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This is the 'big' version of the second animation of the two on the
'Animated Explanations' page. It has been implemented with finer graphical
and temporal resolution than the smaller version.
The view is from above, as though looking down on the experiment from the ceiling.
Again, the upper target is shown oscillating back and forth, as the filled circle. The lower target, which is set by the observer to P'N or P'F to match the apparent Pulfrich distance, is not shown.
The filled circle shows where the observer would localize the target without any filter. The typical "personal equation" (localization error) is not shown.
The unfilled circle shows the illusion--how the observer with the Pulfrich filter in front of the left eye would locate the target.
If the target motion were simple harmonic (sinusoidal), then the path would be an ellipse, as viewed from above, not the flattened curve shown in this animation.
The Pulfrich Effect, SIU-C. Last updated 2000-07-23