In film and video production, split screen is the visible division of the screen, traditionally in half, but also in several simultaneous images, rupturing the illusion that the screen's frame is a seamless view of reality, similar to that of the human eye. There may or may not be an explicit borderline. Until the arrival of digital technology, a split screen in films was accomplished by using an optical printer to combine two or more actions filmed separately by copying them onto the same negative, called the composite. In filmmaking split screen is also a technique that allows one actor to appear twice in a scene. The simplest technique is to lock down the camera and shoot the scene twice, with one "version" of the actor appearing on the left side, and the other on the right side. The seam between the two splits is intended to be invisible, making the duplication seem realistic. Influences An influential arena for the great split screen movies of the 1960s were two world's fairs - the 1964 New York World's Fair, where Ray and Charles Eames had a 17-screen film they created for IBM's "Think" Pavilion (it included sections with race car driving) and the 3-division film To Be Alive, by Francis Thompson, which won the Academy Award that year for Best Short. John Frankenheimer made Grand Prix after his visit to the 1964 New York World's Fair. The success of these pavilions further influenced the 1967 Universal exhibition in Montreal, commonly referred to as Expo 67, where multi-screen highlights included In the Labyrinth, hailed by Time magazine as a "stunning visual display," their review concluding: "such visual delights as Labyrinth ... suggest that cinema—the most typical of 20th century arts—has just begun to explore its boundaries and possibilities," as well as A Place to Stand, which displayed Christopher Chapman's pioneering "multi-dynamic image technique" of shifting multiple images. Directors Norman Jewison and Richard Fleischer conceived their ambitious split-screen films of 1968 after visiting Expo '67. It's also common to use this technique to simultaneously portray both participants in a telephone conversation, a long-standing convention which dates back to early silents, as in Lois Weber's triangular frames in her 1913 Suspense, and culminating in Pillow Talk, where Doris Day and Rock Hudson share a party line. So linked to this convention are the Doris Day/Rock Hudson movies that Down With Love, the only slightly