About the color rendering index of LED lamps. Color rendering index of various lighting lamps

In fact, it shows how accurately the color of the illuminated object will be conveyed when illuminated by the lamp under study and a standard (the Standard is sunlight or an incandescent lamp - colors are not distorted).
Color temperature is actually the color of light that a lamp emits. (example: the color of the emitted light of a sodium lamp and the color of a fluorescent lamp are different. For a sodium lamp it is yellow, for a fluorescent lamp it is most often white)
The color temperature of a lamp is the temperature to which it is necessary to heat an amorphous black body so that the color of the light it emits is approximately the same spectral composition and color as the light of the lamp under study. Unit of measurement – K (degree Kelvin) color of the glow, for example:
If the temperature of the “black body” increases, then the blue component in the spectrum increases, and the red component decreases. An incandescent lamp with warm white light has, for example, a color temperature of 2700 K, and a fluorescent lamp with daylight color has a color temperature of 6000 K
Color of light - Different people perceive the same color differently. Figuratively speaking, the concept of a particular color is just the result of an unwritten agreement between people to call a certain sensation of the optic nerve a specific color, for example, “red”. It is also known that with age the lens turns yellow, which leads to impairments in color identification. That is, we can say that adequate color perception is the result of a psychological process rather than a physical one.

As you can see, science had to tinker a lot to systematize and strictly scientifically determine the characteristics of the various colors of the spectrum! If the color of the surface of an unheated non-radiating object, that is, one of its reflective (and therefore filtering) characteristics, can be described by the wavelength or its inverse - frequency, then we will act differently with heated and radiating bodies.
Let's imagine an absolutely black body, that is, a body that does not reflect any light rays. For a primitive experiment, let it be a tungsten spiral in an electric light bulb. Let's connect this unfortunate light bulb to an electrical circuit through a rheostat (variable resistance), kick everyone out of the bathroom, turn off the lights, apply current and observe the color of the spiral, gradually lowering the resistance of the rheostat. At one point, our absolutely black body will begin to glow with a barely noticeable red color. If you measure his temperature at this moment, it will turn out that it will be approximately equal to 900 degrees Celsius. Since all radiation comes from the speed of movement of atoms, which is zero at zero degrees Kelvin (-273 ° C) (which is what the principle of superconductivity is based on), then in the future we will forget about the Celsius scale and will use the Kelvin scale.
Thus, the beginning of visible radiation from an absolutely black body is observed already at 1200K, and corresponds to the red edge of the spectrum. That is, simply put, the color temperature of red corresponds to a color temperature of 1200K. Continuing to heat our spiral, while measuring the temperature, we will see that at 2000K its color will turn orange, and then, at 3000K - yellow. At 3500K our spiral will burn out, as the melting point of tungsten will be reached. However, if this had not happened, we would see that when the temperature reached 5500K, the color of the radiation would be white, becoming bluish at 6000K, and with further heating up to 18000K, increasingly bluer, which corresponds to the violet end of the spectrum. These numbers are called the “color temperature” of the radiation. Each color has a corresponding color temperature. It is psychologically difficult to get used to the fact that the color temperature of a candle flame (1200K) is ten times lower (colder) than the color temperature of the frosty winter sky (12000K). However, it is true that the color temperature is different from the normal temperature. The color of light is very well described by color temperature.

The color rendering index (or coefficient) (symbol: CRI - color rendering index; R a) shows how accurately or reliably the light source conveys the colors of the illuminated objects compared to sunlight or. The higher this indicator, the more natural or natural the colors of the objects around us look. Of course, this is only true for people without serious visual defects and color perception disorders. They don't have to read this article.

Determination of color rendering index

The color rendering index is a relative value that can take values from 0 to 100 and characterizes the degree to which the color of a body matches its natural color when illuminated by a certain light source. According to the CIE (1995) methodology developed by the International Commission on Illumination, CRI is calculated from the difference in chromaticity resulting from the comparative illumination of eight standard colors between the test sample and a reference illuminant having the same . The smaller the average difference, the higher the CRI value.

Color rendering index value

A comfortable CRI value for a person (and his eyes) ranges from 80 to 100. Lower values indicate that some colors may not look very natural. Thus, the main natural light source for all earthlings and Martians - the Sun - has the best color rendering with R a = 100.

Color rendering index can be so different!

Color rendering index of incandescent lamps

The light of incandescent lamps is not far from the sun. Their color rendering index is the highest among all artificial light sources and is close to 100, which allows for ideal color reproduction. IKEA candles and a burning mattress can help you achieve equally impressive results, but we don't recommend doing this at home. Unless you're visiting.

Color rendering index of halogen lamps

They are no worse than ordinary incandescent lamps in terms of color rendering, so you can safely use them, if, of course, you manage to connect them correctly.

Color rendering index of fluorescent lamps

Most modern fluorescent lamps from well-known manufacturers have fairly high CRI values: from 80 to 90. But in any case, you should pay attention to the characteristics on the packaging - unpleasant surprises may await you (R a< 75) от очень уж бюджетных моделей.

Color rendering index of LED lamps

Although the color rendering index of the best LED lamps can reach values of 80 or higher, just like good fluorescent lamps, it must be taken into account that there are still quite a lot of lamps on the market with poor color rendering, not counting other disadvantages associated with the peculiarities of using LEDs.

Color rendering index of high pressure discharge lamps

Everything is very bad. Mercury and sodium lamps have the lowest CRI, not reaching 40. However, it is worth highlighting metal halide lamps, which also belong to high-pressure gas-discharge lamps, but the technologies used in them made it possible to achieve a color rendering index of 90 and higher.

Color rendering index(color rendering coefficient, CRI) - a parameter characterizing the level of correspondence of the natural color of a body to the visible (apparent) color of this body when illuminated by a given light source. It is currently the only internationally recognized color rendering rating system that provides some guidance to consumers.

The thing is that when lighting objects with different types of lamps, we see that the result may differ. We are talking about color rendering, how an object will look in the light of a particular lamp. In some cases, the colors will look more accurate and natural, while in other cases they will look completely different from sunlight. It turns out that two different types of lamps can have the same color temperature, but transmit colors differently. The emission spectrum of lamps is uneven and their color rendition depends on the energy of the lamps in one or another part of the spectrum. For example, General Electric SP and SPX fluorescent lamps have approximately the same color temperature as incandescent lamps, but the former have much less energy in the red region of the spectrum. This makes red colors appear brighter under incandescent lighting than under fluorescent light sources.

The color rendering characteristics of a lamp describe how natural the objects around us look in the light of this lamp. And for a quantitative measure, the color rendering index is used. This is a relative value from 0 to 100, which characterizes the level of correspondence of the color obtained when illuminated by the tested lamp to the natural color of the body. 100 corresponds to a complete match as in sunlight, i.e. colors from such a light source are transmitted as accurately as possible. Incandescent lamps are close to this. Color rendering index has the designation R a, also known as CRI - color rendering index.

The term appeared around the 1960s and 1970s. CRI was originally developed to compare continuous spectrum light sources that had a color rendering index above 90, since below 90 it is possible to have two light sources with the same color rendering index but with very different color rendering.

How color rendering coefficient is measured:

To determine it, 8 or 14 test colors specified in DIN 6169 are used (six additional colors are sometimes used for special needs, but they are not used to calculate the color rendering index), which are illuminated by the test lamp and then by a reference lamp having the same color temperature. The smaller the differences in color rendering between the test colors, the better the color rendering of the lamp under test. Which, depending on the index value, characterizes the lamp as having low, sufficient, good or very good color rendering.

The smaller the deviation of visible color from natural color (the higher the color rendering index), the better the color rendering characteristics of this light source.

A light source with a color rendering index of R a = 100 emits light that optimally displays all colors. The lower the R a values, the worse the colors of the illuminated object are reproduced:

There is a system that mathematically compares the change in location on the spectral scale of colors compared to the same colors illuminated by a reference light source. The average differences are then subtracted from one hundred to produce the color rendering index.

Tested colors (primary):

Comfortable for the human eye CRI value from 80-100 R a . LED lamps are good in this regard.

By definition, if there is no difference in how the colors of objects appear, the light source is assigned a CRI of 100. Thus, small differences will result in a CRI closer to 100, while larger differences will result in a lower CRI value. When comparing color temperatures in the range from 2000 K to 5000 K, the reference light source is the blackbody emitter, and with color temperatures above this range, daylight.

It is noteworthy that the color rendering index of both incandescent lamps and the northern hemisphere sky is considered equal to 100, despite the fact that neither of them is truly flawless (incandescent lamps are very weak in illuminating blue tones, and the northern sky at 7500 K, in turn , weak in red tones).

Sunlight: R a 100
Fluorescent lamps with 5-band phosphor: R a 90
Metal halide lamps: R a 70 - 90
Standard fluorescent lamps: R a< 75
Sodium discharge lamps: R a 22

Differences in CRI values less than five units are insignificant. This means that light sources with color rendering indices of, say, 80 and 84 are essentially the same.

Technically, color rendering index can only be compared between light sources that have the same color temperature. However, as a general rule, light sources with high color rendering indices (80-100) tend to make people and things look better than light sources with lower CRIs.

Practical tips:

In furniture showrooms, it is best to use warm light. To maintain a calm and pleasant atmosphere, lamps with a color temperature of 2500 - 3500 K and a color rendering index R a of 85 are ideal.

Paints, curtains, fabrics and wallpaper require clear visibility. Here you should choose a light source with a color rendering index R a 90-100 and a color temperature of 5000 K and above.

Wooden furniture + warm light = great combination. The best choice of light source: color rendering index is R a 80-85, color temperature is 2500-3500 K.

For lighting leather products (chairs, chairs, shoes, etc.), warm light with good color rendering (R a 80-90 and 2500-3500 K) is better suited.

According to the applicability of light sources:

The color rendering index is also required to classify light sources, so that later you can understand which lamps are suitable for a particular use.

Theoretically, the maximum value of this indicator is 100. The lower the color rendering index of a particular lamp, the worse it conveys color shades.

In practice, color rendering indices are divided into several levels. DIN 5035 distinguishes six levels.

Level lamps A1 used in lighting systems where color accuracy is one of the most important requirements - in printing, museums, clothing stores.

To lamps with color rendering level 1B include 3-component fluorescent lamps, which are installed mainly in administrative buildings, schools, sports and industrial facilities.

Level lamps 2A have fairly good color rendering characteristics.

Level lamps 3 apply in heavy industry where color accuracy is not important.

Lamps with color rendering level 4 , with the exception of in special cases of high pressure sodium lamps(Ra=20), should not be used indoors. Such requirements for the characteristics and color rendering levels of lamps for rooms of various types and purposes are provided for by the DIN EN 12464-1 standard.

Have you noticed how much different, for example, photographs taken outdoors under natural light and indoors under artificial lighting differ? Why are the differences so visible? This is due to such a parameter as the lamp color rendering index.

What is it? This parameter allows you to characterize how the color level of an object under a certain lighting corresponds to its actual color level. A similar definition has been accepted internationally.

As you understand, under different types of lighting the perception of the color of an object may be different. Remember how often an ordinary person with a healthy skin color looks pale or yellowish when standing in a room with artificial lighting. Moreover, even lamps with the same luminous flux, but of different types, can convey color differently. This is due to the fact that the light spectrum is characterized by some unevenness, and color is transmitted differently depending on the energy of the light bulb in a particular color spectrum.

We figured out what color rendition is. And its index is used to quantify the perception of colors. It can be in the range of 0-100, and this number shows how close the colors of an object are to natural ones under a particular type of lighting. Of course, the ideal value is 100; such light is almost completely identical to sunlight in terms of color rendering. This index is denoted by the abbreviation CRI, which stands for color rendering index.

The method for calculating this index was proposed in the 70s of the last century. It involved calculating color shifts from so-called reference values. As a rule, 8 colors of the color spectrum are taken for calculation, among which there are shades of dirty pink, light brown, olive and more saturated light green, turquoise, soft blue, light violet and purple. And the more our color source matches the reference colors in color rendering, the higher its color rendering index. The lower the index value, the correspondingly worse the color rendition.

Color rendering index of incandescent lamps

But it is no coincidence that most people prefer everyone else. And this is despite the fact that these lamps quickly fail, are uneconomical and have many superior, more modern analogues. But nevertheless, these lamps are certainly ahead in one parameter - the color rendering index, which is as close as possible to 100 and is more than 90. They are also characterized by a very good degree of color rendering (1A is the maximum value).

Color rendering index of fluorescent lamps

These lamps are also distinguished by a fairly high index value, but it varies greatly depending on the design. Simply put, the simpler the design, the worse the index. The highest value is characterized by lamps with a phosphor of five components; it is not inferior to this value for incandescent lamps (that is, it ranges from 90 and above). If there are three lamp components, then the index is slightly lower and ranges from 80 to 90, while the degree of color transmission also drops to a value of 1B. For even simpler models, the index value can be even lower and range from sixty to 79. So, as you can see, when choosing, it is very important to pay attention to the index parameter, otherwise the quality of color rendition may greatly disappoint you.

Color rendering index of halogen lamps

Another excellent option in terms of color rendering is . The value of their color rendering index is also quite high and, as a rule, is 90 or more. But do not forget that using these lamps will require you to connect a step-down transformer, which somewhat complicates the installation process. But in terms of color rendering, these lamps are a very good choice.

Color rendering index of LED lamps

With color rendering, not everything is so simple. This indicator has a lot to do with the fact who the manufacturer of your light bulb is. It should be noted that fluctuations in the index value depending on the manufacturer can be quite significant and can range from sixty to 89. The color rendering class can also be different for different LED lamps. But in general, these lamps are also considered a very good option in terms of color rendering and you can safely choose them for your home.

But we do not advise you to buy the so-called ones. Their color rendering index is very low and does not exceed forty, which means that such lamps should not be used in residential areas.
More detailed characteristics of color rendering in relation to the degree and color rendering coefficient can be found in the table.

It should be noted that you should not necessarily strive for a 100% color rendering index. The range of index values comfortable for human vision is from eighty to one hundred. Moreover, the difference in values between 90 and 100 is not very visible to the eye.

Depending on the level of color rendering, different lamps are used in different rooms. This is also worth considering when choosing and purchasing a lamp. There are six main levels of color rendering.
It is very important to use 1A lamps in rooms where color rendering and lighting brightness are especially important. In addition to residential and office premises, this category includes museums, printing houses, as well as fitting rooms in clothing stores.

Lighting level 1B is more often used for domestic purposes, including widely used for lighting schools and preschool educational institutions, gyms and stadiums. Lamps 2a, which have approximately similar characteristics, can also be used for the same purposes.

The third class of lamps is not used so widely, mainly where color rendering and lighting brightness are not very important. These could be industrial premises, where color rendering is not so important.

But class 4 lamps are not very suitable for indoor use; their color rendering leaves much to be desired.

An LED is a device that emits light when electric current passes through it. The spectrum of light that an LED emits is in a fairly narrow range. The color of the illumination changes depending on the semiconductor material.
An incandescent lamp does not have such characteristics: it has either a transparent glass bulb or frosted glass. Luminescent ones provide 5 shades: natural, daylight, white, warm or cold light. In the case of LED lamps, having a high color temperature, they produce white light, which is also called “cold”.

The index, or color rendering coefficient, is a parameter that shows how closely the natural color of a body matches the color of that body visible to the eye when illuminated by a given light source. At the moment, there is only one system for assessing this parameter - CRI (color rendering index), which is used all over the world, and, therefore, provides certain guidelines for the consumer.
To put it more clearly: a pear in the light of one lamp can have one shade, and under another lamp - another, even if the color temperature of these lamps is the same. This happens because the light spectrum has an uneven structure, and color transmission will differ depending on the energy level of the lamp in different parts of the spectrum.
The color rendering index gives an idea of how natural objects look under the light of a lamp. It is measured from 0 to 100, where 100 is ideal for sunlight.
It is designated either “CRI” or “Ra”.
At first, the CRI designation was used for a color rendering index above 90, then this concept was expanded.

Method for measuring color rendering index

If the index (Ra) is 100, the color is identical; if it is less, the color changes when illuminated.
It is determined by testing eight of the 6169 specified test colors. They are first illuminated with a lamp whose index is established, then with a lamp taken as a standard, which has the same color temperature indicators. The smaller the difference, the better the color rendering of the bulb being tested.
To determine this, there is a special system that mathematically compares changes in the spectrum scale under the illumination of two different lamps. The average difference values are subtracted from 100, the remainder is our color rendering index.

What colors are used to calculate the index?

There are eight primary colors:

Lilac
Purple aster
Blue
Turquoise
Light green
Light green
Mustard
Withered rose.

Naturally, minimal differences are not taken into account, since they do not have much significance for the perception of color.
The human eye perceives indices best in the range of 80-100. LED lamps, having basically this meaning, are better suited for lighting than others. Fluorescent lamps with a 5-stripe phosphor have an index of 90, metal halide lamps - in the range of 70-90, conventional fluorescent lamps - less than 70, sodium lamps - about 20.

Common color rendering index values

For simplicity of notation, several levels were adopted:

A1 – accurate color rendering (used in shops, museums, etc.
2A – good color rendering
1B – slightly lower (used in schools, administration buildings, etc.)
3 – poor (used in places where the quality of lighting is not important, for example, in warehouses, in industrial buildings)
4 – do not use indoors.

Features of LED color rendering

LEDs can produce white in two ways:

Mixing green, red and blue LEDs
The blue LED is coated with a phosphor.

It is interesting that in a study of human perception of color, it turned out that white, which is obtained by mixing blue, green and red, is much more pleasing to the eye than the original white color. We are talking about comparing white LEDs and LED clusters. It is also surprising that mixed cluster LEDs received a low color rendering index, but in fact showed themselves to be very high.

What should you consider when choosing an index for LEDs?

What exactly do you want from your lamp, is high color rendering so important in this regard?
If appearance is more important than color, then you should choose based on color temperature. For example, white LEDs with an index of about 20 give a pleasant warm light.
If both factors are important, it is best to choose an LED directly on the area you will be lighting.

Consider the nuances

Small differences are not important, but a large gap is very noticeable. It is believed that in lighting with high indexes everything looks better: both people and objects.
But it also has its own characteristics.
Color rendering can be used to your advantage. For example, in a store that sells textiles and the structure of the fabric and its color are important, it is best to use lamps with a high index. But furniture showrooms will look much more profitable in warm light with an index of about 80 and a temperature of 2000-3000. For leather, it is better to use an index of about 90 and a temperature of about 3000.
The CRI rating system is far from ideal, but, in the absence of another, it allows you to at least somehow determine the quality of a lamp’s light.