The way the eyes perceive colors is very complex and depends on the proper functioning of certain nerve cells and structures in the eyeball. We explain it to you.
Vision is one of the most complex senses in the human body. The same part of a network of nerve cells that transform light stimuli into electrical impulses to be processed in the brain. Are you interested in knowing how the eyes perceive colors? Next we will tell you.
The human eye has various structures that participate in the capture and perception of images; something similar to a camera. The lens is responsible for fixing the objective, while the iris regulates the amount of light that enters the eyeball. For its part, the retina acts as the photosensitive layer responsible for absorbing light beams.
In the retina there are two types of cells that act as photoreceptors: rods and cones. The rods help to distinguish between shapes, figures and contrasts, while the cones allow to give sharpness and differentiate between the range of colors of the light spectrum.
What is the color?
Color is the visual perception produced in the human eye as a result of its ability to discriminate between the various wavelengths that are part of the electromagnetic spectrum. In this sense, when an element or body is illuminated it absorbs part of the light beams and reflects the rest.
All the reflected light is captured by the eye and processed by the occipital lobe of the brain, assigning it a specific tone. In fact, studies affirm that the wavelength emitted by an object is responsible for its dullness, this being the main physical component of color.
In this sense, a banana or a lemon produces wavelengths between 570 and 580 nanometers, which are perceived as yellow by the human eye. However, the perception of color depends on the intensity of light rays that fall on a certain element.
The color of an object or body becomes more opaque until it is finally perceived as black in the absence of light. It is important to note that the black tone is the result of the absorption of all the colors and not a specific wavelength.
Why are there objects of different colors?
Color is an inherent factor in an object’s ability to absorb and reflect wavelengths. Human eyes perceive reflected light beams, which are cataloged in the brain, assigning them different colors. The spectrum of light visible to humans is between 380 and 780 nanometers.
So the eyes perceive reddish colors in blood or in an apple as a result of their ability to capture part of the light and emit a wavelength between 615 and 780 nanometers. Similarly, light beams between 425 and 475 nanometers are captured as blue.
Green, red, and blue are the primary colors of the visible spectrum. Therefore, the variation in the amount of these tones allows to produce and perceive the rest of the colors. However, white is the result of the reflection of all wavelengths simultaneously.
How can we differentiate between colors?
Light is one of the most common forms of energy in the environment, with the sun being its main source. It is distributed through particles that allow it to affect objects. The light beams contain all the colors of the rainbow, which are absorbed and reflected according to the characteristics of the receiving element.
The retina is the neurosensory layer of the eye that captures light stimuli projected in space. Cones are the cells responsible for receiving the wavelengths that describe color. Studies have indicated three types of cones that intervene in the capture of the electromagnetic spectrum, according to wavelength: the L, M and S cones.
The eyes perceive colors by stimulation of photoreceptors that initiate an intrinsic molecular cascade in which substances such as opsin and retinol participate. The end result is the transformation of light stimuli into electrical potentials that describe an inverted image.
Once the electrical stimuli are formed, they are integrated into the optic nerve and then pass through the thalamus and reach the optical radiation. Eventually, the stimuli reach the occipital lobe in Brodmann’s areas 17,18 and 19, where the visual perception process ends and the image is corrected.
Trichromatic theory versus opposite process theory
Currently, there are a large number of theories that try to explain the phenomena that give rise to the perception of color. However, the theories of trichromatic and opposite processes are the most accepted and studied in depth.
The trichromatic theory was developed by Thomas Young in 1802 and modified by Herman Von Helmholtz in 1856. It establishes that in the retina there are three types of cones designed to capture a certain range of wavelengths, corresponding to the colors blue, green and Red.
Young and Helmholtz highlighted that the perception of all colors is the result of the participation of these three receptors, which are activated at different intensities. In this way, the human eye perceives the color red when the wavelength strongly stimulates the red receptors and weakly the blue and green receptors.
On the other hand, the theory of opposite processes was described by the physiologist Ewald Hering at the end of the 19th century, who did not agree with the previous theory. According to Hering, human eyes perceive colors based on a system of opposing channels formed by the colors red, yellow, blue and green.
In this way, red is opposed to green, yellow to blue, and white to black. So the eyes perceive the tone of an object based on two colors that are opposed to each other. However, according to the wavelength captured, one of the colors suppresses the other.
The opposite process theory explains why humans can visualize reddish-yellow and yellowish-green tones, but cannot visualize reddish-green or bluish-yellow tones.
Problems with the way the eyes perceive colors
Alterations in the perception of colors are usually the product of congenital or acquired conditions, according to various studies. Most of these alterations are hereditary and are present in more than 8% of the male population.
They are divided, according to their form of presentation, into the following:
People with abnormal or defective trichromatism are characterized by having the three types of cones necessary for the perception of colors, but they have altered functioning. Therefore, these patients require an intensity of the three basic colors different from that of an ordinary person to be able to discriminate one tone from another.
This condition is responsible for confusing the colors of objects or bodies around them. So, on some occasions, it can be misdiagnosed as color blindness.
Monochromatic patients usually have a total lack in the perception of the colors of the environment. This as a result of the presence of only one type of cones in the retina or the total absence of them; something known as achromatopsia. Similarly, people often have blurred vision and difficulty focusing in dimly lit spaces.
Monochromaticism is generally responsible for the perception of all objects in shades of black, white and gray. For what is often called color blindness.
Dichromatism originates when when the patient has a condition in the functioning of only one groups of cones. Therefore, the retina conserves two systems of cones, allowing the person to have a certain perception of color, although different from normal.
Color blindness is the most common form of presentation of dichromatism. This is a hereditary pathology linked to the X chromosome, which is why it is more frequent in men. It has varying degrees of affection.
How to identify alterations in the perception of colors?
Human eyes perceive the environment through a network of nerve cells known as rods and cones. Problems to identify colors in childhood are usually an alarm sign of some alteration in these cells. At times, people may feel that their vision changes the color of objects.
At present, early medical diagnosis greatly favors the long-term prognosis. So it is recommended that you see an ophthalmologist for any visual symptoms. Although there is no cure for an inherited pathology, acquired disorders can be treated, thus avoiding disability.