WilliamEwing, director of Lausanne's Musée de l'Elysée photography museum, tells swissinfo why the human face has formed the centrepiece of his new book.
Ewing says that photo portraiture has undergone three phases: close likenesses, the face as the window on the soul and the start of a new era of discovery in photography.
WilliamEwing: This is certainly due to a combination of circumstances.