The darker reaches of the human soul had meaning when Brassai was making his most famous photographs--the early '30s when Freud was serving up naked lunches of id meat, when surrealism draped the crutches of reality with the melting watches of nightmare, when Peter Lorre scuttled through the movie "M" as a child molester flashing the whites of his eyes at the vaulting shadows of film noir, and young men and women in search of adventure and authenticity found it in the neighborhoods of crime, vice, drugs and lowlife.

Now, of course, the real horror is not meaning but meaninglessness-- motiveless movie monsters, the desecration of the Madonna at the Brooklyn Museum of Art.

There's another difference: When Brassai took his camera out into the Paris night, he was reveling in the humanity-- not the alienation--of the whores, thieves and gay demimonde he photographed: the naked brothel staff with dimpled bodies whose shapes remind you of Babe Ruth, the lurking darkness beneath bridges, the cafe girl with spit curls and a bad tooth lolling heavy-lidded between two sailors, the quarreling lovers in their adamance and sulk, the two thugs of the sort who robbed and beat Brassai during his nighttime investigations.

He's not a voyeur or an exhibitionist--so many 20th-century artists are one or the other. Instead, he's what the French call a flaneur, a spectator, a man who finds his satisfaction in observing the public scene. He doesn't reveal things because they are already revealed. Like some sort of perfect husband, he takes the world for granted and loves it madly at the same time.

The ultimate cosmopolitan, Brassai (a pseudonym taken from his Hungarian home city of Brasso) is surprised by nothing and fascinated with everything in these 113 images at the National Gallery of Art. Even darkness itself has a weight of its own in a silhouette of Saint-Germain-des-Pres rising over the meager lights of the Cafe des Deux Magots or the rooftops of Paris beneath the fairy lightness of the distant Eiffel Tower.

To take pictures of darkness, Brassai had to take pictures of lights as well--the muzzy lamps along the Pont Neuf, the lamp glowing over the bearded watchmaker, the gritty glow of light on wet paving stones. But unlike the photographic masters who captured light, Brassai saved his love for darkness.

He was born Gyula Halasz a hundred years ago. His father was a professor who loved Paris and took a very young Brassai there, a trip that left him with lifelong memories.

In World War I, Brassai fought against France and the Allies. Afterward, in the chaos of the postwar world's revolutions and redrawing of borders, he joined a number of other Hungarian writers and artists in Germany. He worked as a journalist and studied drawing and painting. He arrived in Paris in 1924, accomplished at the bohemian skills of ducking cafe bills, sleeping all day and rambling endlessly through Paris. He had big eyes on a sly face that reminded people of a turtle. He was famously charming.

He wrote to his parents about his early days in Paris: "Could I have done anything wiser in the first few months than to do nothing? . . . There is, indeed, an abundance of things that demand one's attention here, particularly for a person like me, who is intrigued by every particle of this living monster, its outside, its inside, the way it breathes, lives, and moves."

He had the animist's knack for seeing life in everything--bridges, chimneys, a cast of Picasso's hand, graffiti, a cobblestone, whatever.

In 1930, after years of despising photography, he began taking pictures under the name of Brassai--he saved "Halasz" for the paintings, which are forgotten now.

He recalled: "How I became interested in photography reminds me of a story Isadora Duncan once told me." It seemed Duncan had an accompanist she detested. He played well for her dancing, but "his face drove her to such distraction that she had a screen placed between them when she practiced." Her hatred grew. One day they were riding across from each other in a carriage. "The carriage came to an abrupt stop and she was catapulted into his arms. She said to me, 'I stayed there; I understood it was to be the greatest love of my life.' . . . So too with me and the camera. I once detested her."

So he loved what he hated, hated what he loved. He animated the inanimate, he looked at high and low society with the same eye--in other words, he was the sort of threshold creature who is most comfortable being in two worlds at once, reconciling these contradictions by simply accepting them as the nature of the great genius world he saw around him.

He studied technique, and used an eccentric collection of plate cameras, even after the 35mm Leica became the chosen camera of photographers with similar interests. He didn't care about taking endless shots of the same scene, 35mm-style, feeling that if he limited himself to two or three exposures, his picture would seem less accidental and more his.

He posed his cafe pictures, having his subjects wait while an assistant set up a reflecting screen and then held the flash powder that exploded into light that produced softer edges than flashbulbs--and earned him the nickname "The Terrorist" from Picasso. He made reality into a stage set, then waited and waited until his subjects' attention wandered back to their cafe concerns, their nightlife personas. The powder erupted, the shutter of his Voigtlander camera clicked. In other words, he waited till the people stopped posing for the camera and resumed posing for the world. He took no interest in photographing the secret souls of his subjects--he found their true life in public poses.

Still, secrets arise. The young Salvador Dali is not the later madman ringmaster leaping about with waxed mustache--he looks like a guilty, arrogant young man wishing his mother would spank him for being bad. Picasso, the demigod of 20th-century art and a genius at looking like a genius, has an unsettling humanity here. On the other hand, Henry Miller and Jean Genet pose with their cigarettes and their penetrating writers' stares--dust jacket stuff.

Knowing events to come, you have a hard time not seeing degeneracy and horror when you look at "Lesbian Couple at Le Monocle, Paris," from 1932. A wistful woman in an evening dress cuddles against a woman in necktie and man-combed hair, identified later as Violette Moriss, a weightlifting champion who had a double mastectomy. During World War II, she collaborated with the Gestapo and tortured women prisoners. The Resistance killed her in 1944.

Brassai's first great success came with a book called "Paris at Night" in 1933. He planned another book, "Secret Paris," but it wasn't published until 1976 as "The Secret Paris of the 1930s." Meanwhile, he sold his prints to magazines and published other books.

As he moved out of his lowlife period, Harper's Bazaar hired him to shoot the high society of Paris. The challenge of high and low society were much the same. He wrote: "Entry into both these exclusive societies, made up primarily of the idle, is not easy. Each has its regulations, its customs and usages, its moral code, its affairs of honor. . . . Even the languages are similar, both tainted with snobbery."

In "Evening at Longchamp Racetrack," he records the beauty and desperate calm of the rich as he might have recorded the brutalities and calm desperation of the poor. He staged pictures of the rich just as he did with the poor. "Leaving the Opera" shows a couple drifting happily down a staircase, with geometric shadows mounting the steps behind them in black-and-white squares.

Brassai verged on the surrealistic with his plunges into the depths of the everyday world. He photographed a loaf of bread baked as a face and wrote: "What I love, and passionately, is to give to a 'worthless' object a value, by the simple act of discovering it." The bread, he said, was "the spitting image of French life: optimistic in spite of it all, limited to immediate pleasures, egocentric, gourmand."

If he seems to be condescending to reality here, consider another statement, derived from the realism of Goethe, whom he admired: "The world is richer than I."

In other words: Who was he to judge? He photographed whimsy and damnation, bridges and nudes with the same dark delight. He was not above little puns: a group of policemen in serious parley beneath a picture of a kitten; or nuns in Monaco with their vast headdresses erupting with the same exotic delight as the cactuses along their path.

His sunlit pictures demonstrate his amazed modesty in the face of the world: a vast outdoor staircase breathing with a saturnine eternity, or his picture of the farmland geometries of the Isere Valley proclaiming a triumph of the good earth.

Nowadays, Brassai is a hero of a lost world, a world of modernist sensuality and modesty in the face of reality. He savors the world with a bohemian joy that would be undermined by irony, alienation and the puritanism of postmodernism and political correctness.

Brassai died in 1984. His wife Gilberte, whom he married in 1948, lives on in Paris. The show runs through Jan. 16.

'BRASSAI: THE EYE OF PARIS'

"Brassai: The Eye of Paris," celebrating the centenary of the artist's birth, opens today at the National Gallery of Art and runs through Jan. 16. The museum is on Constitution Avenue NW between Third and Seventh streets. It is open Monday through Saturday, 10 a.m. to 5 p.m. and Sundays 11 a.m. to 6 p.m. Admission is free. For information call 202-737-4215.