Mike Abrahams's photograph of starving Romanian orphans in 1990, taken after the collapse of the Ceaucescu regime, is one of the "photographs the public weren't supposed to see" included in Underexposed, a collection initiated by Index on Censorship. In the same section are images smuggled out of China of the executions of pro-democracy demonstrators and a picture of a prisoner minutes after execution by electric chair which has never appeared in print in the US.
In another set of images, which did reach the reading public, "censorship in action" is itself the subject: there are scenes of book-burning in Nazi Germany, the Red Guards' destruction of Confucian shrines during the Cultural Revolution and civil rights protests in the southern United States (at which the US flag was banned because it was associated with support for racial integration).
Scenes of war from Roger Fenton's rose-tinted "Postcards from the Crimea" to Gilles Peress's Bosnian body bags in 1994 take in the horrific, the uncanny and the strangely calm.
A final section reminds us that misreading or misrepresentation of pictures is as much a hazard as suppression.