Saltwater, gold leaf and 19th-century chemistry: the world's longest-running photography exhibition is back, and it's more technically adventurous than ever

Four children in homemade superhero costumes with box-like masked heads and trailing fringes stand on rubble in a roofless brick ruin overgrown with plants.

More than 5,200 photographers entered. Just 48 made the cut. That's a success rate of less than one per cent. Which makes getting a place in the Royal Photographic Society's International Photography Exhibition feel more like getting into an Ivy League university than entering a photography content.

But IPE167, which opens at London's Saatchi Gallery on August 7 and runs until September 11, is far more than a competition. Now in its 167th consecutive year, it's the world's longest-running photography exhibition, and it's as vital as ever.