Special filters that cause different colors to appear at different depths
Red objects appear close; blue objects appear distant
Physiological effect discovered by astronomer Carl Pulfrich.
Images viewed through a darkened lens reach the brain slower than those viewed through a clear lens.
Pulfrich effect glasses have one dark lens and one clear lens.
When something moves across the visual field, the brain fuses
two images from slightly different times.
Motion is thus converted into stereo parallax.