HAD YOU BEEN in Paris between 1854 and 1870, somebody gifted and accoplished far beyond the ordinary, you would sooner or later have entered a handsome new building at 35 Boulevard des Capucines across whose facade was inscribed a large, gauzy approximation of a signature - "Nadar" - at night, illuminated by gas. An archetypal elevator would have taken you to the fourth floor, where you would have entered a studio painted and furnished entirely in red. The proprietor, a giant with flaming red hair and moustaches, dressed in red wool robe, would have embraced you, put you at ease, and studied you with round, shining blue eyes.

This was Felix Tournachon, called Nadar, an eccentric polymath born in 1820 who had tried his hand at medicine, journalism, caricature, cartooning, novels, memoirs, espionage, and was yet to be renowned as a ballonist. With greater singlemindedness, he was a photographer: the first to take pictures by artifical light, in the sewers and catacombs, the first to take aerial photographs, in 1858 from a balloon; above all, a portrait photographer. His subjects were his friends and the friends of his friends, inhabitants of a community of creative people at the boil, living at close quarters in what was the cultural capital of the earth. Nadar was a member of this high-spirited society, and its recorder.

The first photograph, a dim glimpse of a roof, had been taken in 1827; by 1854, when Nadar set up his studio, the daguerreotype and the calotype had already had their day; the process he learned was the cumbersome "wet-plate" technique. The deft handling of the glass, sweeping the collodion over it in one sure gesture, while keeping the sitter quiet and at ease during the long exposure, controlling the wavering light with shades and reflectors, all presented a heroic challenge.

That so volatile a personality as Nadar became a master is strange. An old friend had complained of his irrational enthusiasms: "wanting to do everything, taking on everything - and then always losing interest and giving up." Yet his portraits are a triumph of patience and skill, and better, a testimonial to his talent for friendship. To all he was "le bon Nadar," and his friendship, both faithful and practical, supported several men after fashion forgot them. Compassion and respect, united with what his caricaturist's eye picked out, made him the artist he was. Anyone can learn the theory of photography, he said, but a feeling for the nuances of light and how to use them can't be learned, nor can "that instant understanding which puts you in touch with the model quickly" - and alone makes possible "a really convincing and sympathetic likeness, an intimate portrait."

In spite of his personal flamboyance, he shrank from photographing people who made a cult of themselves - actors, soldiers and politicians; women too, for that matter. When he did find someone unsympathetic in front of the camera, he astutely let him betray himself. Courbet, whose painting and personality were both distasteful to Nadar, sprawls defiantly, fist on cheek, hard dark eyes expressing exasperated tedium.

Eighty of the best "intimate portraits" appear in this bountiful book, with a felicitous text and notes on each subject by Nigel Gosling, one-time art editor of the London Observe. Most are reproduced from original negatives, and while they lack some of the subtlety of tone perceptible in original prints now on display at the Metropolitan Museum, they are the original size and at least suggest the delicate texture and haunting immediacy of the originals.

Baudelaire, a beloved friend whom Nadar visited regularly long after he could no longer speak, was photographed in his prime in 1855, overcoat collar turned up, handsome, clean-shaven, derisive face slightly averted while the eyes grapple with the lens as if if were a mirror. Daumier stands in darkness in a dark cloak, his sensitively lit head underlined by collars of white linen and black velvet. He frowns, and the Goncourts' cruel description fits the image: "two very black, small eyes, a little nose shaped like a potato, a large man with a sharp voice and nothing kind nor open in his expression." But Nadar loved him, organized a show of his work when he was blind, dying, and forgotten, and the photograph has the grave beauty and penetration of a Rembrandt.

When Nadar photographed George Sand, godmother to his son Paul, she was 60; she wears a bugled silk dress that would look better hung at a window than on a woman, but her dark-eyed belle-laide's face outshines it. The Goncourts wrote of her "eating late suppers, drinking champagne, fornicating and carrying on like a forty-year-old student," but she was sensible and generous too. "Stick to your portraits!" she told Nadar when he became obsessed with balloons, and offered to sit for him all day long if it would be of use.

There is Manet, earnest and sincere; Dumas pere beaming with affection and kindness, Dumas fils , skeptical and reserved; the wunderkind Dore, bursting with confidence, in checked pants and scarf, and coat that has lost a button; Bernhardt, aged 22, with a mop of kinky hair, flawless skin, and eyes that gaze unblinkingly into the light.

The 1870 war ended many careers, and for Nadar, who had been financially ruined by his balloonign, the need to recoup, and perhaps too a sense of the light having gone out, put an end to the idea intimate portraits. With his son Paul he went commercial, very successfully. Many impeccable likenesses taken during the later years of the Atelier Nadar (it finally closed only in 1939) are here - Monet, Verne, Turgenev, Liszt, the Prince of Wales, the abounding de Lesseps family, and a fat young man with thick curls who seems to hold a small dummy on his knee - Pablo Casals and his accompanist Harold Bauer. One of the treasures of this period is the world's first photo-interview: Nadar talking to a famous centenarian, lively as a cricket, phototographed by Paul and recorded by a stenographer.Nadar outlived all his friends and died in 1910, almost 90.

It's interesting to compare him to Julia Margaret Cameron, roughly his contemporary, to whom some half-dozen expensive books have recently been devoted; this is Nadar's first. Both photographed famous men. Cameron took up the camera at 50 and never bothered to master its use. She was a dynamic original, heedless of difficulty, who imposed her own vision of greatness on her sitters. She was after the soul, but there is a sameness about what she found: spectral, anxious, brooding figures, hands clutching a cloak to the breast, profiles and silver locks ethereally alight. To turn from these dramatic likenesses to the relaxed gravity of Nadar's portraits is to turn from a trobbing, hectic individual expression to a society of men, dressed in their own clothes, united by devotion to their own art and familiarity with one another's. Intimate as Nadar's art is, it's social communicative patient, and delicately receptive, as men must be to live together.