In Frame, four sets of measurements are made with a six-inch ruler. In the first, the rectangle of the camera is placed at an angle, and the trapezoid measured and perceived untrue from the camera viewpoint. In the second, the camera is placed at an angle, and the trapezoid measured is perceived as a rectangle. Although one views the measurement of a totally white frame, it is in fact the angle of the camera to the wall which is being measured. Thus, at the end of the sequence the measurements spell out a trapezoid. In the third, the rectilinear window frame is measured as a rectangle but perceived as a trapezoid. In the fourth, the film image of the window is measured as a trapezoid but perceived as a rectangle (the reverse of the second image).