bresson sought to explore the world with this new technology and an embrace of Surrealist inventiveness that was foreshadowed in a few awkward paintings he made during a visit to Cambridge. In 1930, perhaps inspired in a broad way by the capricious, literary spirit of the French poet Arthur Rimbaud, he set out for Africa, where he spent a year hunting wild animals and photographing, only to return home after contracting a severe case of blackwater fever. When he finally processed his film from this journey he found it was mostly ruined by moisture that had seeped into his cheap camera.

Cartier-Bresson continued to roam during the early-to-mid-'30s, from Paris through Eastern Europe, Spain, Italy, Morocco, Mexico and the United States. Inspired by Surrealist notions of "automatic writing" and intuitive action, coupled with a growing interest in African cultures and art, he began to make photographs of everyday activities as if drawing in a sketchbook.

Like the great Parisian documentarians Eugene Atget and Brassai, Cartier-Bresson wandered the streets without a specific destination. He followed his impulses, seeking some new sense of reality in the tension between the privileged and underprivileged, the extraordinary and the ordinary. At this time he also began to use his trademark German-made Leica, a small, precision camera he learned to manipulate almost as an extension of his body. It gave him the freedom to move.

Cartier-Bresson's early photographs from the '30s are among his most inventive. They cement for him a process and vision that combine the intimacy and compositional acuity of photographs by André Kertész with the humanitarian structure and subtle political consciousness of Jean Renoir's films. Cartier-Bresson worked for the master filmmaker in the late '30s as assistant director on several documentary and narrative projects. He then entered the French military service as a photographer at the onset of World War II and was captured. On his third attempt, he escaped and returned to Paris to join the underground, an experience that tempered his experimental leanings. It was after the war, in 1947, that he founded Magnum with Robert Capa and David Seymour.

As his work began to focus on human drama and history, Cartier-Bresson's photographs of people began to dance with psychological insight. Even though he was making portraits from the beginning, he understood that this approach was something new and complex. He wasn't trying to make images that presented a likeness or dramatic description of a person. His portraits evoked an intimate, possibly unspoken, dialogue between the artist and the people he portrayed. The exhibit at the National Portrait Gallery, "Tête à Tête: Portraits by Henri Cartier-Bresson," offers a rare opportunity to eavesdrop on some of these conversations.

One of the earliest images in the exhibition depicts Joe the trumpeter and May, an anonymous couple Cartier-Bresson photographed during his first trip to the United States, in 1935. What is most striking about this picture is the tremendous poise and confidence it reveals. The relationship between the photographer and the subjects is clear and direct. May is looking straight at the camera, head cocked, and her eyes meet ours in a quiet, if protective, gaze. Behind and above her, Joe's body is turned at more of an angle, his head tilted away, but his eyes catch the light and lens just so, revealing something of a soulful vulnerability and thoughtfulness. It is a penetrating image, one in which an obvious tension is diffused by the relaxed and graceful touch of Joe's hand on May's shoulder. The torqued angle of his head and shoulders twists and pulls against the frontal pose of his partner to animate their complex personalities. It's the kind of fluid, syncopated tension — force and resolution — one finds in jazz. We don't really know who Joe and May are, but we don't need to — their special relationship is the subject of the portrait.

A photograph like this reveals how deeply Cartier-Bresson understands painting. His strategy here involves superimposing a kind of classical composition on Joe and May's improvised pose. In photographing a 1930s couple in New York City, he puts into play some of the same structural and compositional concepts found in painted portraits by Ingres or Cezanne from 19th-century France. Clearly, he learned the lessons of Lhote.

While working to untangle fragments of personalities in his portrait photographs, Cartier-Bresson is also telling us something about himself. The conversations in these pictures include the photographer and his internal vision — indeed, they reflect his thinking about image-making. "If, in making a portrait, you hope to grasp the interior silence of a willing victim, it's very difficult, but you must somehow position the camera between his shirt and his skin," he wrote in 1996. "Whereas with pencil drawing, it is up to the artist to have an interior silence."

But if Cartier-Bresson believes that it is impossible to really know a person, inside and outside, through a photographic portrait, what do his portraits really tell us about people? After all, we can know the texture of someone's skin from a photograph, but can we see and understand what's inside?

This is the question that he is posing in his work; the answer lies inside the photographer. Cartier-Bresson tells us that we cannot comprehend a subject's "interior silence" without this silence coming from the artist himself, from the connection of his mind, eye and hand. Yet this connection — of thought, vision and action — is inherently present in his photographs. By using the camera like a pencil or brush, a true extension of his interior thinking, he comes close in these pictures to perceiving what is behind the mask of the face — that "spark of life," as art historian E.H. Gombrich calls it in his introduction to the exhibition catalogue for "Tête à Tête."

One of Cartier-Bresson's best-known pictures portrays writer and philosopher Jean-Paul Sartre, bundled in an overcoat against the cold, standing on a bridge, lost in thought and looking out past and beyond the photographer. It is through this one photograph that most of the world knows Sartre. He is clearly in conversation with another man, visible on the right edge of the image. One feels the weight of their thoughts, but it is the sense of silence, the lack of any imagined sound, that shrouds this image in mystery. Its representation of this void, a visual translation of "silence," is right on the surface.

Made in 1946, this photograph is less about Sartre's personality than it is about his ideas. As a leading proponent of existential philosophy, he proposed that people are free and responsible for their actions, and that human suffering ultimately stems from this responsibility. Cartier-Bresson's portrait is indistinct, the image filtered by its thick, grainy surface; it is a picture of a man absorbed by his environment. Its narrow depth of field — only the main subject is in sharp focus — forces the eye to penetrate this veneer, to rest on the philosopher's face, to gaze into his eyes. He does not return the glance. However, the bridge itself invites us on, a vague diagonal line pointing the way across into a foggy background. It looks like we are walking into a Surrealist painting by Giorgio de Chirico or an image from a poem by Andre Breton, where unconscious connections to this vague photographic landscape are heightened by fragments of Sartre's categorical thought.

Cartier-Bresson used a similar strategy in his portrait of Simone de Beauvoir, made in 1947. She stands at an angle, pushing right on the surface of the picture, sharply focused against a background that dissolves into an almost abstract scene of three anonymous figures passing each other on the street. This juxtaposition of the upright author and light-filled, dreamlike background creates an animated tension between the two. They are like different worlds that co-exist, one that we see and another that is created in the mind of the photographer. The notion that the picture depicts the character of a real person, de Beauvoir, and conveys something of her personality, activates her conversation between these fictional worlds and the form-filled surface of the photographic print itself.

The portraits of Sartre and de Beauvoir pose interesting questions about the real-life truths and abstract fictions that emerge in these works by Cartier-Bresson. By questioning the illusionary nature of truth, he makes visible one concept that enlivens the work of the French existential writers in the 1940s — the idea that the things we see and experience in our everyday lives may hold within them unseen truths that we alone are responsible for deciphering.

"Sometimes and somehow, almost out of a superior craftsman's good manners, he seems able to leave his lens out of the picture," writes critic Lincoln Kirstein in his preface to the catalogue of Cartier-Bresson's 1947 exhibition at the Museum of Modern Art. "His portrait subjects are not shot; they get themselves taken at tactful intervals, by eavesdropping or absorption." Some of these images are very informal, and their simplicity is quiet and endearing. Others are more dramatic in tone or personality. They all have in common a naturalness that comes from Cartier-Bresson's working process. He does not create unusual effects through lighting or manipulating his subjects. He does not crop his images in printing. He is not much concerned with photographic techniques or gadgetry beyond their usefulness to his process.

In his portraits of Edmund Wilson and son, Truman Capote or the Alsop brothers, there is a clear understanding between the sitter and photographer, an understanding that must come from trust and respect. Cartier-Bresson seems to be moving through their lives, catching moments that are no more important than those occurring before or after. But he has, after all, found the right moment: These photographs mirror the relationship between Cartier-Bresson and the people in them. "For his sight, divested of superficial prejudice or preference, focusing itself on what is most essential in his subject, also reflects what is most essential in himself," concludes Kirstein.

Portraiture is the one domain of traditional painting that, during the past hundred years, has been almost entirely subsumed by photography. As modern painters began to work less from life and more from the imagination, photographers like Cartier-Bresson embraced the portrait because, he said, "we accept life in all its reality." This notion of working with what is real, coupled with a reverence for the painter's adherence to structure and craft, allowed him to translate the personalities of his subjects into images that are, in some ways, as much like paintings as photographs.

In his 1946 portrait of Joseph and Stuart Alsop, the brothers gaze together off into a distant, imaginary world where opinions collide with history. It's a jumbled composition filled with tension; the Alsops are unapproachable. The photographer is blocked by a table that looks as if it is tilted up in his face, creating a series of simplified flat planes and diagonal lines that evoke Picasso's early experiments in cubism. The subjects are pushed behind this barrier, frozen by a ghostly light.

When we think today about Henri Cartier-Bresson's photographs, we usually focus on the title of the American edition of his best-known book, "The Decisive Moment," published in 1952. Our critical understanding of this complex body of work is still colored by the notion that photography can document a conjunction of events at a given "decisive" instant, seizing on its ability to freeze time. "To me," Cartier-Bresson wrote in his introduction to this book, "photography is the simultaneous recognition, in a fraction of a second, of the significance of an event as well as of a precise organization of forms which give that event its proper expression.

"I believe that through the act of living, the discovery of oneself is made concurrently with the discovery of the world around us which can mold us, but which can also be affected by us. A balance must be established between these two worlds — the one inside us and the one outside us. As the result of a single reciprocal process, both these worlds come to form a single one. And it is this world that we must communicate."

By looking again at his portraits, we can reevaluate his meaning. He views this moment that his film is exposed to light as a revelation of a whole life or event, a symbol for the passage of time. It's not a static impression, but one that is fluid, constantly changing. That moment is, after all, the instant that the past becomes present, and the present is where Cartier-Bresson prefers to situate himself.