Tracing the origin of graphic war photography

Every day we are bombarded with images of violence and conflict. And every day we have to judge which are acceptable as legitimate journalism, which are propaganda and which are merely voyeurism.

A new exhibition at the National Portrait Gallery in Washington, DC, shows these questions are not new.

In 1862 Alexander Gardner, a commercial photographer, packed his camera and darkroom into his "war wagon" and travelled to view the aftermath of Sharpsburg.

There, 23,000 Americans had been killed, wounded or missing in the worst single day of fighting of the US Civil War. The photos Gardner took were shown in a New York exhibition called The Dead of Antietam.

"They were a galvanising, shocking moment for the public at the time," says National Portrait Gallery senior curator David Ward.

The largest display of photographs by Gardner are now being shown at the gallery as part of exhibition Dark Field of the Republic.

Jane O'Brien takes a look.

Filmed by Maxine Collins, edited by Bill McKenna