Chuck Close, a painter famous for his huge canvases and his uncanny ability to portray his subjects with almost photographic realism. He has a neurological condition that prevents him from recognizing people's faces. Today, Chuck Close is in his early 70s - still painting, with brushes strapped to his hand - and now the subject of a biography by his friend Christopher Finch. Close and Finch talked with Steve Paulson about Close's painting career