Chiaroscuro translates from the Italian as “light-dark.” But such a definition fails to capture the depths of the term, which artists use to describe the treatment of light and dark within a composition. In his painted portraits John Singer Sargent masterfully renders light, shadow, and darkness. In the later years of his career, by switching mediums from paint to charcoal, he amplified the drama of chiaroscuro. The black-and-white portraits of this period, long overshadowed by the paintings, take the spotlight at the Morgan Library. —C.J.F.