Pulfrich effect
Encyclopedia
The Pulfrich effect is a psychophysical
percept wherein lateral
motion of an object in the field of view is interpreted by the visual cortex
as having a depth component, due to a relative difference in signal timings between the two eyes.
, optic neuritis
, or multiple sclerosis
. In such cases, symptoms such as difficulties judging the paths of oncoming cars have been reported. The phenomenon is named for German physicist Carl Pulfrich
, who first described it in 1922. The effect has been exploited as the basis for some television, film, and game 3D presentations.
The Pulfrich effect has typically been measured under full field conditions with dark targets on a bright background, and yields about a 15 ms delay for a factor of ten difference in average retinal illuminance. These delays increase monotonically with decreased luminance over a wide (> 6 log-units) range of luminance. The effect is also seen with bright targets on a black background and exhibits the same luminance-to-latency relationship.
, 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. 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, Jan. 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 refrigerator
s 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.
charity special Dimensions in Time
and in dream sequences of the 1997 3rd Rock from the Sun
two-part season 2 finale Nightmare on Dick Street. In many countries in Europe
, a series of short 3D films, produced in the Netherlands
, were shown on television. Glasses were sold at a chain of petrol stations. These short films were mainly travelogue
s of Dutch localities. A Power Rangers: Lightspeed Rescue
movie called Power Rangers in 3D: Triple Force (later broadcast as two-part Trakeena's Revenge) sold on VHS through McDonalds purportedly used "Circlescan 4D" technology, which is based on the Pulfrich effect, but there was very little 3D present. In the United States and Canada, six million 3D Pulfrich glasses were distributed to viewers for an episode of Discovery Channel
's Shark Week
in 2000. Animated programs that employed the Pulfrich effect in specific segments of its programs include Yo Yogi, The Bots Master
, and Space Strikers
; they typically achieved the effect through the use of constantly-moving background and foreground layers.
The videogame Orb-3D
for the Nintendo Entertainment System
used the effect (by having the player's ship always moving) and came packed with a pair of glasses. So did Jim Power: The Lost Dimension in 3-D
for the Super Nintendo
, using constantly-scrolling backgrounds to cause the effect.
Psychophysics
Psychophysics quantitatively investigates the relationship between physical stimuli and the sensations and perceptions they effect. Psychophysics has been described as "the scientific study of the relation between stimulus and sensation" or, more completely, as "the analysis of perceptual...
percept wherein lateral
Lateral
Lateral may refer to:*Lateral , an anatomical direction*Lateral canal, a canal built beside another stream*Lateral consonant, an ℓ-like consonant in which air flows along the sides of the tongue...
motion of an object in the field of view is interpreted by the visual cortex
Visual cortex
The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....
as having a depth component, due to a relative difference in signal timings between the two eyes.
Overview
The effect is generally induced by placing a dark filter over one eye but can also occur spontaneously in several eye diseases such as cataractCataract
A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light...
, optic neuritis
Optic neuritis
Optic neuritis is the inflammation of the optic nerve that may cause a complete or partial loss of vision.-Causes:The optic nerve comprises axons that emerge from the retina of the eye and carry visual information to the primary visual nuclei, most of which is relayed to the occipital cortex of the...
, or multiple sclerosis
Multiple sclerosis
Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...
. In such cases, symptoms such as difficulties judging the paths of oncoming cars have been reported. The phenomenon is named for German physicist Carl Pulfrich
Carl Pulfrich
Carl Pulfrich was a German physicist, noted for advancements in optics made as a researcher for the Carl Zeiss company in Jena around 1880, and for documenting the Pulfrich effect, a psycho-optical phenomenon that can be used to create a type of 3-D visual effect.-External links:...
, who first described it in 1922. The effect has been exploited as the basis for some television, film, and game 3D presentations.
Demonstration
In the classic Pulfrich effect experiment, a subject views a pendulum swinging in a plane perpendicular to the observer's line of sight. When a neutral density filter (a darkened lens—typically gray) is placed in front of, say, the right eye the pendulum seems to take on an elliptical orbit, appearing closer as it swings toward the right and farther as it swings toward the left, so that if it were to theoretically be viewed from above, it would appear to be revolving counterclockwise. Conversely, if the left eye is covered, the pendulum would appear to be revolving clockwise-from-top, appearing closer as it swings toward the left and farther as it swings toward the right.Explanation
The widely accepted explanation of the apparent depth is that a reduction in retinal illumination (relative to the fellow eye) yields a corresponding delay in signal transmission, imparting instantaneous spatial disparity in moving objects. This seems to occur because visual system latencies are generally shorter (i.e., the visual system responds more quickly) for bright targets as compared to dim targets. This motion with depth is the visual system's solution to a moving target when a difference in retinal illuminance, and hence a difference in signal latencies, exists between the two eyes.The Pulfrich effect has typically been measured under full field conditions with dark targets on a bright background, and yields about a 15 ms delay for a factor of ten difference in average retinal illuminance. These delays increase monotonically with decreased luminance over a wide (> 6 log-units) range of luminance. The effect is also seen with bright targets on a black background and exhibits the same luminance-to-latency relationship.
Use in stereoscopy
The Pulfrich effect has been utilized to enable a type of stereoscopyStereoscopy
Stereoscopy refers to a technique for creating or enhancing the illusion of depth in an image by presenting two offset images separately to the left and right eye of the viewer. Both of these 2-D offset images are then combined in the brain to give the perception of 3-D depth...
, 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. It can, however, be effective as a novelty effect
Novelty effect
The novelty effect, in the context of human performance, is the tendency for performance to initially improve when new technology is instituted, not because of any actual improvement in learning or achievement, but in response to increased interest in the new technology...
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, Jan. 22, 1989 the Super Bowl
Super Bowl
The Super Bowl is the championship game of the National Football League , the highest level of professional American football in the United States, culminating a season that begins in the late summer of the previous calendar year. The Super Bowl uses Roman numerals to identify each game, rather...
XXIII halftime show and a specially produced commercial for Diet Coke
Diet Coke
Diet Coke is a sugar-free soft drink produced and distributed by The Coca-Cola Company. It was first introduced in the United States on August 9, 1982, as the first new brand since 1886 to use the Coca-Cola trademark...
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)
Moonlighting (TV series)
Moonlighting is an American television series that aired on ABC from March 3, 1985, to May 14, 1989. The network aired a total of 66 episodes...
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 refrigerator
Refrigeration
Refrigeration is a process in which work is done to move heat from one location to another. This work is traditionally done by mechanical work, but can also be done by magnetism, laser or other means...
s 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.
Examples
The effect was also used well throughout the whole 1993 Doctor WhoDoctor Who
Doctor Who is a British science fiction television programme produced by the BBC. The programme depicts the adventures of a time-travelling humanoid alien known as the Doctor who explores the universe in a sentient time machine called the TARDIS that flies through time and space, whose exterior...
charity special Dimensions in Time
Dimensions in Time
Dimensions in Time is a charity special crossover between the British science fiction television series Doctor Who and the soap opera EastEnders that ran in two parts on 26 and 27 November 1993. It was filmed on the EastEnders Albert Square set, and features several of the stars of that programme...
and in dream sequences of the 1997 3rd Rock from the Sun
3rd Rock from the Sun
3rd Rock from the Sun is an American sitcom that aired from 1996 to 2001 on NBC. The show is about four extraterrestrials who are on an expedition to Earth, which they consider to be a very insignificant planet...
two-part season 2 finale Nightmare on Dick Street. In many countries in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, a series of short 3D films, produced in the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
, were shown on television. Glasses were sold at a chain of petrol stations. These short films were mainly travelogue
Travel literature
Travel literature is travel writing of literary value. Travel literature typically records the experiences of an author touring a place for the pleasure of travel. An individual work is sometimes called a travelogue or itinerary. Travel literature may be cross-cultural or transnational in focus, or...
s of Dutch localities. A Power Rangers: Lightspeed Rescue
Power Rangers: Lightspeed Rescue
Power Rangers Lightspeed Rescue is the 2000 incarnation of the Power Rangers TV franchise, based on the Super Sentai series Kyuukyuu Sentai GoGoFive....
movie called Power Rangers in 3D: Triple Force (later broadcast as two-part Trakeena's Revenge) sold on VHS through McDonalds purportedly used "Circlescan 4D" technology, which is based on the Pulfrich effect, but there was very little 3D present. In the United States and Canada, six million 3D Pulfrich glasses were distributed to viewers for an episode of Discovery Channel
Discovery Channel
Discovery Channel is an American satellite and cable specialty channel , founded by John Hendricks and distributed by Discovery Communications. It is a publicly traded company run by CEO David Zaslav...
's Shark Week
Shark Week
The Discovery Channel's Shark Week, which first aired on July 27, 1987, is a week-long series of feature television programs dedicated to sharks. Shark Week is held annually, normally running in July or August. Shark Week was developed to help the average person have a greater respect for sharks....
in 2000. Animated programs that employed the Pulfrich effect in specific segments of its programs include Yo Yogi, The Bots Master
The Bots Master
The Bots Master was a 1993 cartoon series, produced by Jean Chalopin through his company "Creativite et Developpement" in France . In total 40 episodes were made, each one having a special 3D segment and titles. The series was co-produced by Avi Arad and Associates...
, and Space Strikers
Space Strikers
Space Strikers was an animated television series that was based on the Jules Verne novel Twenty Thousand Leagues Under the Sea. The series aired on UPN from 1995 to 1996. Action sequences were shown in "Strikervision" 3-D. It was the first animated series to be made specifically for UPN.-Voice...
; they typically achieved the effect through the use of constantly-moving background and foreground layers.
The videogame Orb-3D
Orb-3D
Orb-3D is an action/puzzle game for the 8-bit Nintendo Entertainment System.-Story:You are an Explorer First Class, on assignment in a remote corner of the universe. Space stations, Colonial Cruisers and whole solar systems have mysteriously disappeared in this region. A nearby planet is buzzing...
for the Nintendo Entertainment System
Nintendo Entertainment System
The Nintendo Entertainment System is an 8-bit video game console that was released by Nintendo in North America during 1985, in Europe during 1986 and Australia in 1987...
used the effect (by having the player's ship always moving) and came packed with a pair of glasses. So did Jim Power: The Lost Dimension in 3-D
Jim Power: The Lost Dimension in 3-D
Jim Power: The Lost Dimension in 3-D is a platform game designed by French developer Loriciel and published by Electro Brain for the Super Nintendo Entertainment System and PC MS-DOS in 1993. The game features several contrasting modes of gameplay, including side-view platforming, top-view, and...
for the Super Nintendo
Super Nintendo Entertainment System
The Super Nintendo Entertainment System is a 16-bit video game console that was released by Nintendo in North America, Europe, Australasia , and South America between 1990 and 1993. In Japan and Southeast Asia, the system is called the , or SFC for short...
, using constantly-scrolling backgrounds to cause the effect.
External links
- EP0325019 - patent using the Pulfrich effect