Bettmann lives on through the archive bearing his name. In 1981 it was sold to the Kraus Organisation, whose founder, Hans Peter Kraus, had a career which almost paralleled Bettmann's, fleeing Germany in 1939. In 1995 Kraus sold the collection - expanded from three to 15 million images by the addition of the United Press International archive - to Corbis, a subsidiary of Microsoft.
The current archive is part of Bill Gates's drive to establish a lucrative online database of the world's most influential images - a modern equivalent, says Corbis, of the ancient library at Alexandria. The idea is not only to make Bettmann's pictures more accessible to big commercial clients, but also to zap them into people's homes. You want to put that famous print of Marilyn Monroe with her skirt blowing up on your kitchen wall? Feel free - for a fee.
When the Microsoft deal went through, Bettmann was well into a long and extraordinarily active "retirement" in Florida (in 1983 he even had a small part in the Dudley Moore film Lovesick, playing that cliche, the East European emigre psychiatrist). Bettmann declared himself "delighted" with Bill Gates's plans. Prior to this - surprisingly - Bettmann had shown himself to be a rather reluctant apostle of the so- called visual age. "I do not welcome," he said in an interview in 1978, "the enormous emphasis on the picture. It is a flattening-out of history. The picture can never describe what the word can. The word lassoes the thought. The picture makes the observer an immediate participant in the event, but the meaning in the event lies in the word." Bettmann remained devoted to "the word" throughout his life, from the University of Leipzig where he gained his doctorate, to the Florida Atlantic University where he was associated with the book department in the Nineties. He also wrote extensively, including a book for the Library of Congress on the joys of reading.
Bettmann was moved more by pictures of things worth remembering than by pictures that were merely worth seeing. Even though the archive has expanded far beyond anything that can be attributed to a single vision, at its heart is a rarely erring feeling for images that might last. Bettmann organised it along thematic and generic lines. This, he said, was the secret of its success, because it suited the needs of picture editors who called on it to illustrate articles. The section "Firsts", for example, includes a photograph of Yuri Gagarin, the first man in space, a Durer etching of Adam and Eve and a photograph of Elizabeth Taylor's first wedding, to Nicky Hilton. The section "Ears" includes Spock and an adolescent Prince Charles.
"He developed his own idiosyncratic indexing, which is still in use," recalls Herbert Gstalder, president of Kraus. "He claimed it had the same construction as Bach. He was a Bach expert. That was one of the reasons he sold up, to devote himself to Bach - and writing." Gstalder never penetrated the Bach reference - probably a Bettmann joke - but he remains in awe of the man. "He was a great editor, he was ruthless. He had an eye for images that carried the human element of the story, and humour, there's a lot of humour in there."
The archive is full of historical resonances. Many of the images have come to symbolise and shape how we view key events: Lenin in Red Square ... St Paul's Cathedral surrounded by fire during the Blitz ... Churchill with Roosevelt and Stalin at Yalta. Bettmann's sense of photographs as illustrations - and not substitutes for more subtle and detailed texts - is crucial. A pictorialist might have been more concerned with the shape of Stalin's cap than with the expression on his face, might have missed the presiding formality of the occasion, which neatly summarises the tension invading this stiff get-together between inimical world views.
Bettmann's archive also powerfully captures the eccentric extremes of human behaviour: an airborne motorcycle stunt rider; a boy with three legs; the sausage charmer (she is blowing a pipe, Indian-style, as a string of sausages rises into the air). What on earth is a boy doing with a clothes' peg on his nose? What possessed a man to build a telephone receiver into his shoe? These are questions to which there may be no answers, but we have to be grateful to the presiding spirit that decided not to ignore them. Ever seen an albino hedgehog? Now's your chance.
One alarming thing happens towards the end of the current Bettmann archive catalogue: colour. These photographs, many of which post-date Bettmann's involvement, seem less strange, less artful. We see a woman standing in a purple kitchen; a camper van painted like a Lego toy; a vibrant collection of native head-dresses; a canopy of eye- catching umbrellas. In each case, colour seems to have been both the pretext and the point of the photograph. As a result, the pictures carry no more than an aesthetic charge. They would lack all interest in monochrome. This is what photographers mean when they say that black and white is more demanding: there has to be something else going on apart from the colour.
Black and white is undoubtedly the forte of the Bettmann archive, and, whatever you think of Bill Gates, thanks to him it is now available for everyone, a lasting monument to one man's vision. "I think he was thrilled about Bill Gates," says Gstalder. "He enjoyed having his name connected with him. Bettmann was a charming man, a Renaissance person, and he was responsible for some truly iconic images"