The Pulfrich Effect and 3D Glasses

What is the Pulfrich Effect?

The Pulfrich effect, it is lateral motion of something in the field of view being interpreted as being closer or farther away because of the different speeds the two eyes see. This effect can usually be induced by covering one eye with a dark filter. Carl Pulfrich, a German physicist, first described this phenomenon in 1922 and it is named after him.

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 is typically grey) 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.

Apparent depth is a concept often explained as a phenomenon that occurs when retinal illumination decreases in terms of the other eye yields a corresponding delay in signal transmission, imparting instantaneous spatial disparity in moving objects. This would appear to happen because visual system abeyances are usually shorter for (The eyes easily responds faster to) well lighted items compared to poorly lighted items With a deep movement (this was originally described by Carl Pulfrich , who was a German physicist) When there is a discrepancy between retinal illuminance between the eyes which produces an inequality in signal latencies, this is how moving objects are handled by human vision.

Scientifically, the Pulfrich Effect was typically measured under the conditions of a full field consisting of dark targets on a bright background, yielding nearly 15ms. a delay for an amount of 10 difference in the typical retinal illuminant. In a monotonically manner, the delays will increase while the luminance decreases over a wide area. (> six log-units) There is a vast spectrum of light. The effect is also seen with bright targets on a black background and exhibits the same luminance-to-latency relationship.

There are several types of eye disease, like cataracts, that can cause this effect. In these cases, symptoms that have been reported include having a hard time judging the paths of cars that are coming forward.

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. The glasses are used to create a three-dimensional illusion, similar to all kinds of stereoscopy. By placing a neutral filter like the darkened lenses on some sunglasses over one eye, an image, as it moves right to left as well as left to right, excluding up and down seems to move in distance, either away from or closer to the viewer.

The Pulfrich effect hinges upon movement in a specific direction to create the effect of depth, it cannot be utilized as a general stereoscopic technique; for instance, it cannot be utilized to show an unmoving object seeming to extend into or out of the screen; comparably, articles moving in a vertical direction will not be perceived as moving in depth. In contrived visual scenarios, 3D glasses can provide a novelty effect. Material formed with taking advantage of the Pulfrich effect in mind has the added advantage of being completely interchangeable with "normal" viewing, thus eliminating the need for "special" glasses.

The effect became somewhat popular in TV during the 90s. For instance, a 3D TV commercial in the 90's used it by having objects going in one direction seem to be closer to the viewer. (actually in front of the television screen) and they seemed to be further away from the viewer when moved in the opposite direction. (located in the back of the television screen). To allow viewers to see the effect, the advertiser provided a large number of viewers with a pair of filters in a paper frame. There was a dark gray eye filter whereas the other one was more see-through. In this instance, the commericial was restricted to objects only like a skateboarder or a refrigerator moving from left to right across the screen down a sharp slope, a bearing relying on the perception from whichever eye the darker filter covered.

In the Doctor Who of 1993, the Pulfrich effect was well utilized for the charity special Dimensions in Time.

In Europe, there was a series of short 3D films shown on televison that were produced in the Netherlands.

You could purchase the special glasses at gas stations. Basically, these films were short travelogues of different Dutch locations.

An episode of Power Rangers sold through McDonalds used "Circlescan 4D" technology that is based on the Pulfrich effect. Animated programs that used the Pulfrich effect in particular segments of their programs include The Bots Blaster and Space Strikers; they normally accomplished the effect by using the consistently moving backdrop and forefront layers.

The videogame Orb-3D for the Nintendo Entertainment System used the effect through keeping the player's ship continually moving and also included a set of glasses. Jim Power: The Lost Dimension in 3-D also did this within the realm of Super Nintendo games. In this instance, the effect was produced by using continuous-scroll backgrounds.

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.

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