Photography is a powerful tool for documenting the fate of victims of crimes against humanity. Contrary to verbal testimony, which may have inadvertently changed over time or been deliberately manipulated, and which is subject to personal interpretation, a photograph is a direct registration of reality or, to be more exact, a slice of reality.

Of course, a photograph is never totally objective, subjected as it is to the choices and interpretations its creator decided to make. But it connects with a past reality in a way that verbal or textual testimony never does. For all the written testimonies about Nazi cruelties in World War II, the photographs taken of the concentration camps after their liberation have a historical directness that is impossible to convey verbally.

It was only with the introduction of fast and portable 35-mm cameras in the 1930s that photojournalists could travel with light and practical equipment to...