The physical role of a photographer is to take pictures, to stay behind the lens.
Often photos are anonymous; they have a name attached but rarely a face or voice.
This video allows us to meet James Nachtwey, not his camera, and to hear about the photographs from the man who took them.
Nachtwey made this speech in 2007 to accept the TED prize.
In conjunction, he was given $100,000 to carry out one wish to change the world.
That wish, was to introduce the world to extremely drug-resistant tuberculosis (XDR-TB), an advanced form of tuberculosis affecting 1000s of people in countries all over the world.
XDR-TB is caused by a misuse of tuberculosis medicine or a lack of TB medicine altogether. In developing countries this is a major health problem that is being almost completely overlooked.
Witness 