The events of the past few years, from 9/11 to the South Asian tsunami disaster, have once again shown us that despite round-the-clock news coverage, the Internet and multi-channel cable TV, the still image is as powerful as ever. Photography remains the ideal medium for capturing all aspects of human emotion, drama and tragedy. Witness features powerful and stirring images from the world's greatest photojournalists, as well as providing a history of the medium. Starting with some of the first key figures such as Roger Fenton, who photographed the Crimean war with a bulky large format camera, it moves on through the decades covering defining events in our history from the Great Depression, to space missions, the dismantling of the Berlin Wall and the recent Iraq war.