Chromostereopsis
It is commonly found in stained-glass, historically artists have been aware of this effect, using it to generate advancing or receding perspectives within the images.
For example, in 1958 Dutch art historian De Wilde noted that in analyzing cubist painter Leo Gestel's painting "The Poet Rensburg", instead of using conventional graded depth cues, "If you put violet next to yellow or green next to orange, the violet and the green retreat.
[12] In this sense, the chromostereoptic effect gives shapes plasticity and allows for depth perception through color manipulation.
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 eccentric foveal receptive system, along with the Stiles–Crawford effect, work in opposite directions of one another and roughly cancel out, offering another explanation to why subjects may show color stereoscopy "against the rule" (a reversal of the expected results).
This multifactorial component of chromostereopsis offers one explanation of the reversal of the effect in different people given the same visual cues.
[12] Other research has also suggested that border contrast changes could lead to color depth reversal with the switch from black to white backgrounds.
They observed that the usual "intensity multiplied by aperture" rule did not apply in foveal vision and that rays entering the eye via peripheral regions of the pupil were less efficient by roughly a factor of five.
[12] Research has attempted to extend the basis for the traditional chromostereoptic theory, including work done by Stiles and Crawford.
[1] Chromatic aberrations are defined as types of optical distortions that occur as a consequence of refracting properties of the eye.
This phenomenon is called chromatic dispersion and has important implications for the optical performance of the eye, including the stereoptic effect.
Unlike LCA, TCA depends on object location in the visual field and pupil position within the eye.
By Snell's Law of Refraction, this incidence angle subsequently determines the amount of chromatic dispersion and thus location of the retinal images for different wavelengths of light.
[14] In TCA, different wavelengths of light are displaced in non-corresponding retinal positions of each eye during binocular viewing.
Color-induced depth effects due to TCA can only be perceived in images containing achromatic information and a single non-achromatic color.
[2] The amplitude of the perceived depth in an image due to the stereoptic effect can be predicted from the amount of induced TCA.
Additionally, pupil displacement from the visual axis is critical for determining the magnitude of the aberration under natural viewing conditions.
Natural selection may have developed these color and texture schemas because it produces the illusion of protruding or receding eyes of much larger organisms than the actual butterfly, keeping potential predators at bay.
[15] Many different methods of testing have been employed to view the effects of chromostereopsis on depth perception in humans.
Technological progress has allowed for accurate, efficient, and more conclusive testing, in relation to the past, where individuals would merely observe the occurrence.
In one method, twenty-five control subjects were tested using color-based depth effects through the use of five different colored pairs of squares.
To enhance this effect, subjects put on blazed grating High Definition ChromaDepth® C3D™ 3D-lenses glasses, which contain a prism structure to refract the light to an angle of approximately 1° and were tested again.
Agreement was good with expected results, supplying additional evidence that chromostereopsis depends on chromatic dispersion.
[16] A neurophysiological study by Cauquil et al. describes V1 and V2 color-preferring cells as coding local image characteristics (such as binocular disparity) and surface properties of a 3D scene, respectively.
The study conducted by Cauquil et al. indicates, based on electrode stimulation results, that both dorsal and ventral pathways in the brain are involved in chromostereoptic processing.
This study also concluded that chromostereopsis starts in the early stages of visual cortical processing, first in the occipito-parietal region of the brain, followed by a second step in the right parietal area and temporal lobes.
Additionally, activity was found to be greater in the right hemisphere, which is dominant for 3D cortical processing, indicating that chromostereopsis is a task-dependent, top-down effect.
