2700k what color? What you need to know about the light temperature of an LED lamp

June 27, 2018

The color temperature of LED lamps is an important characteristic for reducing 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 produces a very yellow light, and as the power increases, the light becomes “whiter” and the yellow-red tint in it 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 light temperatures - 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 that of incandescent lamps and therefore will be more familiar to the eye. It is better to use warm LED light even 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 lamps of 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 a 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.

One of the important characteristics of any artificial light source is color temperature (Tc). In simple terms, this parameter shows what the light shade is - warm and yellowish, neutral white or bluish-cold. The color of LED lamps, unlike lamps of other types, can be in a much wider range of values. That is why in LED-based light bulbs the T c parameter is given special importance.

Unit of measurement

From a physics point of view, color temperature (T c) characterizes the intensity of radiation from a light source in the operating frequency spectrum and functionally depends on the wavelength. It affects the color perception of illuminated objects by the human eye. It is measured in degrees Kelvin (°K).

In some cases, as a more convenient value, the value in mireds (M) is used. Mired, or inverse microdegree, is equal to one million divided by the value of Tc in Kelvin.

The temperature of the light tint of LEDs used in general and additional lighting fixtures is set using a phosphor layer. The method of applying the phosphor, the chemical composition and thickness of its layer are the determining factors for the future color and brightness characteristics of the LED lamp.

SP 52.13330.2011

The color of any physical body is determined by its spectral composition and the nature of the lighting that affects it. This means that when the same object is illuminated with LED lamps with different color temperatures, this object will have different shades. In order to set certain standards, SP 52.13330.2011 “Natural and artificial lighting” was developed.

SP 52.13330.2011 is an updated version of SNiP 23-05-95, valid in Russia until May 20, 2011.

SP 52.13330.2011 establishes standards for all types of lighting used in buildings and structures, in production and in open areas. Regarding the color of light, the document provides for the use of artificial sources, the color temperature of which should not go beyond 2400-6800°K.

In addition to a number of norms and rules, SP 52.13330.2011 provides recommendations for lighting of various types of premises. For example, in residential areas it is recommended to use yellowish-warm light temperatures that create a cozy atmosphere, and in work areas it is recommended to use cooler light temperatures that promote a working atmosphere.

The importance and selection of the correct light shade

It has been scientifically proven that the shade of light affects the psychological impact of space and can significantly change the perception of the appearance of illuminated objects. And it has also been proven that the correct choice of light temperature can have a beneficial effect on human behavior. For example, in a jewelry store, a well-chosen shade of display lighting emphasizes the beauty of the product and promotes sales.
The color temperature of LED lamps directly affects the comfort in the illuminated room. According to the Tc value, all LED lamps are usually divided into 3 groups:

warm glow 2700–3500°K;
neutral glow 3500–5300°K;
cold glow 5300–6800°K.

Warm-colored LED lamps are ideal for home and living room lighting, as their light is less irritating to the eyes. Warm tones give objects a yellowish tint and create an evening atmosphere. It is worth noting that LED lamps with a warm glow are indispensable for organizing lighting in recreation areas.

Neutral light is used in lighting industrial premises and offices. LED lamps with T = 4000-4500°K help improve performance, which has been proven by practical research. A further increase in color temperature with a transition to the cold region leads to sudden fatigue and nervous tension. Within an apartment, LED lamps of neutral light can also be used:

as the main lighting of the bathroom;
in table lamps designed to illuminate students’ workplaces;
in the kitchen where food is prepared.

LED lamps with a T of more than 5300°K can only be installed in non-residential premises and workplaces where high concentration of attention is required for a short time. In addition, they are effectively used in emergency lighting.

In conclusion, it is worth noting once again that the color temperature of LED lamps is an important characteristic, for the selection of which there are many tables. But you definitely shouldn’t choose an LED lamp based only on the light shade parameter. The correct choice is possible only taking into account all the technical features.

Color temperature in physics

In the works of Max Planck, the founder of quantum physics, more than once
the laws of energy distribution were described. Part of the Nobel Prize laureate's research concerned the study of absolutely black bodies, which made it possible to identify such a concept as color temperature. The unit of measurement for this quantity is Kelvin, as in the case of absolute temperature. According to the formula, this indicator is equal to the temperature of the black body at which the body emits radiation in the same color range as that being measured.

The sequence of observations is as follows:

The lighting is turned off, current is supplied to the terminals.
The resistance gradually decreases.
The black body begins to barely noticeably illuminate in red.

When measuring the temperature of an object at this moment, the indicator will most likely reach 900 ºС. The principle of superconductivity indicates that at zero Kelvin, the speed of atoms is also zero, but the radiation itself depends on it. For convenience, it is better to discard the Celsius scale accepted in our latitudes and use a foreign one.

Color temperature and its tint display

The beginning of the visible spectrum of the blackbody radiation is characterized by an indicator of 1200 K. It is this mark that is the boundary of the red tint. If you continue the process of heating the coil, you will notice significant color changes. Already at 2000 K, red will be replaced by bright orange, which will gradually turn into yellow, and will be completely replaced by it when it reaches 3000 K. The color temperature of the lamps can correspond to a warm or cold range.

For tungsten filaments, the peak is around 3500K, after which they begin to melt, but light sources based on a different operating principle can easily heat up further.

The color temperature of LED lamps can easily reach 5500 K or more. With this indicator, you can see the usual bright white color. With subsequent heating to 6000 K, the radiation will become somewhat bluish, deeper and deeper into this shade, until, upon reaching 18000 K, it comes close to the violet edge of the spectrum.

Color temperature and lighting

When designing a lighting system, it is important to take into account many nuances, but it is the color temperature that is responsible for the perception of shades. Cold and warm colors differ significantly in their performance. Thus, the flame temperature of an ordinary candle is characterized by 1200 K, and the winter sky - by 12000 K.

Table 1. Color temperature and shades

Hue	Characteristic
2700 K	Warm white, reddish white	Used in conventional incandescent lamps. Makes the interior more comfortable, truly homely.
3000 K	Warm white, yellow-white	Characteristic of most halogen lamps, slightly cooler than light from an incandescent lamp.
3500 K	Regular white	This is the radiation from fluorescent tubes of various sizes.
4000 K	Cool white	It is an indispensable attribute of the high-tech style, but its “sterility” evokes thoughts of an operating room.
5000-6000 K	Day	Used to simulate sunlight in greenhouses, terrariums, etc.
6500 K	Cold daytime	Used in professional photography and cinematography.

The selection of lighting sources should be carried out depending on the desired effect. The intensity and color temperature of lamps may also be perceived differently depending on the time of day.

LED based lighting

Lighting systems are increasingly based on these elements. The color temperature of LEDs includes 3 main shades:

Warm white (in foreign sources - Warm White (WW)) - up to 3300 K.
Neutral, also known as natural white - Neutral White (NW) - up to 5000 K.
Cold white - Cool White (CW) - over 5000 K.

LED lamps largely determine the area of their use. Street lighting, advertising and automobile lamps have different range and brightness levels.

Differences between the main gradations of white

When selecting a lighting source, it is very important to predict how the illuminated object will be perceived. This is relevant not only when selecting lamps for photo shoots, but also when planning a home interior or developing street lighting systems.

The color temperature of the LEDs will help not only determine the contrast and maximum distance, but also make it possible to understand how the lamp will behave when weather conditions change.

Cool white light sources

Only the sun can boast of ideal perception accuracy; other lighting sources have only more modest indicators. The color temperature of most factory-made LED-based luminaires is in the range from 5000 to 7000 K. The average transmission index is about 65 units.

The advantage of cool white sources is their contrast, which is ideal for illuminating dark objects. Together with the long illumination distance, the color temperature of LED lamps in the cold range makes the lamps the most efficient for the road. Moreover, this shade demonstrates maximum distortion of color perception.

Neutral and warm light sources

Manufacturers of lighting elements do not limit themselves only to cold colors, which are the sharpest and worst perceived by the human eye. The color temperature of LED lamps is 2500-6000 K, which makes it possible to achieve a color rendering index of 75-80 units. Such lamps demonstrate excellent results at relatively short distances.

Lamps with warm and neutral shades show the greatest advantage in unfavorable weather conditions. Rain, fog and smoke, which become obvious obstacles for cold lamps, are not so significant for warmer lamps. The fact is that such sources illuminate not so much the object itself as the space before it. For the same reason, warm light sources are more effective underwater.

Other lighting sources

The color temperature of energy-saving lamps used for home lighting often corresponds to the warm spectrum. Cold springs are quite harsh, and they are unlikely to make your home more comfortable. In general, the characteristics of home lamps are determined, rather, by their brightness and service life. When choosing automotive lighting, other indicators are important.

Xenon color temperature

Xenon and bi-xenon lamps differ not only in manufacturer, but also in their features, which largely depend on the color temperature.

Lamp properties:

Bright yellow color (3000K).Mainly used in anti-fog
lighting, has a luminous flux of about 3300 lumens.
Yellow-white (4300 K). Typical of factory fog and headlight bulbs. High color output (approximately 3400 lumens) and gentle effect on the eyes make them an excellent option for the car. This xenon is clearly visible on wet asphalt, but is not very noticeable to fellow travelers.
Regular white (4500-5000 K). This xenon color temperature is considered the optimal option from the point of view of perception by the human eye. They have a high color output power (about 3000 lumens), which significantly expands the scope of application of such lamps.
Cool white, white-blue (from 6000 K). Depending on the type of optics (lensed or reflective), the tint has a greater or lesser degree of blue. Such lamps are inferior to warmer ones on wet asphalt, but on dry ground or snow they provide excellent visibility.
Blue, blue-violet (from 8000 K). Such lighting sources can be classified as decorative. They are not particularly distinguished by their emission power (up to 2200 lumens) and are poorly visible on any road surface.

According to surveys over the past few years, the majority of car enthusiasts preferred xenon lamps with a color temperature of 6000 K. Lanterns should be selected based on personal comfort; it is impossible to clearly name the optimal temperature, because trips to the office and long country trips dictate completely different requirements.

When color temperature is important

Most characteristics of lighting sources should be considered inseparably from each other. Color temperature is inseparable from brightness, because this is the only way to choose the optimal lighting source for any situation. It is also worth starting from how exactly this or that lamp will be perceived, which is equally important for lighting interiors and exteriors, automotive, street and advertising lighting systems.

To choose the optimal LED lamp or LED lamp for yourself, you need to know about some parameters that are key when choosing. And in addition to power, voltage and other things, this parameter is color temperature. That's what we'll talk about here.

Roughly speaking, color temperature is the color of the lighting equipment. Typically, designations of color temperature go within the concepts of “warm light” and “cold light”, however, these concepts are quite vague, because, firstly, each person perceives the color of the glow in their own way, depending on their vision, and secondly, different manufacturers declare the concepts of “cold”, “warm” or “neutral” light for different color temperatures, that is, the number in Kelvin will be the most accurate characteristic of the color temperature of the lamp. To understand what these numbers mean, you need to delve a little into the very nature of the concept, and don’t forget to look at the tables, where it is clearly written what temperature corresponds to what.

The very concept of color temperature should be considered, knowing what an absolutely black body (hereinafter referred to as the black body) is. The term blackbody itself was introduced into use in 1862 by the great German physicist Gustav Kirchhoff. So, a black body is a physical body that, at any temperature, absorbs all electromagnetic radiation incident on it in all ranges. Moreover, the black body itself can emit electromagnetic radiation of any frequency and visually have a color. The radiation spectrum of an absolutely black body is determined only by its temperature. But the radiation intensity of the black body is determined by the formula of Max Planck, another great German physicist. According to this formula, color temperature is defined as the temperature of the black body at which it emits radiation of the same color tone as the radiation in question.

However, it is much easier to consider such things in practice. Since the blackbody is a physical abstraction, it does not exist in reality; physicists consider the model itself, but for clarity, we can imagine the filament of the most ordinary incandescent lamp. If it is heated to a certain temperature, then it will produce a different shade of glow, in full accordance with the radiation spectrum. Below is a list of which lighting sources we are used to and correspond to this or that color temperature:

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;

3800 K - lamps used to illuminate meat products in a store (have a high content of red color in the spectrum);

4000 K - cold white fluorescent lamp;

4300-4500 K - morning sun and lunchtime sun;

4500-5000 K - xenon arc lamp, electric arc;

5000 K - sun at noon;

5500 K - clouds at noon;

5500-5600 K - photo flash;

5600-7000 K - fluorescent fluorescent lamp;

6200 K - close to daylight;

6500 K is a standard daytime white light source, 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 - an “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.

In practice, it usually happens that all such tables and conclusions based on them are actually inferior to ordinary visual comparison. When choosing an LED lamp, there are several standard color temperatures that you should focus on.

So, for LED lamps, temperatures of 3000K, 4000K, 4500K and 5000K are usually available to choose from. First, 3000K is a warm light, closer to yellowish and old incandescent lamps. All indicators above can be attributed to cold light; 4000K is often called “neutral”.

For LED lamps, the most common and familiar indicator is 5000K; it is this color temperature that is usually considered the most comfortable for office lighting, however, 4000K is often used - a slightly more “yellowish” light adds a kind of coziness to the room. If the question is urgent, and you definitely need an exclusively warm light from a lamp, then it is possible to select lamps with a color temperature of 3000K. The same is true with cold light - in our assortment you will find lamps with a temperature of 6500K - the so-called “daylight” light, however, you need to take into account that at this temperature the light often gives off a little “blue”, so it is advisable to evaluate the glow before purchasing “ by eye." Your subjective feelings will be more accurate than any tables, because the color temperature of a lamp is purely a matter of taste!