Mary Ellen Mark: 25 Years

You won't find any celebrities here, but you won't miss them. In her 25 years, Mary Ellen Mark has photographed people she describes as "unfamous," by which she means people who have not cultivated a public face. And while many of her subjects come from the lower depths — heroin addicts in Britain, mental patients in Oregon — do not compare her to Diane Arbus; the pictures in Mary Ellen Mark: 25 Years are neither exploitative nor sentimental. A