Carlos Reygadas's Silent Light, a big hit on the international festival circuit, is a long, slow, delicate portrait of a farming family from the Mennonite community who live an austere, religiously observant life in northern Mexico. Protestants in a Catholic country, they speak an old-fashioned form of German. They first settled there in the 1920s, moving down from the United States and Canada, and unlike similar communities in Pennsylvania they don't eschew mechanised vehicles and buttons. I'd like to have learnt more about their history and values, but Reygadas, working with a non-professional cast, has chosen to look in a very plain manner at the husband's obsession with a younger woman and its destructive effect on his marriage.