David Hockney says photographs misrepresent war. “For a New York exhibition, Hockney has made a watercolour based on Picasso’s painting ‘Massacre in Korea’. He has called it ‘Problems of Depiction’ and added a note which suggests that both the Picasso and this new spin on it are ‘a painter’s response to the limitations of photography, limitations that are still with us, and need some debate today’.”