(CNN) -- Twelve photographers from four continents have been shortlisted for the fourth Prix Pictet award in photography and sustainability. This year's theme of "Power," has "enormous breadth, embracing contradiction and paradox in equal measure that has uncovered images and issues that are both awe-inspiring and disturbing," organizers say. The aim of the award is to use the power of photography to raise public awareness of the social and environmental challenges of the new millennium. The winner will be announced by Kofi Annan, the awards' honorary president, in October at the opening of the finalists' exhibition of the shortlisted works at the Saatchi Gallery in London. The exhibition runs from the 10th to the 28th of October 2012.
Annual Prix Pictet photography prize announces shortlist . Competition designed to raise awareness of social and environmental challenges . Twelve photographers nominated; Winner will be announced by Kofi Annan in October .