Ames Window

Adelbert Ames, Jr. designed approximately twenty demonstrations that probe the nature of depth perception. One of the most effective is what he named the “rotating trapezoidal window.” In its original form, the window was designed to be constructed as a thin - almost two dimensional - surface, painted on both sides to resemble a normal rectangular window when viewed from one orientation. It is actually made in the shape of a trapezoid with cutouts where glass might be and it includes appropriately painted shadows. The window is then placed on a pivot oriented perpendicular to its horizontal axis. When rotated slowly in one direction - and viewed either monocularly from a short distance or binocularly from a large distance - the window appears to oscillate rather than rotate about its axis. During its perceived oscillation, the window also appears to change size and shape.