The world's earliest photograph is set to make more than £500,000 at auction.

The grainy image of a boy leading a horse was taken by French photographic pioneer Joseph Niepce in 1825.

The 6in by 4in photo is due to be auctioned by Sotheby's in Paris.

Philippe Garner of Sotheby's said: "This image and its accompanying correspondence oblige us to rewrite those crucial first stages of the history of photography."

It was previously thought he produced the first permanent photograph in 1826.

Niepce created his photo of an engraving using a technique called heliography, where light is used to project an image on to a photo-sensitive surface.

The photo lay undiscovered in a French collection until recently without its significance being realised.

Story filed: 11:52 Thursday 17th January 2002