Method acting
The "Encyclopedia of World Biography" states that his films often featured actors who studied "Method acting", noted for portraying an earthy, introspective style. A leading example of such "Method" actors would be Al Pacino, who, early in his career, studied under Method acting guru Lee Strasberg. Lumet also preferred the appearance of spontaneity in both his actors and settings, which gave his films an improvisational look by shooting much of his work on location.