The celebrated Renaissance artist's watercolors, drawings and prints — many lent by the Albertina Museum in Vienna — are the focus of a new exhibition at the National Gallery in Washington. It is rare for a museum to lend the heart of its most prized collection to another museum, but the Albertina in Vienna has done just that by shipping almost a hundred watercolors and drawings by Albrecht Dürer to the National Gallery of Art here for an exhibition. Dürer, a German born in Nuremberg in 1471, is the great master of the Northern European Renaissance, akin to Leonardo da Vinci, Raphael and Michelangelo of the Italian Renaissance. Dürer's greatness, according to Andrew Robison of the National Gallery, curator of the show, is based on his watercolors, drawings and prints, just as Da Vinci and Raphael are identified with painting and Michelangelo with sculpture...