Lumen is a unit of measurement. What is "candela". Luminous flux of LED lamps

Light is something without which nothing on Earth could exist. Like all physical quantities, it can be calculated, which means that there is a unit for measuring the luminous flux. What is it called and what is it equal to? Let's find the answers to these questions.

What is called "luminous flux"

First of all, it is worth figuring out what is called by this term in physics.

Luminous flux - the power of light emission, assessed by the light sensation it produces from the point of view of the human eye. This is a quantitative characteristic of the emission of a light source.

The numerically considered value is equal to the energy of the light flux passing through a certain surface per unit of time.

Luminous flux unit

What is the physical quantity under consideration measured in?

According to the current SI (International System of Units) standards, a specialized unit called lumen is used for this.

This word was formed from the Latin noun meaning "light" - lūmen. By the way, this word also gave rise to the name of the secret organization "Illuminati", which became the subject of general interest several years ago.

In 1960, lumen was officially used around the world as a unit of measure for luminous flux, and remains so to this day.

In abbreviated form in Russian, this unit is written as "lm", and in English - lm.

It should be noted that in many countries the light power of light bulbs is measured not in watts (as in the vastness of the former USSR), but in lumens. In other words, overseas consumers do not consider the amount of energy consumed, but the strength of the emitted light.

By the way, because of this, on the packaging of most modern energy-saving bulbs there is information about their characteristics in watts and in lumens.

Formula

The considered unit of measurement of the luminous flux is numerically equal to the light from an isotropic point source (with a force per candela), emitted into a solid angle equal to one steradian.

In the form of a formula, it looks like this: 1 lm \u003d 1 cd x 1 average.

If we take into account that the full sphere forms a solid angle of 4P sr, it turns out that the total luminous flux of the above source with a power of one candela is 4P lm.

What is "candela"

Having learned about what lumen is, you should pay attention to the unit associated with it. We are talking about cd - that is, candela.

This name was formed from the Latin word for "candle" (candela). From 1979 to the present day, it is according to the SI (International System of Units).

In fact, one candela is the luminous intensity emitted by one candle (hence the name). It should be noted that in Russian for a long time, instead of the term "candela", the word "candle" was used. However, this name is outdated.

From the previous point it is clear that the lumen and candela are related (1 lm \u003d 1 cd x 1 sr).

Lumens & Suites

Considering the features of such a light value as lumen, it is worth paying attention to such a close concept as "lux" (lx).

Like candelas with lumens, suites also belong to lighting units. Lx is the SI unit of measure for illuminance.

The relationship between lux and lumen is as follows: 1 lux is equal to 1 lm of luminous flux, evenly distributed on the surface in 1 square meter... Thus, in addition to the above lumen formula (1 lm \u003d 1 cd x 1 sr), this unit has one more: 1 lm \u003d 1 lx / m2.

Speaking more simple languageLumen is a measure of the amount of light emitted by a specific source, for example, the same light bulb. But lux shows how really light it is in the room, since not all light rays reach the illuminated surface. In other words, lumen is the light that came out of the source, lux is the amount of it that really reached the illuminated surface.

As already mentioned, not always all the emitted light reaches the illuminated surface, because often on the path of such rays there are obstacles that create shadows. And the more of them on the way, the less illumination.

For example, during the construction of the library hall, many lamps were hung in it. The total illumination of this empty room was 250 lux. But when the renovation work was completed and furniture was brought into the hall, the light level dropped to 200 lux. This is despite the fact that the bulbs, as before, gave out the same amount of lumens of light energy. However, every ray of it now has obstacles in the form of shelves with books and other library furniture, as well as visitors and workers. Thus, they absorbed some of the emitted light, reducing the total amount of illumination to the hall.

The situation given as an example is no exception. Therefore, when building any new buildings or decorating existing ones, it is always important to take into account its illumination. For most institutions, there is even a system of lighting standards, of course, it is measured in lux.

AT modern world there are several programs in which you can not only model the design of your room yourself, but also calculate how light it will be. After all, the vision of its inhabitants depends on it.

Lumen and watt

In the past, in our country, when choosing a light bulb, they were guided by the number of watts that it consumes. The more, the better the device shone.
Today, even in domestic open spaces, more and more often the radiation power is measured in lumens. In this regard, some believe that lm and W are quantities of the same kind, which means that lumens to watts and vice versa can be freely converted, like some other units of the SI system.

This opinion is not entirely true. The fact is that both considered units of measurement are used for different quantities. So, a watt is not a light, but an energy unit that shows the power of a light source. Whereas the lumen indicates how much light a particular device emits.

For example, a conventional incandescent lamp that consumes 100 watts produces 1340 lumens of light. At the same time, its more advanced (today) LED "sister" with a consumption of only 13 W produces 1000 lumens. Thus, it turns out that the luminosity of a light bulb is not always directly dependent on the amount and power of the energy absorbed by it. The substance used for lighting in the device also plays an important role in this matter. This means that there is no direct relationship between lumens and watts.

In this case, these values \u200b\u200bare really related to each other. The luminous efficiency of any light source (the relationship between energy consumption and the amount of light emitted) is measured in lumens per watt (lm / W). It is this unit that is evidence of the effectiveness of this or that lighting device, as well as its economy.

It should be noted that, if necessary, it is still possible to convert lumens to watts and vice versa. But for this you need to take into account several additional nuances.

• The nature of the light source. Which lamp is used in the calculations: incandescent, LED, mercury, halogen, fluorescent, etc.
• The light output of the device (how many watts it consumes and how many lumens it produces at the same time).

However, in order not to complicate your life, to carry out such calculations, you can simply use an online calculator or download a similar program to your computer or other device.

Multiple lumen units

Lumen, like all its "relatives" in the SI system, has a number of standard multiples and sub-multiples. Some are used for simplicity of calculations when one has to deal with either too small or too large values.

If we are talking about the latter, then they are written in the form of a positive degree, if about the former - in the form of a negative one. So, the largest multiple unit of lumen - iottalumen - is equal to 10 24 lm. It is most often used when characterizing cosmic bodies. For example, the luminous flux of the Sun is 36300 Ilm.

Most often, four multiple units are used: kilolumen (10 3), megalumen (10 6), gigalumen (10 9) and teralumen (10 12).

Fractional lumen units

The smallest fractional lumen unit is ioctolumen - ilm (10 -24), however, like iottalumen, it is practically not used in real calculations.

The most commonly used units are millilumen (10 -3), microlumen (10 -6) and nanolumen (10 -9).

Anyone who begins to study the characteristics of luminaires and certain types lamps, necessarily collides with such concepts as illumination, luminous flux and luminous intensity. What do they mean and how do they differ from each other?

Let's try to understand these values \u200b\u200bin simple, understandable words for everyone. How they are related to each other, their units of measurement and how the whole thing can be measured without special devices.

What is luminous flux

In the good old days, the main parameter by which a light bulb was chosen in the hallway, in the kitchen, in the hall was its power. No one ever thought to ask a store about any lumens or candelas.

Today, with the rapid development of LEDs and other types of lamps, going to the store for new copies is accompanied by a bunch of questions not only about the price, but also about their characteristics. One of the most important parameters is the luminous flux.

Speaking in simple words, the luminous flux is the amount of light that the lamp gives.

However, do not confuse the luminous flux of the LEDs individually with the luminous flux of the assembled luminaires. They can vary significantly.

It must be understood that the luminous flux is just one of the many characteristics of the light source. Moreover, its value depends:

• from source power

Here is a table of this relationship for LED luminaires:

And these are tables of their comparison with other types of incandescent, fluorescent, DRL, DNaT lamps:

Incandescent light bulbFluorescent LampHalogen HPS DRL

However, there are nuances here. LED technologies are still developing and it is quite possible that LED bulbs of the same power, but from different manufacturers, will have completely different luminous fluxes.

It's just that some of them have gone more ahead, and learned to remove more lumens from one watt than others.

Someone asks what are all these tables for? So that sellers and manufacturers do not stupidly deceive you.

The box will be beautifully written:

• power 9W

• light flux 1000Lm

• similar to a 100W incandescent lamp

What will you look at first? That's right, for what is more familiar and understandable - the indicators of an analogue of an incandescent lamp.

But with this power, you won't get anywhere near the old light. Start swearing at LEDs and their imperfection technologies. And then the matter turns out to be in an unscrupulous manufacturer and his product.

• from efficiency

That is, how efficiently a particular source converts electrical energy into light. For example, a conventional incandescent lamp has an output of 15 lm / W, and a sodium lamp high pressure already 150 lm / W.

It turns out that this is 10 times more efficient source than a simple light bulb. At the same power, you have 10 times more light!

The luminous flux is measured in Lumens - Lm.

What is 1 Lumen? During the day in normal light, our eyes are most sensitive to green. For example, if you take two lamps with the same power of blue and green, then for all of us it will be green that will seem brighter.

The green wavelength is 555 nm. Such radiation is called monochromatic because it contains a very narrow range.

Of course, in reality, green is complemented by other colors, so that in the end you can get white.

But since the sensitivity of the human eye is maximal precisely to greenery, the lumens were tied to it.

So, a luminous flux of one lumen, just the same corresponds to a source that emits light with a wavelength of 555 nm. In this case, the power of such a source is equal to 1/683 W.

Why exactly 1/683, and not 1 W for even counting? The value of 1/683 W arose historically. Initially, the main light source was an ordinary candle, and the radiation of all new lamps and lamps was just the same compared to the light from a candle.

At present, this value of 1/683 is legalized by many international agreements and accepted everywhere.

Why do we need such a quantity as a luminous flux? With its help, you can easily calculate the illumination of a room.

This directly affects a person's vision.

The difference between illumination and luminous flux

At the same time, many people confuse Lumens with Lux units. Remember, it is the illumination that is measured in lux.

How can you clearly explain their difference? Imagine pressure and strength. With just a small needle and little force, a high specific pressure can be generated at a single point.

Also, with the help of a weak luminous flux, you can create high illumination in a single area of \u200b\u200bthe surface.

1 Lux is when 1 Lumen hits 1m2 of illuminated area.

Let's say you have a certain lamp with a luminous flux of 1000 lm. There is a table at the bottom of this lamp.

There must be a certain amount of light on the surface of this table so that you can work comfortably. The primary source for the illumination standards are the requirements of the codes of SP 52.13330

For a regular workplace, this is 350 Lux. For a place where fine fine work is done - 500 Lx.

This illumination will depend on many parameters. For example, from the distance to the light source.

From foreign objects nearby. If the table is located near a white wall, then there will be more suites than from a dark one. Reflection will definitely affect the overall bottom line.

Any illumination can be measured. If you do not have special luxometers, use the programs in modern smartphones.

True, prepare for errors in advance. But in order to do an offhand initial analysis, the phone will do just fine.

Luminous flux calculation

And how do you know the approximate light flux in lumens, without any measuring instruments at all? Here you can use the values \u200b\u200bof light output and their proportional relationship to flux.

Light flow - the power of light radiation, that is, visible radiation, estimated by the light sensation it produces on the human eye. Luminous flux is measured in lumens.

For example, an incandescent lamp (100 W) emits a luminous flux equal to 1350 lm, and fluorescent Lamp LB40 - 3200.

One lumen is equal to the luminous flux emitted by a point isotropic source, with a luminous intensity equal to one candela, in a solid angle of one steradian (1 lm \u003d 1 cd sr).

The total luminous flux produced by an isotropic source with a luminous intensity of one candela is 4π lumens.

There is another definition: the unit of luminous flux is lumen (lm), equal to the flux emitted by an absolutely black body from an area of \u200b\u200b0.5305 mm 2 at the solidification temperature of platinum (1773 ° C), or 1 candle · 1 steradian.

The power of light - the spatial density of the light flux, equal to the ratio of the light flux to the solid angle in which the radiation is evenly distributed. The unit of luminous intensity is the candela.

Illumination - the surface density of the luminous flux falling on the surface, equal to the ratio of the luminous flux to the size of the illuminated surface, over which it is evenly distributed.

The unit of illumination is lux (lux), equal to the illumination created by a luminous flux of 1 lm, evenly distributed over an area of \u200b\u200b1 m 2, i.e. equal to 1 lm / 1 m 2.

Brightness - the surface density of the luminous intensity in a given direction, equal to the ratio of the luminous intensity to the area of \u200b\u200bthe projection of the luminous surface on the plane perpendicular to the same direction.

The unit of luminance is the candela per square meter (cd / m2).

Luminosity (luminosity) - the surface density of the luminous flux emitted by the surface, equal to the ratio of the luminous flux to the area of \u200b\u200bthe luminous surface.

The unit of luminosity is 1 lm / m2.

Light units in the international SI system (SI)

Examples:

ELECTRICAL DIRECTORY "
Ed. professors of MPEI V.G. Gerasimova and others.
Moscow: MEI Publishing House, 1998

Illumination is the most common photometric value, in everyday life it is defined in simple terms: light, dark, twilight, etc. The level of illumination has a significant impact on a person's well-being and ability to work, his ability to receive information from a variety of sources with the help of sight. To create comfortable conditions, it is necessary to measure the illumination and determine the optimal values.

Illumination concept

Determination of illumination is impossible without using other parameters of visible light - light units:

• Candela (cd). Luminous intensity refers to basic units international system SI. The previously used name is a candle that served as a reference for measurements. Now one candela is the luminous efficiency of a monochrome emitter at a strictly defined frequency, with a given energy. In domestic use, one candela corresponds to the luminous intensity of one ordinary candle, 100 cd - an incandescent lamp with a power of 100 W;
• Luminous flux - lumen (lm), a derived unit. The definition is closely related to the intensity of light. 1 lumen is the luminous flux of the emitter with a force of one candela, distributed in one steradian (solid angle): 1 lm \u003d 1 cd ∙ 1 sr. Typical values \u200b\u200bfor 100W incandescent bulbs with a transparent bulb are 1300-1400 lumens.

Illumination depends on these characteristics of the light source and indicates the amount of luminous flux incident on a certain area, measured in lux (lx). Lux is taken as a unit of illumination - this is a luminous flux of one lumen, falling perpendicular to 1 m2 of the illuminated area and evenly distributed over it. It is also defined as the illumination of a sphere with a radius of 1 meter, located inside an emitter with a luminous intensity of 1 cd. It is directly proportional to the intensity of the source and inversely proportional to the square of the distance to it. The source is taken to be an isotropic point emitter that uniformly emits light in all directions.

The calculation of the specific value of candelas, lumens and lux is made according to the formulas:

E \u003d F / S, where E is illumination, lux; S - area, m2.

E \u003d I / R2, where R is the distance to the source.

From these ratios it is clear how to convert suites to lumens, calculate the required flow at a certain illumination:

F \u003d E × S, where F is the desired luminous flux in lumens, E is the known illumination, lux, S is the area, m2.

The value decreases in the event that the light falls at an angle, then the result must be multiplied by the value of the cosine of the angle of incidence of the rays:

E \u003d (F / S) × cos i;

E \u003d (I / R2) × cos i.

In traditional English and American measurement systems, the concept of foot - candela is used. It is defined as the illumination at a distance of one foot produced by a source of one candela luminous intensity. More than one suite is approximately ten times, it is convenient to use online calculators for conversion.

Average values \u200b\u200bfor some common natural and artificial light sources:

• Sun, at mid-latitudes, noon - up to 400,000 lux;
• Cloudy weather - 3000 lux;
• Sunrise - 1000 lux;
• Full moon without clouds - up to 1 lux;
• Stadium under artificial lighting - up to 1300 lux.

The indicated values \u200b\u200bare approximate and cannot be used for calculations - the difference in measurements can be very large.

Primary requirements

The illumination of any object on which the luminous flux falls does not depend in any way on its properties - they determine only the reflectivity of the surface, which is commonly called luminosity or brightness. Reflected light from ceilings, mirrors, and other structures is often used to enhance the efficiency of primary lighting, as most pendant lighting designs provide for a portion of the light to be directed towards the upper hemisphere.

• Living room - 200 lux;
• Bathroom, shower room - 80 lux;
• Cabinet - 300 lux;
• Utility rooms - 50 lux.

For production and service facilities, standardized values \u200b\u200bhave been established, specified in the SNiP rulebook.

Lighting is calculated using cumbersome formulas, which include many parameters: lux and lumens, area, various coefficients, how many lamps, etc. For simple applications, there are many calculators on the Internet that greatly facilitate calculations.

Measurement

Direct measurement of illumination is carried out with a special device - a luxmeter, which displays the result directly in lux. Works on the principle of the photoelectric effect inherent in some materials: a selenium element or semiconductors. In photography, exposure meters are used, which give the result in exposure numbers EV.

The light meter registers the luminous flux in a specific place, taking into account all types of lighting: artificial, natural, reflected.

Light source designations

The ability of a lighting product to create a certain level of illumination is indicated as the value of the luminous flux in lumens.

Characteristics of the main indicators as applied to lighting: suites, lumens, kelvin, watts. Read on!

Given the current economic situation in our country, now is the time to switch to LED lighting. Why? LED lamps consume much less electricity compared to other light sources, and in their technical characteristics they are much superior to, for example, the same incandescent lamps.

However, before you go to the LED equipment store, you need to know some of the characteristics of such devices, taking into account which you can choose exactly the lighting device whose characteristics will fully meet the operating conditions. In this article, we will talk about what watts, lumens, lux and kelvin mean on LED markings, and also talk about the advantages of LED devices over other light sources.

Watts, Lux, Lumens, Kelvin as the main characteristics of LEDs

When buying incandescent lamps, the consumer is guided by the number of watts indicated on the label, thereby determining how bright the product will shine. In LEDs, this figure has a completely different meaning.

The number of watts indicated by the manufacturer on the packaging does not characterize the brightness of the device, but the amount of electricity consumed per hour of operation. Naturally, you can draw a parallel between incandescent lamps and LEDs, focusing only on power. There are even special tables for this. So, for example, an 8-12 watt LED device will shine as brightly as an incandescent lamp with a 60 watt characteristic. However, the main unit that determines brightness lED lamps, is the lumen.

What are lumens in LED bulbs

By lumen is meant the amount of luminous flux that is emitted by the illumination source with a force equal to one candela per angle of one steradian.

For example! An incandescent lamp with a power of 100 W is able to create a luminous flux equal to 1300 lumens, while a much lower power LED is able to produce a similar indicator.

However, in addition to lumens, LED equipment is also characterized by the amount of illumination, which is measured in lux.

What is Lux in Lighting

Lux is a unit of measure for illuminance, which equals the illuminance of a surface of one square meter with a luminous flux equal to one lumen. So, for example, if you project 100 lumens onto an area of \u200b\u200b1 square meter, then the illumination index will be 100 lux. And if a similar luminous flux is directed over ten square meters, then the illumination will be only 10 lux.

Now, when you are asked: "suites and lumens, what is the difference?", You can show off your knowledge and give the interlocutor an exhaustive answer to his question.

What is Kelvin in Lighting

As you may have noticed, incandescent light has a warm yellowish tint, while LEDs have a wide color gamut. So, LED equipment is capable of displaying colors from violet to red (in the spectrum of white and yellow colors). However, the most common colors are bright white, soft or warm white. Why are we telling you this? The thing is that you can determine the color of light by marking the product. To do this, you need to look at such technical characteristics as color temperature, which is measured in Kelvin. The lower the number, the more yellow (warmer) the light will be emitted.

For example, a typical incandescent light bulb has a color temperature that ranges between 2700 Kelvin and 3500 Kelvin. Thus, if you are looking for an LED lighting fixture that has the same color as an incandescent lamp, choose an LED fixture with a similar color temperature.

Various types of industrial lamps, their advantages and disadvantages

Below is given comparison table various types of industrial lamps.

Based on this table, we can conclude that LED lamps are superior to other types of lighting elements in almost all respects. As for the price, this factor can hardly be called a significant drawback. In addition, with the question of choosing and installing LED equipment, for example, it will pay for itself in a relatively short time.

Consult about technical characteristics and LED industrial lamps, as well as choose from the product you need, you can on our website. Also, our specialists will carry out the current lighting at your facility and offer a suitable system for modernization.

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