Launched in New York in 1913, Vanity Fair rapidly became the most intelligent fashion magazine in the world: a beautiful, stylish window on the stars of the century's new movements in cinema, art, music, literature and science.

This irresistible exhibition follows portrait photography through its changes - technical and aesthetic - from small, hand-printed studio shots to today's complex operations with huge budgets.

Vanity Fair's first resident photographer, Edward Steichen, dominates the exhibition's early years, 1913-36. He was an exhilarating stylist who reveals in his lighting and compositions influences from modernist movements.

The show's early portraits offer fascinating insights into legends - a youthful Einstein, D H Lawrence and Chaplin, a surprisingly dandy James Joyce - but, inevitably, Hollywood dominates.

The surprisingly tender moments in Nickolas Muray's beach scene with Douglas Fairbanks Jr and Joan Crawford in 1929 is matched by Bruce Weber's collusion with playwright Sam Shepard and Jessica Lange, nose-kissing in a garden, more than half a century later.

The possibilities of colour explode in the late Thirties, with Steichen's tableaux at Radio City Music Hall.

His leaping dancers in acid-sharp colours pioneered the use of centrefolds. Once the magazine resumed publishing - it had ceased from 1936 to 1983 - there was a rebirth, with Annie Liebowitz assuming Steichen's role, and new epic scales and sophisticated scenarios.

Liebowitz's tableaux and themed groups (of big-shot directors and Hollywood legends) are intriguing, but elsewhere the magazine edges towards the risqué and erotic, with new surnameonly-celebrity photographers: Penn, Newton, Weber, Ritts, Meisel.

Mario Testino's shot (1997) of Princess Diana epitomises a perennial love of timeless elegance, while Liebowitz's pregnant Demi Moore was a deserving bestseller.

Balancing these are the occasional photojournalists acting as time-markers, like Jonas Karlsson's fire-fighters at Ground Zero, conflating glamour and heroism.

Representing the blatant art - historical line, Michael Thompson's Maja - with Julianne Moore naked on a bed amid sumptuous silks - is an irresistible reference to the great portrait painters who fill the galleries around this unmissable exhibition.

• Until 26 May. Information: 020 7312 2643, www.npg.org.uk