The color of the lamps. Which light is better for the eyes: yellow or white? Choosing lamps

Blacker than black

Figure 1 - Model of a completely black body.

Light entering through the hole will be completely absorbed after repeated reflections, and the outside of the hole will appear completely black. Even if we paint the cube black, the hole will be blacker than the black cube. This hole will be completely black body. In the literal sense of the word, the hole is not a body, but only clearly demonstrates we have a completely black body.
All objects exhibit thermal radiation (as long as their temperature is above absolute zero, that is -273.15 degrees Celsius), but no object is a perfect thermal emitter. Some objects emit heat better, others worse, and all this depends on various conditions environment. Therefore, a black body model is used. A completely black body is ideal heat emitter. We can even see the color of a completely black body if it is heated, and the color we will see, will depend on what temperature We let's heat it up absolutely black body. We have come close to the concept of color temperature. Look at Figure 2.

Figure 2 - The color of an absolutely black body depending on the heating temperature.

A) There is an absolutely black body, we don’t see it at all. Temperature 0 Kelvin (-273.15 degrees Celsius) - absolute zero, the complete absence of any radiation.
b) Turn on the “super-powerful flame” and begin to heat up our absolutely black body. The body temperature, through heating, increased to 273K.
c) A little more time has passed and we already see a faint red glow of a completely black body. The temperature increased to 800K (527°C).
d) The temperature rose to 1300K (1027°C), the body acquired a bright red color. You can see the same color glow when heating some metals.
e) The body has heated up to 2000K (1727°C), which corresponds to an orange glow. Hot coals in a fire, some metals when heated, and a candle flame have the same color.
f) The temperature is already 2500K (2227°C). The glow at this temperature becomes yellow. Touching such a body with your hands is extremely dangerous!
g) White color - 5500K (5227°C), the same color of the glow of the Sun at noon.
h) Blue glow color - 9000K (8727°C). In reality, it will be impossible to obtain such a temperature by heating with a flame. But such a temperature threshold is quite achievable in thermonuclear reactors, atomic explosions, and the temperature of stars in the universe can reach tens and hundreds of thousands of Kelvin. We can only see the same blue tint of light, for example, in LED lights, celestial bodies or other light sources. The color of the sky in clear weather is approximately the same color. Summarizing all of the above, we can give a clear definition of color temperature. Color temperature is the temperature of a black body at which it emits radiation of the same color tone as the radiation in question. Simply put, 5000K is the color that a black body becomes when heated to 5000K. Color temperature orange color- 2000K, this means that a completely black body must be heated to a temperature of 2000K in order for it to acquire an orange glow.
But the color of the glow of a hot body does not always correspond to its temperature. If the flame of a gas stove in the kitchen is blue-blue, this does not mean that the flame temperature is above 9000K (8727°C). Molten iron in its liquid state has an orange-yellow hue, which actually corresponds to its temperature, which is approximately 2000K (1727°C).

Color and its temperature

Figure 3 - Color temperature of xenon automobile lamps.

Figure 4 - Color temperature of fluorescent lamps.

On Wikipedia I found numerical values ​​for the color temperatures of common light sources:
800 K - the beginning of the visible dark red glow of hot bodies;
1500-2000 K - candle flame light;
2200 K - incandescent lamp 40 W;
2800 K - 100 W incandescent lamp (vacuum lamp);
3000 K - incandescent lamp 200 W, halogen lamp;
3200-3250 K - typical film lamps;
3400 K - the sun is at the horizon;
4200 K - fluorescent lamp (warm white light);
4300-4500 K - morning sun and lunchtime sun;
4500-5000 K - xenon arc lamp, electric arc;
5000 K - sun at noon;
5500-5600 K - photo flash;
5600-7000 K - fluorescent lamp;
6200 K - close to daylight;
6500 K - standard daylight source white light, close to midday sunlight; 6500-7500 K - cloudy;
7500 K - daylight, with a large share of scattered light from a clear blue sky;
7500-8500 K - twilight;
9500 K - blue cloudless sky on the north side before sunrise;
10,000 K - "infinite temperature" light source used in reef aquariums (anemone blue tint);
15,000 K - clear blue sky in winter;
20,000 K - blue sky in polar latitudes.
Color temperature is source characteristics Sveta. Any color we see has a color temperature and it doesn’t matter what color it is: red, crimson, yellow, purple, violet, green, white.
Works in the field of studying the thermal radiation of an absolutely black body belong to the founder quantum physics Max Planck. In 1931, at the VIII session of the International Commission on Illumination (CIE, often written as CIE in the literature), it was proposed color model XYZ. This model is a chromaticity diagram. Model XYZ presented in Figure 5.

Figure 5 - XYZ chromaticity diagram.

The X and Y numeric values ​​define the color coordinates on the chart. The Z coordinate determines the brightness of the color, it is in this case is not involved, since the diagram is presented in two-dimensional form. But the most interesting thing in this figure is the Planck curve, which characterizes the color temperature of the colors on the diagram. Let's take a closer look at it in Figure 6.

Figure 6 - Planck Curve

The Planck curve in this figure is slightly truncated and “slightly” inverted, but this can be ignored. To find out the color temperature of a color, you simply need to extend the perpendicular line to the point of interest (color area). The perpendicular line, in turn, characterizes such a concept as bias- degree of color deviation to green or purple. Those who have worked with RAW converters know such a parameter as Tint - this is the offset. Figure 7 displays the color temperature adjustment panel in RAW converters such as Nikon Capture NX and Adobe CameraRAW.

Figure 7 - Panel for setting color temperature for different converters.

It's time to look at how the color temperature is determined not just of an individual color, but of the entire photograph as a whole. Take, for example, a rural landscape on a clear sunny afternoon. Those who have practical experience in photography know that the color temperature at sunny noon is approximately 5500K. But few people know where this figure came from. 5500K is the color temperature the whole stage, i.e. the entire image under consideration (picture, surrounding space, surface area). Naturally, an image consists of individual colors, and each color has its own color temperature. What happens: blue sky (12000K), foliage of trees in the shade (6000K), grass in a clearing (2000K), various types of vegetation (3200K - 4200K). As a result, the color temperature of the entire image will be equal to the average value of all these areas, i.e. 5500K. Figure 8 clearly demonstrates this.

Figure 8 - Calculation of the color temperature of a scene taken on a sunny day.

The following example is illustrated in Figure 9.

Figure 9 - Calculation of the color temperature of a scene filmed at sunset.

The picture shows a red flower bud that seems to be growing from wheat groats. The picture was taken in the summer at 22:30, when the sun was setting. This image is dominated by large number colors are yellow and orange in color tone, although there is a blue tint in the background with a color temperature of approximately 8500K, there is also an almost pure white color with a temperature of 5500K. I took just the 5 most basic colors in this image, matched them to a chromaticity chart, and calculated the average color temperature of the entire scene. This is, of course, approximately, but true. There are a total of 272816 colors in this image and each color has its own color temperature. If we calculate the average for all colors manually, then in a couple of months we will be able to get a value that is even more accurate than I calculated. Or you can write a program to calculate and get an answer much faster. Let's move on: Figure 10.

Figure 10 - Calculation of color temperature of other lighting sources

The hosts of the show programs decided not to burden us with color temperature calculations and made only two lighting sources: a spotlight emitting white-green bright light and a spotlight that shines with red light, and the whole thing was diluted with smoke... oh, well, yes - and they installed a presenter to the foreground. The smoke is transparent, so it easily transmits the red light of the spotlight and becomes red itself, and the temperature of our red color, according to the diagram, is 900K. The temperature of the second spotlight is 5700K. The average between them is 3300K. The remaining parts of the image can be ignored - they are almost black, and this color does not even fall on the Planck curve on the diagram, because the visible radiation of hot bodies starts at about 800K (red color). Purely theoretically, one can assume and even calculate the temperature for dark colors, but its value will be negligible compared to the same 5700K.
And the last image in Figure 11.

Figure 11 - Calculation of the color temperature of a scene taken in the evening.

The photo was taken on a summer evening after sunset. The color temperature of the sky is located in the region of the blue color tone on the diagram, which, according to the Planck curve, corresponds to a temperature of approximately 17000K. Green coastal vegetation has a color temperature of about 5000K, and sand with algae has a color temperature of about 3200K. The average value of all these temperatures is approximately 8400K.

White balance

Figure 12 - Modes for setting white balance in a photo camera (video camera).

It should be said right away that the white color of objects can be obtained if use source Sveta with color temperature 5500K(this could be sunlight, photo flash, other artificial illuminants) and if the ones in question themselves objects white (reflect all visible light radiation). In other cases, the white color can only be close to white. Look at Figure 13. It shows the same XYZ chromaticity diagram that we recently looked at, and in the center of the diagram there is a white dot marked with a cross.

Figure 13 - White dot.

The marked point has a color temperature of 5500K and, like true white, it is the sum of all the colors of the spectrum. Its coordinates are x = 0.33 and y = 0.33. This point is called equal energy point. White dot. Naturally, if the color temperature of the light source is 2700K, the white point is not even close, what kind of white color can we talk about? There will never be white flowers there! In this case, only highlights can be white. An example of such a case is shown in Figure 14.

Figure 14 – Different color temperatures.

White balance– this is setting the value color temperature for the entire image. At correct installation you will receive colors that match the image you see. If the resulting image is dominated by unnatural blue and cyan color tones, it means that the colors are “not warmed up enough”, the color temperature of the scene is set too low, it needs to be increased. If the entire image is dominated by a red tone, the colors are “overheated”, the temperature is set too high, it is necessary to lower it. An example of this is Figure 15.

Figure 15 – Example of correct and incorrect installation color temperature

The color temperature of the entire scene is calculated as average temperature all colors given image, so in the case of mixed lighting sources or very different colors in color tone, the camera will calculate average temperature, which is not always true.
An example of one such incorrect calculation is shown in Figure 16.

Figure 16 – Inevitable inaccuracy in setting color temperature

The camera cannot perceive sharp differences in brightness individual elements images and their color temperature are the same as human vision. Therefore, to make the image look almost the same as what you saw when you took it, you will have to manually adjust it according to your visual perception.

This article is more intended for those who are not yet familiar with the concept of color temperature and would like to learn more. The article does not contain complex mathematical formulas And precise definitions some physical terms. Thanks to your comments, which you wrote in the comments, I made small amendments to some paragraphs of the article. I apologize for any inaccuracies.

LEDs are widely used as lighting devices. These are convenient, small-sized and economical light sources. But, unlike incandescent lamps, LEDs have different shades of white light. It is called “color temperature” and is designated Tc.

White LED design

This is a silicon crystal with additives, coated with a phosphor. When flowing through it electric current the crystal emits ultraviolet or blue light, which is re-emitted by the phosphor. The final shade of LED lamps is determined by the type of additives and the composition of the phosphor.

Just a note. The lighting of a room depends not only on the color of the LEDs, but also on the lampshade, protective glass and colors of wallpaper on the walls and ceiling.

What is color temperature

When heated, all bodies emit light: first infrared, and then visible. The spectrum of this radiation can be used to determine body temperature. It is measured in Kelvin (K).

Reference. There are two scales for measuring temperatures: Kelvin (°K) and Celsius (°C). 0°K=-273°C.

Conversely, each shade of radiation color corresponds to the temperature of the object. Therefore, shades of white are usually designated in Kelvin, so as not to come up with definitions like “light yellow” or “white with a blue tint”:

• 0°K – absolutely black body, absence of any radiation;
• 800°K (527°C) – dark red color;
• 1300°K (1027°C) – bright red. This is how heated metal glows;
• 2000°K (1727°C) – orange. This is the color of the coals (not the flames) in the fireplace;
• 2700°K – warm white color. This is how incandescent light bulbs glow;
• 4500°K – neutral white. The color of a cloudy day;
• 5000°K – white. This shade has the color of a sunny afternoon;
• 6800°K – cool white. Lighting at sunrise;
• 9000°K – blue. Thermonuclear reaction color.

Color temperature of luminaires

In addition to power, important parameter is the color temperature of LED lamps. The comfort of being in the interior and the perception of brightness depend on it. By modern standards The emission factor of LED lamps is divided into three groups.

warm light

This is a yellowish color (2700-3500°K), lighting before sunset. Conventional incandescent lamps have this glow.

It is used for home, residential premises:

• in the kitchen, warm light will give food a more attractive and appetizing look;
• in the bathroom and living room, such lighting creates a relaxing effect;
• in the bedroom, warm white light allows you to dim the brightness of the lamps and tune in to a sound sleep;

In the interior, yellow and red shades are enhanced, and blue-green ones are also weakened due to the lack of cool colors in the spectrum:

• blue takes on a greenish tint;
• blue "fades";
• dark blue looks black;
• purple takes on a reddish tint.

Therefore, when decorating the interior in blue or light blue color scheme It is better to use neutral or cold light sources.

Neutral or natural light

Neutral light (3500-5000°K) is closest to natural light and does not distort the color of the interior. Such lamps are used in the following places:

• in children's rooms, where they ensure correct perception of colors;
• in the hallway and bathroom in front of the mirror;
• in the kitchen above the work surface;
• in a floor lamp, bedside sconce lamp on the desk.

Cold light

This is the color of a winter day (cold - 5000-6800°K). Used to create a working mood in offices and factories, as well as additional lighting along with sunlight. A cool shade is perceived brighter than other colors.

In residential premises, such lighting is used in auxiliary rooms:

• in the kitchen, to create bright lighting in the work area;
• in the office for a working atmosphere;
• in the bathroom near the sink will help you finally wake up in the morning.

Attention! In living rooms, such lighting is used only if there is large space and in Hi-Tech style.

Interior colors are distorted reverse side from illumination with warm light: blue and green shades are enhanced, but red and yellow are weakened:

• red takes on a purple tint;
• orange turns brown;
• yellow looks yellow-green.

Therefore, it is better not to use such lighting in a room decorated in warm colors.

Lamp color rendering index CRI

The comfort of staying indoors and productivity are affected not only by the brightness of the light, but also by its shade. No less important is the correspondence of the perceived color to the real one. The numerical designation of this parameter is called the index or color rendering coefficient. It is designated Ra or CRI, from the English. color rendering index.

The reference is daylight. Its CRI is 100. Lighting manufacturers do not strive to achieve this quality. Lamps with a coefficient of more than 80 do not tire the eyes, and with Ra more than 90 they are subjectively no different from the reference ones.

Interesting. A 60W incandescent lamp has a temperature of 2680K and a CRI of 80.

When determining Ra, eight reference colors (DIN 6169) are compared using the International Commission on Illumination (CIE) method. In this case, a distortion of the color of the samples under the studied lighting from the color under the reference lighting is noted. Lamps with Tc up to 5000K are compared with a reference lamp giving a black body emission spectrum, and for lamps with more high temperature the standard is daylight.

The average deviation is subtracted from 100. The result is the color rendering index CRI.

Lamp brightness and color temperature

LED lamps allow you to choose lighting of different shades in different rooms. But general rule“warm white in living quarters, cold white in the office” is not always true.

Dutch physicist Ari Kruitoff studied the perception of lighting of varying brightness and shades. As it turned out, eye comfort depended on both factors in the same room.

Based on the results of the experiments, a graph was drawn up, which is called the Kruitoff curve. It shows color temperature (K) horizontally and illuminance (Lx) vertically. The intersection of these values ​​shows the zones of pleasant (in the middle) and uncomfortable lighting.

For example, the cool white color of lamps at 105 Lux illumination is perceived as comfortable, but when the brightness is reduced it seems unpleasant, with a bluish tint.

Such lighting is installed in offices with a standard of 400 Lux, and in living rooms with normal illumination of 75 Lux it is better to use warm white light.

Attention! When increasing the brightness of light in living rooms, you should replace warm-light lamps with neutral ones, otherwise the lighting will have an unpleasant yellow tint.

The varied color temperatures of LED lamps allow you to organize lighting to your liking, based on the interior design and purpose of the room.

Video

LED products today are a huge success among consumers. In just a couple of years, new light sources began to be used almost everywhere. LED lamps are needed for cars, outdoor advertising, home and other areas of human activity.

But today we will not talk about how these light bulbs are used at home, in public spaces, in cars, etc. In this article we will talk about what the color temperature of LED lamps is and how this indicator affects their heating. But to understand such a concept as LED heating, you need to start with the basics.

The essence of light

Light like physical phenomenon, may have various manifestations. In different light, we will see objects and the reality around us in different shades, which will undoubtedly affect our worldview. At the same time, we can perceive objects more clearly or distortedly.
Color temperature and color rendering index are responsible for the correct lighting and how we perceive the surrounding space.

Pay attention! For the optimal selection of any light source (not only LED) for home, street, car and other areas of human activity, it is imperative to take these two parameters into account. Otherwise, you will feel uncomfortable being in a lit room.

Glow LED lamp

The color temperature of LED lamps must meet certain requirements so as not to cause inconvenience. This is the main characteristic of any type of light bulb, especially those that are capable of heating. It is worth noting that LED light sources are capable of very minimal heating. Therefore, even though they can get a little warm, they are actively used in tandem with stretch ceilings.
Color temperature determines the spectral composition of light radiation, which must be objectively perceived by human visual analyzers (eyes). This indicator is measured for LED lamps, as with other light sources, using a colorimeter. And it is measured in inverse microdegrees or mireds.
When choosing LED models the consumer must be familiar with this indicator in order to make the right purchase. There is a corresponding table to determine the optimal color temperature range.

Color temperature table

Pay attention! This indicator is identical to other light bulbs widely used in the world.

When choosing a light source for your home, street or car, you must remember that the light emitted by the light bulb should be as close as possible to the natural level of illumination.

Features of diode light

The light emitting diode is semiconductor device, which produces a glow when electric current passes through it. The light that such a diode is capable of emitting is located in a fairly narrow spectral range. In this case, the color itself will depend on the material from which the LED semiconductor is made.
The formation of white color in such products is achieved in the following ways:

• combining diodes of different glow colors to produce white light. This method allows you to get excellent color quality with the ability to adjust it. But this method is quite expensive, which affects the price of products that are not available to everyone;
• the use of phosphors to coat diodes. It's pretty cheap and profitable way, which allows you to achieve a higher color rendering index. But here, due to the applied phosphor coating, there is a decrease in luminous efficiency.

Lamp structure

An LED light bulb consists of several diodes or, as they are sometimes called, chips. In addition, there is a driver, which is a device that converts AC with a voltage of 220 Volts D.C., necessary for power supply of diodes. Thanks to this structure, these light sources create a directional luminous flux, which is characterized by the directional angle for the generated glow.

What you need to know

When choosing LED light bulbs, you need to know that they have such a parameter as operating color temperature. It reflects the level at which the light source will produce enough glow. Here it is necessary to remember that car headlights or home lamps must have different glow temperature parameters. Otherwise, they will not be able to effectively illuminate the space around them.
When the temperature is within 5000K, the spectral composition of the emitted light will be more balanced. Here it will be almost identical to daytime sunlight. The color rendering index with these parameters will be equal to 100. However, the maximum color temperature is rarely used, since borderline conditions can harm the eyes.

Color temperature

Pay attention! As the color temperature decreases, the glow will become more red and less blue. And the higher the indicator, the more blue and green colors will be in the glow. This is clearly seen in the example of an incandescent lamp, which creates a glow with a reddish tint.

LED lamps in this aspect have the following positive aspects:

• The lamp housings do not get hot. In fact, heating still occurs here, but it is almost imperceptible. Heating when using this kind of lamps is noticeable only in the example LED strip. But here, too, the main heating comes only from the power supply. The product bodies themselves do not heat up;
• create high-quality white light, which is most suitable for our eyes when it comes to artificial lighting.

Car lighting

Such parameters have made it possible to widely use LEDs for illuminating houses, streets and cars. It’s worth dwelling on the latter case in more detail, since the car can have LED tuning of both the headlights and the entire body.
However, there are also disadvantages here. So, despite the fact that such products hardly heat up, and their bodies do not deform due to constant overheating, they do not always effectively reproduce other shades of light.

Difference between LED lamps

LED products differ from each other in their color temperature coefficient. Today, all products, regardless of their purpose (street, home, car) are divided into three main groups according to their luminescence range:

• range within 2700-3500K. Such products emit white warm light, which is very similar to the glow of incandescent lamps. Used for residential premises;
• range within 3500-5000K. This is the so-called neutral range. The glow here is called “normal white”. The light emanating from paws working in this range resembles sunlight in the morning. Suitable for technical areas of the house (bathroom, toilet), offices, educational premises;
• range within 5000-7000K. The glow emitted in this range is called “cool or day white” light. It corresponds to bright daylight. Applicable for street lighting parks, alleys, parking lots, billboards, etc.

Different glow of lamps

If the color temperature does not correspond to 5000K, shades, with the exception of white, will have warm tones (if exceeding given value) or cold (as this value decreases). At the same time, the housings of the light sources do not heat up, which does not in any way affect the service life of these energy-saving light bulbs.
Remember, when choosing such lighting products, you must always give preference to the most suitable color rendering index.

Conclusion

Certainly, artificial lighting It's hard to beat natural light, but led light bulbs Of all the variety of models, we came as close as possible to this. Plus they barely get hot! When deciding to use LED light sources for illumination, you need to be familiar with such an indicator as color temperature. The luminous flux that will have a direct effect on the human visual analyzer depends on this parameter. If you do not take color temperature into account, then your idea will not provide the desired convenience, but will only bring discomfort.

USB lamps as a desktop attribute Choosing a lamp with a battery-powered sensor for an apartment, ready-made options

The color temperature of LED lamps is important characteristic to reduce eye strain. The temperature property of the lamp's light determines how comfortable and familiar the lighting that this lamp provides will be to the eye.

When talking about color temperature, we are not talking about literal temperature, although expressions such as warm light or cool light are used. When they say warm LED lamps, they do not mean the heat transfer of these lamps. We are talking about the subjective perception of light by the human eye.

A simplified definition of the term color temperature is the conditional glow of a conditional “black” body that is heated to a particular temperature. For example, warm light is light whose characteristics coincide with conventional “black body” radiation, which is heated to a temperature in the range from 800 Kelvin to about 3000 Kelvin.

When applied to lamps, the expression “warm light” or “warm lamp” usually means that the lamp produces light whose temperature is 2700 Kelvin. Light of this temperature is produced by an incandescent lamp with a power of approximately 80 watts. For incandescent lamps, color temperature increases as lamp wattage increases. For example, a 40 W incandescent lamp produces light with a temperature of 2200 Kelvin, and a 100 W incandescent lamp produces light with a temperature of 2800 Kelvin.

Subjectively, this is felt as the degree of “yellowness” of the light. A low-power lamp gives a very yellow light, and with increasing power the light becomes “whiter”, its yellow-red tint decreases. In incandescent lamps, the color temperature depends on the power of the lamp; the more powerful the lamp, the more the tungsten filament heats up. And the more the spiral heats up, the “whiter” the light from it becomes. There is even an expression - white-hot.

In LED lamps, the color temperature is set using a phosphor that is applied to the surface of the LEDs. And LEDs themselves produce very “cold” light, with a shift to the blue part of the spectrum.

List of color temperatures for some light sources:

• 800 K - the beginning of the visible dark red glow of hot bodies;
• 1500-2000 K - candle flame light;
• 2000 K - high pressure sodium lamp;
• 2200 K - incandescent lamp 40 W;
• 2680 K - incandescent lamp 60 W;
• 2800 K - 100 W incandescent lamp (vacuum lamp);
• 2800-2854 K - gas-filled incandescent lamps with a tungsten filament;
• 3000 K - 200 W incandescent lamp, halogen lamp, warm white fluorescent lamp;
• 3200-3250 K - typical film lamps;
• 3400 K - the sun is at the horizon;
• 3500 K - white light fluorescent lamp;
• 4000 K - cold white fluorescent lamp;
• 4500-5000 K - xenon arc lamp, electric arc;
• 5500-5600 K - photo flash;
• 5600-7000 K - fluorescent fluorescent lamp;
• 6200 K - close to daylight;
• 6500K is a standard daytime white light source, close to midday sunlight.

Since in LED lamps the light temperature is set using a phosphor (as in fluorescent lamps), there are LED lamps with different temperatures light - 2700 K, 4000 K, 6500 K.

Warm LED lamps

The so-called warm LED lamps are LED lamps with a color temperature of 2700 K. Such lamps are best used in residential areas. The spectrum of their light is close to the light of incandescent lamps and therefore will be more familiar to the eye. Warm led light It is better to use it if both incandescent and LED lamps are used in the room. In this case, it will be more comfortable for the eyes due to the absence of a sharp difference in light between the lamps different types. There will be no sharp transitions between “warm” and “cold” light.

But when choosing LED lamps, you need to keep in mind that for cheap lamps the actual color temperature may be higher, and significantly higher than the declared 2700 K.

LED lamps 4000 K and 6500 K

Personally, I do not recommend using lamps with a color temperature of 4000K or 6500K. The problem is that for LED lamps with a temperature of 4000K and even more so 6500K, the spectrum (temperature) of light does not correspond to the strength of this light. In nature, the temperature of light increases with the strength (intensity) of that light. For example, on a sunny summer day, in the middle of the day, sunlight has a temperature of more than 6000 Kelvin. At the same time, the light intensity is very high, it is bright, even blinding. And in the case of an LED lamp with a temperature of 6500K and a luminosity of 1000 lumens, the luminous flux that this lamp produces does not correspond to this temperature. In nature, the temperature of light, for such luminous flux, will be approximately 2600 - 2700 K (for example, an incandescent lamp).

This discrepancy between temperature and light intensity creates discomfort. It is no coincidence that the expression “dead light” was coined for fluorescent lamps (in which cold phosphor was first used).

Lamps with high (cold) temperatures are suggested as more suitable for workplaces. Supposedly they provide better lighting. Actually this is not true. The quality of workplace lighting primarily depends on the intensity of the light. Therefore, two lamps, each 1000 Lumens, with a temperature of 2700K will give better illumination than one lamp of 1000 Lumens with a temperature of 4000K.

Introduction………………………………………………………………………………… 1. The concept of color temperature…………………………………………………………… ….. 1.1. Table of numerical values ​​of color temperature of common light sources………………………………………………………………………………….. 1.2. XYZ chromaticity diagram………………………………………………….

1.3.Sunlight and Color Rendering Index (CRI - color rendering index)..

2. Methods for measuring color temperature……………………………...... Sources of information……………………………………………………….

Introduction.

According to our psychological sensations, colors are warm and hot, cold and very cold. In fact, all colors are hot, very hot, because each color has its own temperature and it is very high. Any object in the world around us has a temperature above absolute zero, which means it emits thermal radiation. Even ice, which has a negative temperature, is a source of thermal radiation. It's hard to believe, but it's true. In nature, the temperature of -89°C is not the lowest; even lower temperatures can be achieved, however, for now, in laboratory conditions. The lowest temperature that is currently theoretically possible within our universe is the temperature of absolute zero and it is equal to -273.15 ° C. At this temperature, the movement of the molecules of the substance stops and the body completely stops emitting any radiation (thermal, ultraviolet, and even more so visible). Complete darkness, no life, no warmth. Some of you may know that color temperature is measured in Kelvin. Anyone who bought energy-saving light bulbs for their home saw the inscription on the packaging: 2700K or 3500K or 4500K. This is precisely the color temperature of the light emitted by the light bulb. But why is it measured in Kelvin, and what does Kelvin mean? This unit of measurement was proposed in 1848. William Thomson (aka Lord Kelvin) and officially approved in the International System of Units. In physics and sciences directly related to physics, thermodynamic temperature is measured in Kelvin. The beginning of the temperature scale report begins at the 0 Kelvin point, which means - 273.15 degrees Celsius. That is, 0K is absolute zero temperature. You can easily convert temperature from Celsius to Kelvin. To do this, you just need to add the number 273. For example, 0°C is 273K, then 1°C is 274K, by analogy, a human body temperature of 36.6°C is 36.6 + 273.15 = 309.75K. That's how it all works out just like that.

Chapter 1. The concept of color temperature.

Let's try to figure out what color temperature is.

Light sources are bodies heated to high temperatures, the thermal vibrations of whose atoms cause radiation in the form of electromagnetic waves of various lengths. Radiation, depending on the wavelength, has its own color. At low temperatures and, accordingly, at longer waves, radiation with a warm, reddish color of the light flux predominates, and at higher temperatures, with a decrease in wavelength, with a cold, blue-blue color. The unit of wavelength is nanometer (nm), 1nm=1/1,000,000mm. Back in the 17th century, Isaac Newton, using a prism, decomposed the so-called white daylight and obtained a spectrum consisting of seven colors: red, orange, yellow, green, blue, indigo, violet, and as a result of various experiments he proved that any spectral color can be obtained by mixing light fluxes consisting of different ratios of three colors - red, green and blue, which were called the main ones. This is how the three-component theory appeared.

The human eye perceives the color of light thanks to receptors, the so-called cones, which have three varieties, each of which perceives one of the three primary colors - red, green or blue and has its own sensitivity to each of them. The human eye perceives electromagnetic waves in the range from 780 to 380 nanometers. This is the visible part of the spectrum. Consequently, the light receivers of information carriers - cinema and photographic film or the camera matrix must have a sensitivity to color identical to the eye. Sensitized films and matrices of video cameras perceive electromagnetic waves in a slightly wider range, capturing infrared radiation (IR) close to the red zone in the range of 780-900 nm and ultraviolet (UV) radiation close to the violet in the range of 380-300 nanometers. This region of the spectrum, in which geometric optics and photosensitive materials operate, is called the optical range.

In addition to light and dark adaptation, the human eye has so-called color adaptation, thanks to which it correctly perceives colors under different sources, with different ratios of wavelengths of primary colors. The film and matrix do not have such properties; they are balanced to a certain color temperature.

The heated body, depending on the heating temperature, has a different ratio of different wavelengths in its radiation and, accordingly, different colors of the light flux. The standard by which the color of radiation is determined is an absolute black body (ABB), the so-called. Planck emitter. An absolutely black body is a virtual body that absorbs 100% of the light radiation incident on it and is described by the laws of thermal radiation. And color temperature is the temperature of the black body in degrees Kelvin, at which the color of its radiation coincides with the color of the given radiation source. The difference between the temperature scale in degrees Celsius, where the freezing point of water is taken as zero, and the scale in Kelvin degrees is -273.16, because the starting point in the Kelvin scale is the temperature at which any movement of atoms in the body stops and, accordingly, any radiation stops , the so-called absolute zero, corresponding to a temperature in Celsius of -273.16 degrees. That is, 0 degrees Kelvin corresponds to a temperature of -273.16 degrees. Celsius.

The main natural source of light for us is the Sun and various light sources - fire in the form of a fire, matches, torches and lighting devices, ranging from household appliances, technical devices to professional lighting devices created specifically for cinema and television. And in household appliances, and in professional ones, various lamps are used (we will not touch on their principle of operation and design differences) with different energy ratios in their emission spectra of primary colors, which can be expressed by the value of color temperature. All light sources are divided into two main groups. The first, with a color temperature (Tcv.) of 5600 0K, white daylight (DS), in the radiation of which the short-wave, cold part of the optical spectrum predominates, the second - incandescent lamps (LN) with a Tcv. - 32000K and the predominance of the long-wave, warm part in the radiation optical spectrum.

Where does it all begin? Everything starts from scratch, including light radiation. Black color is the absence of light at all. From the point of view of color, black is 0 radiation intensity, 0 saturation, 0 hue (it simply does not exist), it is the complete absence of all colors at all. Why we see an object black is because it almost completely absorbs all the light falling on it. There is such a thing as a completely black body. An absolute black body is an idealized object that absorbs all radiation incident on it and does not reflect anything. Of course, in reality this is unattainable and absolutely black bodies do not exist in nature. Even those objects that seem black to us are not actually completely black. But it is possible to make a model of an almost completely black body. The model is a cube with a hollow structure inside; a small hole is made in the cube through which light rays penetrate into the cube. The design is somewhat similar to a birdhouse. Look at picture (1).

Figure (1). – Model of a completely black body.

Light entering through the hole will be completely absorbed after repeated reflections, and the outside of the hole will appear completely black. Even if we paint the cube black, the hole will be blacker than the black cube. This hole will be a completely black body. In the literal sense of the word, the hole is not a body, but only clearly demonstrates to us an absolutely black body.

All objects exhibit thermal radiation (as long as their temperature is above absolute zero, that is -273.15 degrees Celsius), but no object is a perfect thermal emitter. Some objects emit heat better, others worse, and all this depending on different environmental conditions. Therefore, a black body model is used. A completely black body is an ideal thermal emitter. We can even see the color of a blackbody if we heat it up, and the color we see will depend on the temperature to which we heat the blackbody. We have come close to the concept of color temperature.

Look at picture (2).

Figure (2). – The color of a completely black body depending on the heating temperature.

a) There is an absolutely black body, we don’t see it at all. Temperature 0 Kelvin (-273.15 degrees Celsius) is absolute zero, the complete absence of any radiation.

b) Turn on the “super-powerful flame” and begin to heat up our absolutely black body. The body temperature, through heating, increased to 273K.

c) A little more time has passed and we already see a faint red glow of a completely black body. The temperature increased to 800K (527°C).

d) The temperature rose to 1300K (1027°C), the body acquired a bright red color. You can see the same color glow when heating some metals.

e) The body has heated up to 2000K (1727°C), which corresponds to an orange glow. Hot coals in a fire, some metals when heated, and a candle flame have the same color.

f) The temperature is already 2500K (2227°C). The glow at this temperature becomes yellow. Touching such a body with your hands is extremely dangerous!

g) White color – 5500K (5227°C), the same color of the glow of the Sun at noon.

h) Blue color of the glow – 9000K (8727°C). In reality, it will be impossible to obtain such a temperature by heating with a flame. But such a temperature threshold is quite achievable in thermonuclear reactors, atomic explosions, and the temperature of stars in the universe can reach tens and hundreds of thousands of Kelvin. We can only see the same blue tint of light, for example, from LED lights, celestial bodies or other light sources. The color of the sky in clear weather is approximately the same color. To summarize all of the above, we can give a clear definition of color temperature. Color temperature is the temperature of a completely black body at which it emits radiation of the same color tone as the radiation in question. Simply put, 5000K is the color that a black body acquires when heated to 5000K. The color temperature of orange is 2000K, which means that a completely black body must be heated to a temperature of 2000K for it to acquire an orange glow.

But the color of the glow of a hot body does not always correspond to its temperature. If the flame of a gas stove in the kitchen is blue-blue, this does not mean that the flame temperature is above 9000K (8727°C). Molten iron in its liquid state has an orange-yellow hue, which actually corresponds to its temperature, which is approximately 2000K (1727°C).