Interference filter technology
Imagine a camera which starts at position X and moves right to position Y as shown by the arrow. If a viewer watches this segment with a dark lens over the left eye, then when the right eye sees the image recorded when the camera is at Y, the left eye will be a few milliseconds behind and will still be seeing the image recorded at X, thus creating the necessary parallax to generate right and left eye views and 3D perception, much the same as when still pictures are generated by shifting a single camera. The intensity of this effect will depend on how fast the camera is moving relative to the distance to the objects; greater speed creates greater parallax. A similar effect can be achieved by using a stationary camera and continuously rotating an otherwise stationary object. If the movement stops, the eye looking through the dark lens (which could be either eye depending on the direction the camera is moving) will “catch up” and the effect will disappear. One advantage of this system is that people not wearing the glasses will see a perfectly normal picture.
Of course, incidental movement of objects will create spurious artifacts, and these incidental effects will be seen as artificial depth not related to actual depth in the scene. Unfortunately, many of the applications of pulfrich involve deliberately causing just this sort of effect and this has given the technique a bad reputation. When the only movement is lateral movement of the camera then the effect is as real as any other form of stereoscopy, but this seldom happens except in highly contrived situations.
Though pulfrich has been used often on TV and in computer games, it is rarely if ever used in theatrical presentations.
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Tags: Arts and Entertainment, Business, Camera, Cameras and Camcorders, Parallax, Photography, Shopping, Television