Use in Stereoscopy
The Pulfrich effect has been utilized to enable a type of stereoscopy, or 3-D visual effect, in visual media such as film and TV. As in other kinds of stereoscopy, glasses are used to create the illusion of a three-dimensional image. By placing a neutral filter (e.g., the darkened lens from a pair of sunglasses) over one eye, an image, as it moves right to left (or left to right, but NOT up and down) will appear to move in depth, either toward or away from the viewer.
Because the Pulfrich effect depends on motion in a particular direction to instigate the illusion of depth, it is not useful as a general stereoscopic technique. For example, it cannot be used to show a stationary object apparently extending into or out of the screen; similarly, objects moving vertically will not be seen as moving in depth. 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. It can, however, be effective as a novelty effect in contrived visual scenarios. One advantage of material produced to take advantage of the Pulfrich effect is that it is fully compatible with "regular" viewing without the need for "special" glasses.
The effect achieved a small degree of popularity in television in the late 1980s and 1990s. On Sunday, January 22, 1989 the Super Bowl XXIII halftime show and a specially produced commercial for Diet Coke was telecast using this effect. In the commercial, objects moving in one direction appeared to be nearer to the viewer (actually in front of the television screen) and when moving in the other direction, appeared to be farther from the viewer (behind the television screen). Forty million pairs of paper-framed 3D viewing "glasses" were distributed by Coca-Cola USA for the event (though they were originally produced and intended for a May 1988 3D episode of Moonlighting (TV series) that never finished production due to a writer's strike). The right eye's filter was a rather dark neutral gray while the left was transparent. The commercial was in this case restricted to objects (such as refrigerators and skateboarders) moving down a steep hill from left to right across the screen, a directional dependency determined by which eye was covered by the darker filter. The commercial was said to be created using Nuoptix 3D technology to create the Pulfrich effect.
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