This image of a leaf was released Thursday by Sotheby's auction house in New York. The work is a photogenic drawing that was thought to have been made in 1839, but now experts believe it could have been made as early as 1790.

New York ? Sotheby’s auction house is selling a primitive photograph that could be a much earlier work than originally believed. If so, Sotheby’s says, it would be one of the most important discoveries in the history of photography.

“Leaf,” to be sold at Sotheby’s on April 7, is a photogenic drawing – a cameraless process in which an object is placed on silver nitrate-coated paper or leather to form a negative image.

It had previously been attributed to William Henry Fox Talbot, considered the father of photography along with Louis-Jacques-Mande Daguerre. It was thought to have been made in 1839 at what is widely accepted as the dawn of photography.

But Sotheby’s says research by a leading photo expert suggests otherwise, that several early photo experimenters could be the authors, including Thomas Wedgwood, James Watt and Humphry Davy, who worked in the medium decades earlier. If that theory is true, it means the photo could have been made as early as 1790.

What it will fetch at auction is anyone’s guess, said Denise Bethel, Sotheby’s director of photography.

“The range is pretty wide,” she said. “When we thought it was Talbot, we gave it a $100,000 to $150,000 estimate. Now with this other possibility … it’s certainly far more valuable.”

Sotheby’s catalog lists “Leaf” as “Photographer Unknown.” But the auctioneer says an inscription of the initial “W” on the corner of the photo could point to Wedgwood or Watt as possible authors. Wedgwood died in 1805; Watt in 1819.

“Leaf” was among six similar anonymous works that were sold individually at Sotheby’s London in 1984. It was purchased by a dealer for $776, and only later attributed to Talbot.

Two of the other six works are now in the J. Paul Getty Museum in Los Angeles and one is at the Metropolitan Museum of Art in New York.

All six photogenic drawings were contained in an album belonging to Henry Bright of England, whose family had a close social connection to the Wedgwoods, Watt and Davy, adding further support to the theory that “Leaf” could be by one of them, Sotheby’s said.