Persistence of vision explains many of the effects described in Techniques of the Observer. It is a consequence of iconic memory (the type of memory that "takes snapshots of reality"). This phenomenon, causes afterimages (when an image is still seen after no longer being physically present) that last a couple of seconds. A modern example of this, can be seen in the image below where LEDs move so rapidly so as to create the image of a whole when in reality, they are moving in rapid succession. The discovery of P.O.V. led to a change in the production of media which culminated in the 20th century with very realistic film and animation.