A New Trick for Pulfrich Stereoscopic 3D Video
StereoscopyNews.com reports that the Pulfrich effect is a psycho-optical phenomenon that was documented by Carl Pulfrich in the early 20th century. It is due to the difference in the speed of perception according to an object’s luminosity. The Pulfrich effect is thus perceptible only in the case of moving objects. For example, look at the movement of a pendulum swinging from left to right. If you cover one eye with a piece of dark glass you will see the lateral swing seconded by a movement in depth, as if the pendulum were oscillating in a circle rather than a plane. The darker the filter, the more pronounced the effect becomes.
If the filter is over the left eye, the moving object seems to be in front of the plane of the screen if it moves to the left and behind the plane if it moves to the right. The explanation is simple: The presence of a dark filter over one eye produces a lag in the perception of the scene coming from this eye. The left eye thus sees the pendulum a split-second later, and that causes a horizontal disparity with respect to the right eye. The brain interprets this difference as an interocular parallax and deduces a depth proportionate to the speed and direction of the moving object. Motionless objects are not affected.