The French photographer Robert Doisneau once said that he had done just three seconds of useful work in 50 years.
In a fraction of one of those seconds he produced one of the world's most admired, reproduced and imitated romantic photographs: a picture of two lovers kissing outside the Paris town hall in 1950.
The photograph - Le Baiser de l'Hôtel de Ville - is tucked away casually amongst 280 other Doisneau images in a free exhibition which began yesterday at, appropriately, the Paris town hall.
Doisneau, who died in 1994, aged 81, would presumably have approved of the decision to treat his most reproduced image as just a small part of his work. He came to hate the "kiss" photograph, which caused him legal problems late in his life and (baseless) accusations of cheating by using actors. He made it clear from its first publication in Life magazine in 1950 that the picture was posed - but that the couple were genuine lovers who he had encountered on the street.
The Doisneau exhibition, "Paris en liberté", which lasts until 17 February, is laid out like an urban ramble through the Paris of the 1950s and 1960s (with some later shots). The show, the largest Doisneau retrospective for 11 years, has been curated by the photographer's daughters, Francine Deroudille and Annette Doisneau.
Despite their father's exasperation with the "town hall kiss" picture, they have presented one of the last remaining original prints, which is worth over €150,000 (£100,000) to the mayor of Paris, Bertrand Delanoe. Doisneau has come to be regarded as a romantic photographer, but he saw himself as a realist: a brutal thief of images, mostly taken in the unfashionable areas of the Paris of the day.
"An intelligent photographer is done for," he once commented. "He has to be stupid, a poacher, a pick-pocket. And to have a rough love of life."
Doisneau also said that of the tens of thousands of photographs he took, only 300 had been successful. Since each one took a hundredth of a second to make, that meant, he claimed, that he had done only "three seconds of successful work in a career spanning 50 years".
Parts of Doisneau's Paris are still in existence. Other parts - the Paris of the Halles wholesale food market and cobbled working class streets - have been overlaid by official vandalism, touristification and gentrification. The exhibition is, whatever Doisneau's original intentions, an ode to a lost city.