The Effect of Lighting Color on Children’s Vision and Emotion

1. Overview

80% of people’s access to external information comes from the visual system, sometimes called the “window of the soul”. Classrooms, rooms or places where children study, live and play are equipped with artificial lighting sources. Auxiliary lighting is used during the day to supplement the lack of natural light. Lighting sources must be used at night to create a healthy, happy and emotional light and color environment for children.

Children’s visual system is in the growth stage, and the level of vision is constantly changing. If you cannot fully recognize its characteristics and are affected by adverse factors, it is very easy to damage their vision and even hurt their soul. There are more than 500 million children in the world, but the impact of lighting environment on children’s psychology and physiology is not yet understood by the education department and related personnel. Many parents of children do not understand the basic principles and sometimes use improper methods to endanger the physical and mental health of children.

It is reported that the incidence of myopia among college, middle school and elementary school students in the world has reached more than 53%, among which 21% are elementary school students, 48% are junior high school students, 71% are high school students, and 73% are college students. This is an issue worthy of attention. It is very complicated to investigate the reasons. In addition to the genetic factors of each person, it may be due to high learning pressure, long time reading and reading, not paying attention to reasonable rest, poor lighting or lighting design in the classroom, and unreasonable and lack of lighting environment for reading at home Knowledge of eye and vision health care, the popularization of information life, TV and computers entering daily life, the beating image of the display screen damages the eyesight of students, etc.

The correct choice of light and color environment can reduce students’ visual fatigue, stimulate learning mood and interest, improve learning efficiency, and benefit children’s IQ development and healthy growth. This article makes a preliminary discussion on the influence of the elements of the light environment on the growth of children, which can arouse the attention of all sectors of society.

2. Illumination

To see objects clearly, there must be enough light to perceive the existence of various objects. In the darkness without light, the visual mechanism loses its function, and people’s inner emotions become confused, fearful, irritable, and painful. If in a good light and color space environment, children feel comfortable psychologically, concentrate their attention, study efficiency is high, the mentality of the lecturer is also relaxed, can see and master the emotions of the students, and the teaching effect is good.

Illuminance is the most basic technical indicator of the visual light environment. It refers to the luminous flux value per unit area of ​​the illuminated object. Its unit is the number of lumens per square meter (lm/m2) or Lux (Lux). To measure. Under high illuminance, it is easy to see objects, distinguish small fonts and images, with high resolution, and human eyes do not feel tired. On the contrary, under low illuminance, there is insufficient light and small fonts cannot be seen, low resolution and easy eye fatigue , Injured, suffering from myopia.

Various lighting engineering facilities must have scientific and reasonable illuminance standard values, and the illuminance distribution must be carried out correctly.  The international standard classroom illuminance stipulated recently is 300 Lux. In fact, the illuminance in the classroom during the day is the combined effect of daylight and lighting. The night classroom must be equipped with complete lighting facilities, and the illuminance on the desk of each class should be greater than the standard value. The illuminance standard of classrooms in some developed countries has been increased to 500 Lux.

During the middle school period, students have heavy learning tasks, reading books and doing homework for a long time, eyes are extremely fatigued, and it is a period of high incidence of myopia. Therefore, the lighting design of middle school students’ classrooms should be paid enough attention. In some areas, the illuminance in the classrooms of primary and secondary schools is seriously insufficient, which is below the minimum standard value of 150 Lux, which harms the physical and mental health of students and reduces learning efficiency. The illuminance of some special classrooms (such as drawing and painting) is increased to 500-1000 Lux to get a clear light environment. However, some newly-built schools are one-sided pursuit of brightness, or the design is unreasonable. The illuminance is as high as 800-1000 Lux, which forms dazzling reflected light on the students’ books and desktops. The students’ eyes are prone to fatigue and waste of electricity.

If there is sunlight shining on the desk of the class, the illuminance is as high as thousands Lux, which will cause students to be unable to see the teacher’s writing on the blackboard and damage their eyesight.  The light radiated by the electric light source of classroom lighting is redistributed by the lamps, so that the illuminance on the desktop of each class reaches the required value. Due to unreasonable design or poor quality of the lamps, the illuminance is distributed unevenly and the difference is large. If the observer’s subjective judgment is already unsatisfactory, it will inevitably affect visual performance and comfort. Illumination uniformity refers to the ratio of the minimum illuminance everywhere to the average illuminance value in the classroom, and it is generally required to be greater than 80%. People reading or working under different illuminances can also cause eye fatigue.

The visual effect of the human eye is composed of a variety of complex factors and varies from person to person. Different years have different requirements for the brightness of the light. The older the age, the light transmission performance of the eye lens becomes worse, and higher illumination is required. Even if the same person has different requirements and responses to lighting due to environmental differences and emotional changes. It is best to use adjustable-brightness lamps for reading lights to get a comfortable lighting environment.

3. glare and flicker

(1) Glare 

Glare refers to the appearance of light that directly stimulates the eyes in the visual field, which reduces visual function or visibility (called disabling glare) or causes visual discomfort (called uncomfortable glare). The light from a high-brightness light source directly enters the field of view is called direct glare, such as sunlight shining on the desktop; the light that enters the field of view after being reflected by a glossy surface is called indirect glare. Uncomfortable glare will appear in the classroom, and disability glare will hardly appear.  The light-emitting area of ​​the lighting source should be as small as possible to prevent direct glare from affecting the vision. As the illuminance into the eyes increases, a light curtain phenomenon appears, making it more difficult to see objects.

Fluorescent tubes are mostly used for classroom lighting and equipped with light-distribution lamps with good reflection. The lamps and the blackboard should be arranged vertically, so that students can see that the light-emitting area in the lamps is reduced.  The viewing direction of the entire classroom is toward the blackboard, and the lighting of the blackboard is also very important. It is required that no glare is generated on the blackboard, and the illuminance is evenly distributed throughout the blackboard so that students can see the blackboard clearly. Teachers should not have direct glare interference during lectures, and there should be no reflected glare on the blackboard into the teacher’s eyes. The lighting of the blackboard adopts angular reflector lamps, and the direction of the lamps is correct. There is enough vertical illuminance to make the average illuminance generated on the blackboard reach about 350 Lux. In order to reduce uncomfortable glare, the lamps are equipped with milky white or prism transparent lampshades. Obviously, the illumination on the desk is uniform and soft, but the illumination is reduced by 25-30%.

2) Flicker

The discharge characteristics of fluorescent lamps must use a ballast to start and stabilize the operating current. Traditionally, an inductive ballast is used. After 50Hz alternating current is applied, it will produce 100 times of light fluctuations per second, the so-called flicker. When the voltage is unstable, the flicker phenomenon is particularly serious. If you learn to read for a long time in a severely flickering lighting environment, your eyes will be fatigued easily, resulting in poor vision. If working with a high frequency current of 20-50KHz, the discharge light is very stable, the light output intensity will not flicker, and the flicker phenomenon will be avoided.

Modern electronic ballasts are used for high-frequency operation. This is the case for writing desks that protect eyes on the market. At the same time, a large number of actual tests have shown that the luminous efficiency of fluorescent lamps working at high frequencies is 10-15% higher than that at low frequencies. . In order to create an energy-efficient, high-quality light environment, electronic ballasts should be fully understood and used. At present, there are electronic ballasts with dimming or automatic dimming, which can meet the needs of various occasions and obtain the illuminance that people need. Can save a lot of energy.

Because architectural lighting designers do not have a deep understanding of the development of lighting technology, and because of market price competition, the market sometimes ignores the reliability and life of electronic ballasts.
In order to reduce expenses, users often avoid using electronic ballasts. Therefore, many people always like to use inductive ballasts with high power consumption, low light efficiency, and flicker.
With the rapid development of information technology, televisions and computers have entered ordinary families, and more and more children are playing game consoles. The flickering image on the terminal display stabs the eyes for a long time, and the X-rays transmitted by the picture tube will be very serious, which will damage the eyes and affect the eyesight.

4. color temperature

When light enters the eyes, you will feel the color of the light source. Different luminous bodies have different light colors. When the color radiated by the light source is the same as the color of the black body thermal radiation, the temperature of the black body is called the color temperature of the light source, and the unit is represented by the absolute temperature scale “K”, which is the characteristic value of the color difference of the electric light source.
The color temperature of the fluorescent lamp is 6500K daylight color (RR), 5000K neutral white (RZ), 4000K cool white (RL), 3500K warm white (RB), 3000K warm white (RN), 2700K incandescent color (RD).

The choice of the color temperature of the light source depends on the ambient temperature, use occasion and light color temperature preference. The light source with high color temperature (≥5000K) is cool and contains more blue light, which makes people feel calm. Mainly used in serious occasions such as production workshops and conference rooms.
The light source with low color temperature (≤3000K) is warm color and contains more red light, giving people a lively, warm and pleasant psychological feeling. They are generally used for lighting in kindergartens, homes and hotels.
The medium color temperature light is between the high color temperature light and the low color temperature light. Red, green, and blue color components are more abundant. It can be used in shopping malls, fast food restaurants and supermarkets.
The higher color temperature makes the eyes tired easily. The light with low color temperature is softer, giving people a comfortable feeling, the light is less irritating to the eyes, the distinguishing ability is slightly lower, and the psychological feeling is more relaxed.

In tropical or subtropical regions, the temperature is relatively high. People like to use high color temperature lights to create a quiet and cool environment. In cold or temperate areas, where the temperature is low, you can use low or medium color temperature lamps to enhance the warm atmosphere. Under normal circumstances, people use high color temperature lamps in summer and low color temperature lamps in winter.

The illuminated objects in the classroom are books and human faces. The white light with high color temperature illuminates the book and makes people feel pure white, but the white light reflected by the paper enters the eyes and easily causes fatigue.
People of different skin tones tend to like light colors of different colors. White people like light sources with low color temperature, such as Europe and North America. Black people like white light, such as Africa, Southeast Asia and South America. Most of the fluorescent lamps used in China are 6500K daylight color, which is the result of long-term habit.
At the same time, people always think that the brightness of high color temperature lamps is higher than that of low color temperature lamps. In fact, the luminous brightness of the low color temperature lamp of the same type of fluorescent lamp is greater than that of the high color temperature lamp. The light with high color temperature stimulates the eyes and makes people feel bright. The light with low color temperature is soft, less irritating to the eyes, and looks dim.

Use soft and comfortable light as much as possible for the children’s learning and playing environment, which is conducive to children’s vision. Do not use strong light, as it will harm children’s eyes. In terms of illuminance, you can choose 200-500Lux for learning and reading, 150-200Lux for game activities, and 75-150Lux for general lighting.

The color temperature of the light should be low to create a soft, lively and joyful atmosphere. Sometimes, the lighting design shines light on the wall or ceiling, and then diffuses the light throughout the space to obtain a soft and diffuse light color environment.
For classrooms of middle school students, it is best to use 4000K mid-color temperature lighting in temperate areas. Because the geographical location is a temperate climate, the skin is pale yellow, and the light is less irritating to the eyes, which is conducive to mobilizing the learning mood and caring for the original habits. It is suitable for high color temperature lamps.

Middle school students are getting older, studying harder and harder, and having more and more homework. The illuminance should be greater than 300 lux. Children should not live in a single light color environment, otherwise it will cause poor color recognition ability. Therefore, the surface and interior decoration around the children’s living space should use colors that children like.
International studies have shown that blue, yellow, yellow-green and orange are conducive to the development of children’s IQ, while white, black, and brown are not conducive to the development of children’s IQ. Of course, it should not be in a colorful, flashing, and jumping light environment, otherwise it will affect the normal development of vision and make children become irritable.

5.Color rendering

The ability of light to faithfully restore the color of colored objects is called color rendering. Sunlight contains light of various colors and can reproduce any color on an object. Artificial light is composed of many different colors of light, and its ability to reproduce the color of an object is also different.
The ability of the light source to restore color is represented by the color rendering index Ra. Usually sunlight is the standard: Ra=100. The Ra values ​​of other light sources are all less than 100. The greater the Ra value, the better the color rendering. Textile factories, color printing factories, clothing stores, handicrafts, historical relics, home decorations, hospitals and clinics, etc., have high requirements for color rendering index, which need to reach at least Ra=80-95.

High color rendering is conducive to children’s visual performance, feels natural and comfortable, and can improve the ability to distinguish colors and learning efficiency. Recently, advanced countries in the world use Ra 80-85 three-color LED straight tube lights for classroom lighting, which can significantly improve the visual light color environment and save lighting power consumption.

When objects of the same color are illuminated by two different light sources, the colors appearing are different, and sometimes some colors will be distorted. For example: under the yellow-white light of a high-pressure sodium lamp with a color temperature of 2000K and Ra=20, blue objects become black. Since there is no blue light in the light, the radiation spectrum of the high-pressure mercury lamp lacks red light components, and the human face appears purple when illuminated by this lamp.
Sometimes color affects physical and psychological changes. For example, a child may cry in a yellow light environment. Sleeping under the light of this color temperature is prone to myopia, because children under 2 years of age are in the stage of visual development. In order to meet people’s emotional needs and different use occasions, the color temperature and color rendering index of the light source should be correctly selected.