What is luminous flux in lumens. What are lumens, luxes, kelvins, watts as applied to lighting

To ensure that any task is completed quickly and efficiently production task, the lighting of the specialist’s workplace must be properly organized. For this purpose, lamps with certain photometric indicators are selected.

Lighting in the workplace is determined by various physical quantities, the main one of which is illumination. Its indicators are calculated for the workplace of any specialist and are regulated by the relevant SNiPs.

Illumination is a characteristic that is defined as the luminous flux per unit area.

Luminous flux (F)

The physical parameter is defined as the visible radiation power of a source or the light energy that is emitted by a lamp per unit time.

At the same time, light energy is energy that spreads in all directions and causes visual sensations. Each person has different visual sensations to the same radiation sources, so averaged indicators are taken for calculations.

In physics, the formula is used for calculation:

Ф = W/t, where:

W – energy emitted by the source, measured in watts,
t – operating time of the device in seconds.

It is also a quantity that characterizes the amount of light emitted by a lighting fixture in all directions.

Thus, the second calculation formula looks like:

Ф = I w, where:

I – luminous intensity, measured in candelas,
w – solid angle, calculated in steradians.

Lumen

The unit of measurement for luminous flux is lumen.

In order to determine which source is more profitable to purchase, let’s first consider what a lumen is.

The word lumen in Latin means light.

A lumen is defined as the luminous flux that is emitted by a point source having a luminous intensity of 1 candela per solid angle equal to 1 steradian:

1lm = 1W / 1s.

On the other side,The unit of measurement lumen (lm) can be found as:

1 lm = 1 cd · 1 sr.

If the solid angle is 4π radians and the luminous intensity is 1 cd, then in this case we speak of the total luminous flux, which is equal to 4π lm or 4 3.14 lm.

It was calculated that this indicator for solar radiation corresponds to 8 lm, and starry sky– only 0.000000001 lm.

For any artificial light source there are tables for calculating this photometric parameter.

In lighting engineering, derived quantities are used, which are formed using standard prefixes of the international SI system, for example:

1 klm = 103 lm or 1 klm = 103 lm;
1 Mlm = 106 lm;
1 lm = 10-3 lm;
1 µlm = 10-6 lm.

Measuring instruments

To measure photometric quantities, industry uses special devices called spherical photometers and goniophotometers. They allow you to determine both the luminous flux and the intensity of light from various lamps.

Photometers are either visual or objective.

The principle of operation of visual devices is based on the ability of the eye to determine the same brightness of illumination of two compared surfaces illuminated with the same color.

Currently, objective electric photometers are popular, which allow measuring light parameters not only in the visible zone, but also beyond it.

Goniophotometers allow you to obtain data on the amount of luminous flux, luminous intensity, as well as indicators of other photometric quantities, for example, brightness, illumination distribution, etc.

Recommendations for organizing proper workplace lighting

When lighting workplaces, two types of sources are used: artificial and natural.

Artificial ones are devices with lamps of various types: fluorescent, incandescent, LED, etc.

For each type of lamp, there are tables indicating the number of lumens emitted by a given lamp.

This value is indicated on the product packaging, so when purchasing, be sure to select a light bulb based on the information posted by the manufacturer on the box. The packaging of the lamp indicates the total luminous flux, which includes diffused light.

Attention! When purchasing a lamp, it is important to remember that this indicator does not fully reflect its brightness, since it can be increased through the use of a system of reflectors, lenses and mirrors located in the device.

Selection of electric lamps

Before purchasing light bulbs, you must first choose what devices you need to create the right lighting for your workplace. If the room is rectangular, then the required number of lumens is calculated as follows: you need to multiply the indicators of the illumination standard of the object (determined according to SNiP), the area of the room and the coefficient depending on the height of the ceiling of the room.

Behind last years Approaches to organizing lighting in everyday life and public spaces have changed smoothly and painlessly. Now you won’t surprise anyone with LED lamps.

Stores sell LED and fluorescent lamps, but the buyer continues to keep in mind “power” as the main indicator for lighting sources. Prudent manufacturers, of course, indicate the power on the packaging LED products what could this mean? Should we focus on power and how to determine the correspondence between types of devices?

More information about the level of illumination that an LED light source produces can be found in the lumen output. We’ll look into what lumens mean in LED lamps in this article.

What is a lumen

The concept of lumens was established by the international measurement system in the mid-twentieth century.

Lumens measure the amount of total light emitted by a source. The parameter is directly related to the concept of luxury, but there is a difference between them.

Expert opinion

Alexey Bartosh

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It is important to understand! Lumen is the total amount of light that a source is capable of emitting in all directions. Lux is intended to indicate how much light falls on square meter surfaces.

Therefore, if a lamp emitting 100 Lux illuminates 1 m2 of surface, then a flux of 100 Lux will fall on it. If the same light bulb shines in a room of 10 m2, then its illumination will be significantly lower. It is important to know that the calculations should take into account the entire luminous flux, in all directions.

Understanding this hides one of the advantages of LED devices over incandescent lamps and fluorescent devices that glow in all directions. For diode lamps, the lighting angle approaches 120 or 180 degrees. Using built-in or external lenses, beams of any width are obtained.

LED light bulb from inside

Conclusion: the light flux is directed and used in the desired direction, increasing its concentration.

Manufacturers actively use this feature when developing LED lamps installed instead of halogen and xenon d2s lamps in car headlights. They are cheaper than xenon, put less load on car electrics than halogen ones, and are not inferior in terms of illumination level.

Modern diodes are used to manufacture and replace 20 W lamps in side lights and 55 W lamps in car headlights.

Parameters that determine the luminous flux indicator and its calculation

Several indicators of luminous flux are important for human perception:

The amount of everything coming from a light source.
Wavelength. It determines how the eye perceives the brightness of light. Emission in the middle, green part of the spectrum appears brighter than the blue or red parts, given the same lamp power.
Color temperature is measured in Kelvin and must be indicated on product packaging and data sheets. The picture shows the color temperature scale and the color of the emitted light.

Note! Warm tones are perceived by the human eye as less bright than cool colors. When purchasing “warm” lamps, make a small margin in the direction of increasing the power to create comfortable conditions in the room.

Color temperature in comparison

How many lumens are in 1 W LED bulb?

Finding out the truthful answer to a question is not so easy. The fact is that manufacturers indicate power and luminous flux for LEDs, not light bulbs. Actual values can only be measured with special instruments. You should focus on averages.

In general, when consuming 1 W of power, LEDs emit 90–100 lm. Expensive samples are capable of delivering 130–140 lumens per W.

LEDs producing 220 Lm/W have been obtained in laboratory conditions, but the devices are not produced on an industrial scale due to their high cost.

Reduces the coefficient useful action built-in LED power driver, reducing the luminous flux to power ratio by 5–10%. It is important to take this into account when choosing and purchasing light sources.

Converting lumens to watts

For users who do not want to study the characteristics of electrical appliances and carry out calculations, there are many resources on the Internet with built-in calculators. It is enough to substitute the data provided by the manufacturer (lumens) and select the type of lamp to obtain the required power indicator.

Method for calculating illumination for premises

Calculating the required number of lighting fixtures uses a simple technique.

Calculations are carried out in two stages:

Calculation of the required luminous flux intensity.
Determining the number of lamps capable of providing the required illumination.

Formula for approximate calculation of lighting level, Lm.

Luminous flux = standard illumination indicator in lux (shown in the table) * room area in m2 * ceiling height coefficient.

Table 1. Illumination standards

For ceilings up to 2.7 m, a coefficient of 1 is applied, for room heights from 2.7 to 3 m - a coefficient of 1.2, from 3 to 3.5 m - 1.5.

Calculation example. In children's rooms, the illumination standard is set at 200 Lux. Room area 12 m2 Height 3.1 m - we use a coefficient of 1.2.

Multiplying 200 * 12 * 1.2, we get the required luminous flux of 2880 Lm.

Knowing the light indicator, choose devices capable of providing it. For the given room, one LED lamp with a power of 25–30 W, or three 10-watt sources, is sufficient.

Expert opinion

Alexey Bartosh

Specialist in repair and maintenance of electrical equipment and industrial electronics.

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Important! For better lighting It is wise to use several lamps in a room. This will illuminate the room evenly and get rid of shadows.

Comparative characteristics of an incandescent lamp and an LED lamp

Power usage of different types of light bulbs

When comparing technical characteristics All parameters speak in favor of diode devices.

Table 2. Comparison of LED and LED characteristics.

The regularly decreasing price of LED lamps and the economic benefits of their use make the devices popular among buyers.

How many lumens are there in LEDs relative to other light sources?

Table 3. Average luminous flux for different power consumption.

LED lamps from trusted manufacturers have undeniable advantages for use at home and at work. They are durable, economical, and quickly pay for themselves. The ability to choose any shade of light will make your stay in the room comfortable and safe.

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

What is "luminous flux" called?

First of all, it is worth understanding what this term is called in physics.

Luminous flux is 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 radiation of a light source.

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

Luminous flux unit

How is the physical quantity in question measured?

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

This word was derived 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 a subject of general interest several years ago.

In 1960, the lumen officially began to be used throughout the world as a unit of measurement of luminous flux, and remains so to this day.

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

It is worth noting that in many countries the light power of light bulbs is measured not in watts (as in the vast expanses of the former USSR), but rather in lumens. In other words, overseas consumers consider not the amount of energy consumed, but the strength of the light emitted.

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

Formula

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

In the form of a formula, it looks like this: 1 lm = 1 cd x 1 avg.

Considering that 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 equal to 4P lm.

What is "candela"

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

This name was derived from the Latin word for “candle” (candela). From 1979 to this day it is according to the SI (International System of Units).

In fact, one candela is the intensity of light emitted by one candle (hence the name). It is worth noting 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 paragraph it is clear that lumen and candela are related (1 lm = 1 cd x 1 sr).

Lumens and Luxes

When considering the features of such a light value as a lumen, it is worth paying attention to such a close concept as “lux” (lx).

Like candelas and lumens, luxes also refer to lighting units. Lux is a unit of illumination used in the SI system.

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

Speaking more in simple language, a lumen is a measure of the amount of light emitted by a particular source, such as the same light bulb. But lux shows how light the room really is, 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 actually reached the illuminated surface.

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

For example, when the library hall was built, many light bulbs 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 light bulbs, as before, produced the same amount of lumens of light energy. However, in the path of each of its rays, obstacles now appeared in the form of shelves with books and other library furniture, as well as visitors and workers. Thus, they absorbed part of the emitted light, reducing the total amount of illumination to the hall.

The situation given as an example is not an exception of its kind. Therefore, when constructing any new buildings or decorating the interior of existing ones, it is always important to take into account its illumination. For most institutions there is even a system of lighting standards; naturally, it is measured in lux.

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

Lumen and Watt

In the past, in our country, when choosing a light bulb, we were guided by the number of watts it consumes. The more of them, the better the light of this device.
Today, even in our country, radiation power is increasingly 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 SI units.

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

Eg, ordinary lamp incandescent, consuming 100 watts, produces light of 1340 lumens. At the same time, its more advanced (today) LED “sister” produces 1000 lm while consuming only 13 W. Thus, it turns out that the light intensity of a light bulb is not always directly dependent on the amount and power of energy absorbed by it. Important role The substance used for lighting in the device also plays a role in this matter. This means that there is no direct relationship between lumens and watts.

Moreover, these quantities are really related to each other. The luminous efficiency of any light source (the relationship between the energy consumed and the amount of light produced) is measured in lumens per watt (lm/W). It is this unit that is evidence of the effectiveness of a particular lighting device, as well as its efficiency.

It is worth noting 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.
Light output of the device (how much watt it consumes and how many lumens it produces).

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.

Multiples of Lumen Units

Lumen, like all its “relatives” in the SI system, has a number of standard multiples and submultiples. Some are used for ease of calculation 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. Thus, the largest multiple unit of lumen - iottalumen - is equal to 10 24 lm. It is most often used to characterize cosmic bodies. For example, the luminous flux of the Sun is 36300 Ilm.

The most commonly used units are four multiples: kilolumen (10 3), megalumen (10 6), gigalumen (10 9) and teralumen (10 12).

Lumen subunits

The smallest subunit of a lumen is the ioctolumen - ilm (10 -24), however, like the 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).

When choosing an LED lamp, pay attention to the lumens to ensure the amount of light you need.

We usually buy things based on the quantity we need, right? When we buy milk, we buy it in liters. Then why should it be different with light? For decades, we've bought light bulbs based on how much energy they use (watts)—and without regard to how much light they give us (lumens).

Lumen measures how much light you get from a light bulb. The more lumens, the brighter light. Fewer lumens produce less light.

But the brightness and number of lumens can vary greatly, so there is a certain way calculation of suitable characteristics.

Practical calculation method:

to replace a 100-watt incandescent bulb, look for an LED bulb that produces 1,100 lumens;
75-watt lamp - about 750 lumens;
60-watt lamp - about 550 lumens;
A 40-watt lamp is about 200 lumens.

If you need something less bright, purchase LED bulbs with fewer lumens.

Lighting efficiency:

But we must not forget that Lumen is the total light flux from the source. However, this measurement usually does not take into account the focusing efficiency of the reflector or lens and is therefore not a direct parameter for assessing brightness or useful performance lamp beam. A wide beam of light can have the same lumens as a narrowly focused beam. Lumens cannot be used to determine the intensity of a beam because the lumen rating includes all scattered and wasted light.

Lux is a unit of measurement of illumination.

For example, 1 Lux is equal to the illumination of a surface with an area of 1 m² when the luminous flux of radiation incident on it is equal to 1 lumen. If you collect 100 lumens and project them onto an area of 1 m², the illumination of that area will be 100 lux. If the same 100 lumens are directed at 10 m², the illumination will be 10 lux.

Label for LED lamps:

What should be on the package when you buy LED devices lighting?

To help consumers better understand the transition from watts to lumens, Fed. trading commission proposed a new label for LED lamps. This label will help people buy light bulbs that are right for them.

Just like food labels, lighting labels can help consumers understand what they are really buying. The label clearly indicates: luminous flux, type of bulb, price, estimated cost of operation per year and color of the glow from warm white (with a yellowish tint) to cool white to cold (with a blue tint).

Lumen is a unit of measurement for the brightness of radiation. Is a light quantity in international system units. Lumen characterizes the amount of light emitted by a source. It is a more accurate value than power, since light sources with the same power but different efficiencies and spectral characteristics, emit an unequal amount of light.

What is a lumen?

There are several units for measuring illumination. The main values are lux and lumen. Their difference is that lux shows the illumination of a unit surface area, and lumen is a unit of measurement of the entire radiation flux of a light source. Thus, the higher the lux value, the brighter the surface is illuminated, and the higher the lumen, the brighter the lamp itself. This difference helps evaluate the effectiveness of lighting devices of various designs.

It is necessary to consider what lumens are in LED lamps. This will help to understand the fact that such light sources are characterized by directional radiation. Incandescent and fluorescent lamps emit light in all directions. To obtain the same surface illumination, LED elements of lower brightness are required, since the radiation is concentrated in one direction.

Incandescent and energy-efficient lamps produce non-directional radiation, which requires the use of reflectors (reflectors) that redirect the flow of light in the required direction. When using LED devices, there is no need for reflectors.

Parameters that determine the luminous flux indicator and its calculation

Lighting parameters are affected not only by the brightness level of lighting sources. Should be taken into account:

The wavelength of the emitted light. Lighting with 4200 K, which corresponds to natural white color, is better perceived by vision than those closer to the red or blue part of the spectrum.
Direction of light propagation. Narrowly focused lighting devices allow you to concentrate light emission in in the right place without installing brighter lamps.

Luminous flux in lumens is rarely indicated by manufacturers, since most buyers are guided by the power of the lamps and their color temperature.

How many lumens in 1 W LED light bulb

Manufacturers of lighting equipment do not always include a complete list of characteristics on product packaging. This could be for several reasons:

the habit of buyers to evaluate the brightness of light bulbs by power consumption;
Unscrupulous manufacturers do not bother to take the necessary measurements.

The problem is that the level of radiation from LEDs and structures made on their basis is unequal:

part of the flow is delayed by a protective flask;
There are several LEDs in an LED lamp;
part of the power is dissipated on the LED driver;
Brightness depends on the amount of current through the LED.

An accurate determination is only possible using measuring instruments(lux meters), but for some types of LEDs it will be possible to give approximate data:

LEDs in a frosted bulb – 80-90 Lm/W;
LEDs in a transparent bulb – 100-110 Lm/W;
single LEDs – up to 150 Lm/W;
experimental models - 220 Lm/W.

The listed data can be used to determine the current consumption when using LED devices for which the brightness value is determined. If an LED floodlight with transparent protective glass and its brightness parameter is stated as 3000 lumens, then the power consumption will be 30 W. Knowing the power and supply voltage, it is easy to determine the current consumption.

Converting lumens to watts

To compare the efficiency of light sources various types and structures, it is convenient to have in front of you a table that contains data on the power of lighting devices with the same values brightness.

Residential lighting standards

Indoor illumination for various purposes not the same and can differ by an order of magnitude. The number of lumens per square meter by type of residential premises is as follows:

office, library, workshop – 300;
children's room – 200;
kitchen, bedroom – 150;
bathhouse, sauna, swimming pool – 100;
wardrobe, corridor – 75;
hall, corridor, bathroom, toilet – 50;
staircase, basement, attic – 20.

Calculation of illumination for premises

To determine the illumination of a room, you need to know the following parameters:

E – standard value of illumination (how many lumens are needed per 1 square meter).
S – area of the room.
k – height coefficient:
- k = 1 with a ceiling height of 2.5 – 2.7m;
- k = 1.2 with a ceiling height of 2.7 – 3.0 m;
- k = 1.5 with a ceiling height of 3.0 – 3.5 m;
- k = 2 with a ceiling height of 3.5 – 4.5 m;

The formula for calculation is simple:

Knowing the illumination, you can select the required luminous flux and power lighting lamps taking into account their differences in production technologies and operating principles. One should take into account the peculiarities of human vision for whom light sources with a bluish tint (starting from color temperature 4700K and above) appear less bright.

Comparative characteristics of an incandescent lamp and an LED lamp

Above was a table that compared the power of different types of devices for the same brightness value. The table shows how many lumens are in an incandescent lamp, in fluorescent and LED lamps.

The efficiency of devices varies by more than an order of magnitude. It is immediately clear that the comparison is in favor of modern light sources. And that doesn't even take into account the great durability. LED sources lighting. According to some manufacturers, the lifespan of LED elements can be tens of thousands of hours. Energy savings pay for themselves many times over over their service life high cost LED light sources.

100 W incandescent lamps are the most suitable for lighting domestic premises. Unsatisfactory efficiency and low service life have led to the fact that light sources with incandescent filament are being replaced by more modern, efficient and durable devices. LED lamp 12 W gives the same brightness as lumens in a 100 Watt incandescent lamp.