Abney Effect: What It Is And How It Influences Our Perception Of Color
Our perception deceives us. Many times what we think we see is not what it seems, and One of the examples of this is the curious case of the Abney effect
Discovered at the beginning of the last century, this effect occurs when, when white light is applied to the same color, it is perceived with a different tone, as if the hue or saturation had changed.
Below we will go into more detail about the Abney effect, who discovered it and the physiological explanation behind such a curious phenomenon.
The Abney effect is the perceived change in hue that occurs when white light is added to a monochromatic light source That is, it consists of seeing a color from another tone of color, with specific hue and saturation, when more lighting is applied to it. Adding white light produces, on a psychological level, a desaturation of the monochromatic source, giving the sensation that the color has changed in hue and saturation, even though the only thing that has happened is that it now has a greater luminance.
The nature of this phenomenon is purely physiological, not physical. That the human eye perceives a tone of another color when light is added is something counterintuitive, since the logical thing would be to see that same color only brighter. For example, the color brown is actually nothing more than a dull orange-red that, when white light is applied to it, turns into that color. It feels like we’ve gotten a new color, or that brown has turned into orange, when in reality it has always been orange.
This phenomenon It was first described in 1909 by the English chemist and physicist Sir William de Wiveleslie Abney He discovered that by applying a white light source made from the three primary colors of light, that is, red, blue and green, changes could be induced in the perception of certain colors, even though they essentially remained the same tones.
Chromaticity diagrams
To understand this phenomenon more thoroughly, it is necessary to talk a little about a tool used in color theory. Chromaticity diagrams are two-dimensional diagrams in which colors are represented in XYZ coordinates. The X, Y and Z values, or tristimulus values, are simply used as values to create new colors from primary colors in the same way that the RGB model is used.
In this type of diagrams, two aspects of colors are represented: hue and saturation The hue is the color itself or chromaticity, represented by how close the color is to pure green, red or blue when we talk about light colors. Saturation corresponds to the degree of intensity of the color, going from lighter to more intense. What is not represented in these diagrams is the illumination or luminance of the color.
Colors in chromaticity diagrams are represented in rows and columns. For example, rows can represent hue (blue, blue-green, turquoise, green…) while columns can represent saturation, from lighter tones to more saturated tones. The Abney effect occurs when, when white light is applied to these colors, changes are perceived as if their shades or saturations had changed.
Returning to the previous case, brown and reddish orange are the same color, with the same degree of hue and the same saturation, but they have different degrees of illumination. In a chromaticity diagram both colors would be the same, reddish orange. It would be when the lighting was changed, whether of greater or lesser intensity, that the perceived color would look different, with brown being the result of a reddish orange with low lighting.
This is why chromaticity diagrams are so useful for detecting colors that, by changing only the lighting, we perceive them as new colors on a psychological level. It is through these instruments and simply by shining white light on them that we can detect which colors our brain interprets as if they were different tones.
Physiology of the phenomenon
According to the opponent process model of the visual system, Three neurological channels are involved in color perception: two chromatic channels and one achromatic channel The chromatic channels consist of a channel that perceives red and green (red-green channel) and a channel that perceives blue and yellow (yellow-blue channel), these being responsible for perceiving the tones themselves. The achromatic channel is responsible for luminance, seeing how close the color is to white or black.
Hue, saturation and illumination are perceived thanks to the joint and varied activity of these three neurological channels, which consist of axonal pathways from retinal ganglion cells. The activity of these three channels is closely linked to the reaction time in the response to colors. Some activities depend on one or the other channel, or both types are also involved. The achromatic channel has a faster response speed than the chromatic channels, under most conditions.
There is a specific situation in which the achromatic channel emits a slower response than the chromatic channels, and this is when white light is added to a color that was already being observed. The achromatic channel shows a slightly shorter response time than it would in conditions without bright light. However, its response magnitude will be stronger than the chromatic, giving false perception.
It is not very well known why we can see the same color as if it were another depending on the luminance The spectral sensitivity of the observer, the relative number of each type of cones or the age of the individual do not seem to be factors that influence how intense the perception of different nuances is. What is clear is that the light of the environment in which one is located has a significant influence, making the same image appear a different color, as has been seen in illusions such as that of the blue or white dress.
This would explain why color judgments vary depending on differences in the color environment or exposure to a given color. It could also be due to the amount of time that the retinal cones have been stimulated, causing them, for a short period of time, to not emit an adequate signal when different types of wavelengths affect them.
