Chromostereoscopy

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Potential magnetic field reconstruction from NSO/GSFC synoptic chart magnetogram CR1724(Aad van Ballegooijen and Duncan Mackay)

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From Wikipedia:

“Chromostereopsis is a visual illusion whereby the impression of depth is conveyed in two-dimensional color images, usually of red-blue or red-green colors, but can also be perceived with red-grey or blue-grey images.[1][2] Such illusions have been reported for over a century and have generally been attributed to some form of chromatic aberration.[3][4][5][6][7]

The binocular nature of the chromostereopsis was discovered by Bruecke and arises due to the position of the fovea relative to the optical axis. The fovea is located temporally to the optical axis and as a result, the visual axis passes through the cornea with a nasal horizontal eccentricity, meaning that the average ray bound for the fovea must undergo prismatic deviation and is thus subject to chromatic dispersion. The prismatic deviation is in opposite directions in each eye, resulting in opposite color shifts that lead to a shift in stereoptic depth between red and blue objects.”

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In researching the subtle process of natural chromostereopsis Richard Steenblik realized that the chromatic aberration naturally occurring in the eye could be enhanced through the use of prismatic lenses placed in front of the eyes.   This insight eventually led to the granting of several patents and the establishment of the Chromatek company to market the ChromaDepth system.  ChromaDepth lenses consist of a holographically formed film of equally spaced parallel micro grooves oriented vertically.  The structure of the grooves in the left lens causes light entering it to be dispersed into its component colors starting on the right side with red and progressing through the spectrum to blue on the left side.  The structure of the grooves in the right lens causes light entering it to be dispersed into its component colors starting on the left side with red and progressing through the spectrum to blue.  The red end of the spectrum is thus presented to the retina on the nasal side of each eye.  This opposing horizontal displacement of the filtered image falling onto the retina of each eye creates a stereoscopic perception where the red components of an image appear closer to the viewer and blue components further away –with the positioning of the full continuum of the spectrum falling in between those two extremes.
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The ChromaDepth system was soon recognized for its potential.  The following links provide some sense of the range of applications being researched.

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Professor Erwin Verwichte has a very clear description of the effects of color contrast on his Principles of Chromo-stereoscopy page at the University of Warwick:

“In order for the depth to become clear, the colour needs to contrast with a background colour. For the RGB (Red-Green-Blue) colour scale, the background colour is black. For the CMY (Cyan-Magenta-Yellow) colour scale, the background colour is white. The CMY colours are simply the complement colours to RGB in the colour cube. The middleground colour is the complemtary colour of the background colour and appears at the average depth of the image. For the RGB colourtable black is background and white is middleground. For the CMY colourtable the roles are reversed.”

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1. Red-Green-Blue colours on a black background

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2. Cyan-Magenta-Yellow colours on a white background

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The Crayola company produced a version of their high quality sidewalk chalk that was bundled with a set of ChromaDepth glasses.  The special effects simulations in the following 30 second spot commercial give great sense of the fun young artists could have.  Soft chalk.  Hard sell.

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Drawing on pavement with colored chalk makes for a fun class introduction into experimenting with chromostereoscopic principles.

Click this line to access photos of the CalArts 2014 class chromostereoscopic chalk drawing day

Click this line to access photos of the CalArts 2015 class chromostereoscopic chalk drawing day

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The versatile artist, actor, and writer, Leigh McCloskey created a painting in his Malibu studio that he found could not be contained to the canvas on his easel, but lead him into extending the painting onto nearly every available surface in his studio.  When he began that work he was unaware that the color choices he was making made the painting a perfect choice for viewing with the Chromadepth system.  Visitors to his studio are given a pair of Chromadepth glasses to peer into the depths of his painting and a tour of the complex mythological narratives embodied in the work.  Following are two interviews that provide some insights into The Hieroglyph of the Human Soul.

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It is not necessary to present full spectrum saturated color in order to create the sense of three dimensional space in an image viewed with ChromaDepth glasses.  The spectral absorption of water filters out the longer wavelengths of light on the red end of the spectrum causing a fade to the shorter wavelengths on the blue end of the spectrum which is ideal for creating a sense of 3D with the  ChromaDepth system.  The following photograph of Jason deCaires Taylor‘s underwater sculpture, Vicissitudes,  provides an excellent example of this often neglected aspect of enhanced chromostereopsis.

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