When two become one: Adam Broomberg and Oliver Chanarin's ghostly 'scarti' images

In 2003, Adam Broomberg and Oliver Chanarin embarked on an ambitious project named Ghetto. For it, they travelled around the world taking photographs and interviewing inhabitants of 12 contemporary gated communities, from Tanzanian refugee camps to residents of the Rene Vallejo Psychiatric Hospital in Cuba.

The book is now out of print, but a new project by the Deutsche Börse Prize-winners revisits some of its imagery.

Scarti di avviamento is a term used by Italian printers for paper which is fed through a printing press to clean the ink drums between two prints. The developer can then be left with an image comprised of two different photographs merged together into one image. They look like the hand of a ghostly Photoshop.

These scraps are usually tossed aside, but Gigi Giannuzzi, the publisher of Broomberg and Chanarin's work on Ghetto, was wise enough to think otherwise. Before his death last December, Giannuzzi had stored them away for safekeeping. After his death, they were discovered in his files.

With characters superimposed over disparate scenes, the results are captivating. It's almost difficult to believe that they're accidental.

'Scarti' by Adam Broomberg and Oliver Chanarin is out now (Trolley, £45)