Electromagnetic radiation, varying in wavelength from gamma rays to microwaves, constantly bombards us from all directions. Our eyes are only able to detect how much radiation is coming into them and from what direction if that radiation is within the visible spectrum. Located approximately between 380 and 780 nanometers (Nm).
Useful articles:
What is color rendering index? How does it affect lighting?
What is flickering (pulsation) of light flux?
All articles
The spectral power distribution (SPD) of a light source is presented as graphical or tabular data. This is the amount of radiation emitted by a light source at each wavelength in the visible spectrum only. For example, Fig. 2 shows the SPD of an incandescent lamp. SPD provides the basic physical data needed to calculate the color of a light source.
| Figure 2. Spectral distribution of incandescent lamp power |
Achromasia
Impaired color perception, the cause of which is the complete absence of pigments in the cones. The patient sees only black, gray, white shades. Color vision is not available to him.
This is a hereditary form of color blindness that occurs extremely rarely. Possible slight perception with overly saturated, bright colors.
What do we know about color?
From school physics lessons we know that light is a type of electromagnetic radiation with a certain wavelength. This can be direct radiation (light itself) or reflected radiation (light fell on an object, was reflected and we see it).
So, the COLOR that we see when light hits our retina is the FEELING that arises in us due to this process.
The mechanics of the process are as follows:
- light rays, reflected or emitted, enter the eye
- in the eye, the sensory receptors cones and rods are excited, and the signal is transmitted along the optic nerve to the brain
- in the brain the signal is processed and somehow interpreted
Monochromacy
Impaired color perception, which occurs when there is only one pigment in the cones. In this case, the human eye perceives all shades as one light background. It is most often red.
The patient’s brain perceives absolutely all shades of this color, which is inaccessible to an ordinary person.
Three photoreceptors influencing color perception
When people talk about color, they are usually discussing the appearance of an object (red, pink, purple, brown, white) or a light source (eg, warm-white, cool-white). Although the appearance of color appears to be based on the physical characteristics of electromagnetic radiation reaching the human retina, it is actually the result of signal processing performed by the visual system. More specifically, the appearance of color is the result of calculations performed by three separate "color channels". Each channel receives the same radiant energy hitting the retina and processes it slightly differently. As a result of the research, a general model of the visual system was obtained, which provides a basic explanation of color appearance.
For light to stimulate the brain, it must be absorbed by photoreceptors in the retina. There are three types of cone photoreceptors responsible for color vision, each of which is determined largely by the photopigment contained in that photoreceptor. In Fig. Figure 3 shows the spectral sensitivity of the three conical photoreceptors L, M and S. The letters symbolize the peak spectral sensitivity of the photoreceptors to long-wave, medium- and short-wave radiation, respectively.
| Figure 3. Spectral absorption curves of three types of cones |
Dichromasia
A pathological condition in cones, which contain only two pigments. Dichromasia is divided into subspecies.
It is important to identify them in order to explain to a person what type of activity is suitable for him. It is prohibited to drive a vehicle if you do not perceive a red or green tint. Colorblind people are not recommended to work in a business that requires color differences.
Protanopia
Cones contain only the pigments that are responsible for the perception of blue and green colors. The red tint is not fully perceived. With this pathology, it is not recommended to drive a vehicle, since a person will not be able to read the traffic light signal. The color red is not perceived; a person sees all objects with this shade in yellow. Yellow figures are perceived normally.
In rare cases, the patient sees the color red as gray. For example, Dalton, who described the disease, had protanopia.
Deuteranomaly
The glomeruli lack the pigment responsible for the perception of the green tint. Deuteranopia is extremely rare. After receiving the signal, the cones transmit it to the brain.
He perceives the world around him completely differently. The colors mix indefinitely. That's why a red apple looks blue and green grass looks brown.
Tritanopia
The absence of the pigment in cones responsible for the perception of a blue tint. A person does not perceive not only it, but also blue-yellow and violet-red colors. They look the same to the patient. The violet shade, consisting of blue and red spectrum, looks like just red.
It is important that tritanopia is not a contraindication to driving a vehicle. This is due to the fact that the perception of green and red colors remains normal. The downside is that when dusk sets in, the patient loses visual acuity.
Causes
The reasons for different perception of shades are congenital or acquired. With hereditary pathology, both eyes are affected. In the case of acquired color blindness, unilateral progression of the disease is observed. Color perception disorders develop against the background of a pathological condition in the body:
- retinal diseases;
- optic nerve atrophy;
- disturbances in the functionality of the central nervous system;
- jaundice;
- improper use of medications;
- poisoning by chemical components or their compounds;
- due to cataract removal;
- prolonged exposure to ultraviolet rays on the visual apparatus.
There are several types of acquired color transmission disorder from the eyes to the brain:
- Xanthopsia. Surrounding objects become yellow.
- Cyanopsia. The picture is perceived in blue shades.
- Erythropsia. Vision is colored in red shades.
The appearance of acquired disturbances in the sensitivity of color images is temporary. Elimination of the pathological condition occurs after reducing the impact of provoking factors.
Complete loss of color perception by the visual organs is characterized by additional pathological conditions:
- photophobia;
- decreased level of vision;
- central scotoma.
Incomplete blindness to some shades of colors occurs. This color perception is classified according to shades:
- Protanopia. Insensitivity of the eyes to the color red.
- Deuteranopia. The visual organs do not recognize green shades.
- Tritanopia. It is difficult for the visual apparatus to recognize the color blue.
Complex color blindness may occur. For example, only blue or green shades are not perceived.
Common pathological conditions are protanopia and deuteranopia.
Anomalous trichromasia
With normal vision, all three pigments are located in the cones. If any of them is missing, anomalies occur. A visual defect is considered to be a lack of pigmentation, as a result of which the patient distinguishes colors, but cannot perceive them brightly enough. This is a rare type of disease that occurs in a small percentage of colorblind people.
This is how colorblind people see a traffic light:
Cyanopsia
A color perception disorder in which a person cannot see the green and red filter. The patient perceives the world in blue tones.
A distinctive feature of the pathology is the lack of inheritance. It occurs only in the presence of disease or damage to the eyes or brain. It appears when there are disturbances in the lens or its damage. It ceases to perform its function, as a result of which the retina receives many light rays.
Chloropsia
Impaired perception of incoming light rays, as a result of which a person does not see the entire spectrum. The world is perceived in green tones. The disease is not inherited. Occurs when there is a malnutrition of eye tissue, inflammatory diseases of the retina, or acute poisoning.
A characteristic feature of the condition is the deterioration of the patient’s well-being. Gradually, visual acuity decreases. Photophobia appears. A person begins to see fewer shades. At this stage, it is recommended to consult a doctor to avoid complications such as tissue damage.
Erythropsia
Perception of the world in red tones. Blue and green filters are not visible. The perception of the white shade changes greatly, which becomes yellow. Erythropsia does not occur with hereditary color blindness. It begins after surgery on the eyeball, when exposed to bright light on the retina, especially when examining white snow.
If there is no obvious damage to the eye tissue, the condition resolves quickly. No therapeutic measures are carried out. An ophthalmologist may prescribe sunglasses, which will protect the retina. It is recommended to wear them at any time of the year, especially if your eyes are very sensitive to bright light.
Color blindness is a fairly rare disease. Many believe that it disrupts the perception of green and red shades. But that's not true. There are many subtypes of the disease that are important to diagnose early. Some of its manifestations occur only in the presence of damage or disease. This condition is treatable. Timely detection of the disease increases the success of corrective procedures.
Author's rating
Author of the article
Alexandrova O.M.
Articles written
2029
about the author
Was the article helpful?
Rate the material on a five-point scale!
If you have any questions or want to share your opinion or experience, write a comment below.
How many colors can a person distinguish?
A healthy person with normally functioning eyeballs can distinguish only four colors:
- yellow;
- blue;
- green;
- red.
Thanks to the fusion of these colors, different shades are formed. A person can distinguish up to 100 shades. If his profession involves art, this ability increases, reaching up to 150 shades.
There are diseases in which normal color perception is reduced. Most often, the patient cannot distinguish between red and green tones. In this case, the cones of the retinal apparatus are damaged. If the patient has impaired perception of objects at dusk, this means that there are disturbances in the retinal rods. The disease differs in the number of perceived colors:
- trichromasia (three colors out of four);
- dichromasia (perception of two colors);
- monochromy (recognition of only one color).
The light beam entering the eyes has certain wavelengths that a person can distinguish. These indicators are in the range of 370-710 nm. A person does not recognize anything that is higher or lower.
Eye
We perceive light, and as a result color, with our eyes. The eyes are not very accurate instruments for measuring the intensity of light and color, but they were not supposed to be.
When the ancestors of mammals emerged from the water, they had 4-color vision. Then evolution divided into 2 branches, some of the animals began to increase mass, muscles and teeth and became dinosaurs, and some switched to a nocturnal lifestyle. Subsequently, dinosaurs became extinct, and nocturnal creatures returned to a diurnal lifestyle and over time evolved into you and me. During the period when our ancestors were fleeing from huge predators in the darkness of the night, 2 out of 4 color receptors disappeared as unnecessary. Our ancestors saw the world in blue-green colors, but were incredibly good at distinguishing smells and sounds.
Returning to a diurnal lifestyle, future mammals again needed good vision, and thanks to mutations, the genes in the DNA responsible for the perception of green were duplicated, and soon the brain adapted to use this to recognize the color red. This is how we began to perceive red, the color of ripe fruits and young leaves in the equatorial jungle. This turned out to be our evolutionary advantage in matters of obtaining food and had a positive impact on development.
Fun fact: in modern monkeys, the gene responsible for the perception of red is passed on only to females, and not to every female. But if there are several such females in a troop of monkeys, the entire tribe is more successful in obtaining food.
Due to the fact that “red genes” originated from “green genes”, most often color blindness and different perception features are found in these colors.
Color blindness comes in varying degrees and affects 2-8% of men and only 0.4% of women. Some types of color blindness should not be considered a disease, but rather a feature of vision. For example, people who have difficulty distinguishing between red and green colors can distinguish many other colors. In particular, khaki shades that appear the same to people with normal vision. Perhaps in the past, such a feature gave its carriers evolutionary advantages, for example, helping them find food in dry grass and leaves.
Due to the structure of the eye, different people can perceive and distinguish the same colors differently. Which already makes all disputes about shades of color pointless, because no one guarantees that your interlocutor has any random features that allow him to distinguish shades of color, and the rest of humanity will never even be able to take advantage of this special sensitivity of his.
Moreover, if a person does not have a lens at birth or after surgery, his eye begins to perceive ultraviolet radiation. And then there are women - tetrachomats, in whom a genetic mutation led to the formation of the 4th type of cones and their vision is qualitatively better than usual.
Also, the degree and quality of lighting affects the perception of colors. Color-sensitive cones can perceive color well only in good lighting conditions. The darker it is, the worse we distinguish colors. “If the illumination decreases (twilight state), then red, green and blue colors retain their color tone, and the intermediate colors between them change in the direction of approaching the main ones. So, orange becomes redder, yellow approaches orange, blue and violet turn blue; yellow-green and green-blue lose their shades and approach spectral green. If the brightness of the light streams decreases almost to the state of darkness, only three primary colors differ - red, green and blue. In the gathering twilight, the last color to disappear is blue, turning into whitish, and red turns into black. The change in colors as their brightness decreases is called the Bezold-Brücke phenomenon.”
It turns out that even if the same person looks at the same color under different lighting conditions, he will distinguish the color itself (understand that it is orange), but the specific shade will most likely be different.
Plus, color may vary depending on lighting sources. The sun, considered the reference source, shines with much cooler light than incandescent lamps. And halogen lamps give an unnaturally green light. And all objects that fall under such lighting acquire a certain shade, a little warmer or colder. We have a mechanism in our heads that compensates for different lighting conditions, but it only copes well with primary colors, while shades can already change.
Brain
When the cones and rods are excited, they transmit a signal along the optic nerve to the brain. The brain receives these signals and somehow interprets them. Here are some points that affect the interpretation of the signal:
- our color experience, how often and carefully we work with flowers. He allows you to distinguish different shades of color and knows what words are best to describe the color so that the interlocutor understands.
- our physical and psychological state (with depression, all colors seem faded)
- our taste or emotional preferences
When I was studying painting, we in our group quickly noticed that the same still life or landscape, with the same colors, is painted differently by different people. Some in a colder range, some in a warmer range. Each still life in itself was harmonious, all the light and shadow nuances were well analyzed, but they differed in the overall tone. Even artists with a keen sense of color had different color perceptions.
