How is the brightness of light lumens measured. Brightness of projectors - ANSI-lumens and "Chinese" lumens. What is Kelvin in Lighting

Per last years approaches to the organization of lighting in everyday life and public premises have changed smoothly and painlessly. Now you won't surprise anyone with LED lamps.

Stores sell LED and fluorescent fixtures, but the buyer continues to keep "wattage" in mind as the main metric for lighting sources. Forward-looking manufacturers, of course, indicate the wattage on the packaging of LED products, what that might mean. Is it worth focusing on power and how to determine the correspondence between the types of devices?

More about the level of illumination that an LED light source produces is the radiation indicated in lumens. What do the lumens mean in LED lamps, we will figure it out in this article.

What is Lumen

The concept of lumens was established by an international measurement system in the middle of the 20th century.

Lumens measure the amount of total light emitted from 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 (lumen) - the total amount of light that a source is able to emit in all directions. Lux is meant to represent how much light hits a square meter of surface.

Therefore, if a lamp emitting 100 Lm illuminates 1 m2 of surface, then a flux equal to 100 Lx will fall on it. If the same light bulb shines in a room of 10 m2, then its illumination will be much 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, which glow in all directions. In diode lamps, the illumination angle is close to 120 or 180 degrees. With the help of built-in or external lenses, beams of any width are obtained.

LED bulb inside

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

Manufacturers are actively using this feature in the development of LED lamps installed instead of halogen and xenon, d2s lamps, devices in car headlights. They are cheaper than xenon, less load on the electrics of cars than halogen ones, and are not inferior in terms of illumination level.

Modern diodes are used for the manufacture and replacement of 20 W lamps in marker lights and 55 W 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 emanating from the light source.
Wavelength. How the eye perceives the brightness of light depends on it. Radiation in the middle, green part of the spectrum appears to be brighter than blue or red areas for the same lamp wattage.
Color temperature is measured in Kelvin and must be indicated on packages and product passports. 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 cold colors. When buying "warm" lamps, make a small margin in the direction of increasing power to create a comfortable environment in the room.

Comparison of color temperature

How many lumens in 1 W LED light bulb

Finding the true answer to a question is not easy. The fact is that manufacturers indicate power and luminous flux for LEDs, not bulbs. Actual values can only be measured with special devices. It is worth focusing on average indicators.

In general, when 1 W of power is consumed, LEDs emit 90–100 lm. Expensive samples are capable of "giving" 130-140 lm from one watt.

In laboratory conditions, LEDs producing 220 lm / W were obtained, but devices are not produced on an industrial scale due to their high cost.

The built-in LED driver reduces the efficiency, reducing the luminous flux-to-power ratio by 5-10%. It is important to keep this in mind 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 luminaire in order to obtain the required power indicator.

Method for calculating illumination for rooms

The calculation of the required number of lighting fixtures is a simple technique.

Calculations are carried out in two stages:

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

Formula for the approximate calculation of the illumination level, Lm.

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

Table 1. Standards of illumination

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

Calculation example. In the nursery, the illumination standard is set at 200 Lx. Room area 12 m2 Height 3.1 m - we apply a coefficient of 1.2.

Multiplying 200 * 12 * 1.2, you get the required luminous flux of 2880 lm.

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

Expert opinion

Alexey Bartosh

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

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Important! For better lighting the premises are wise to use several lamps. This will light up the room evenly and get rid of the shadows.

Comparative characteristics of incandescent lamp and LED lamp

The use of power by different types of bulbs

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

Table 2. Comparison of characteristics of LED and.

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

How many lumens are in LEDs in relation to other light sources

Table 3. Average indicators of luminous flux for different power consumption.

LED lamps from proven manufacturers have undeniable advantages when used in everyday life and at work. They are durable, economical, and quickly pay off. The ability to choose any shade of glow will make your stay in the room comfortable and safe.

Creation in the house favorable conditions for a normal rest requires taking into account all possible parameters and nuances. Particular attention must be paid to the level of illumination. After all, it is on this parameter that the general health of a person, his emotional and psychological comfort depends.

Therefore, it is very important to calculate how many lumens in lighting are needed per square meter? You will learn about this and about what level of illumination you need to create from our article.

Important parameter

Illumination is a very important indicator, without which a comfortable stay in any room of the house is impossible. Each room in the house has its own light standards. Therefore, various kinds of calculations that relate to this norm are a necessity.
In this situation, you need to make the following calculations:

number of lamps per square meter;
the number of lighting fixtures per square meter;
how many lumens are needed to illuminate a room per square meter.

In this article, we will focus on the last calculation.

What you need to know

When determining how many bulbs or lighting fixtures are needed, the first step is always to calculate the number of lumens per square meter for a particular room.
In this case, you need to know what illumination levels are set for each specific residential or non-residential premises... All these norms are given in special documentation - SNiP.

Norms for SNiP

You can create the desired level of illumination using various sources Sveta:

incandescent lamps;
fluorescent and LED bulbs;
halogen and metal halide lamps;
LED strips;
neon lamps, etc.

Each of the above light sources has different technical indicators of illumination. The most important parameter in assessing the level of illumination is the luminous flux emitted by the light source.
The power values of lighting devices indicated in the table are given for incandescent lamps, since these basic regulatory documents were developed even before the era of modern energy-saving technologies. Today, ordinary incandescent lamps are practically not found in the house. They were replaced by light-emitting diode (led), fluorescent and halogen light sources. At the same time, it is LED bulbs that are most popular, since they are very economical in terms of electricity consumption, have better technical indicators and a longer service life than other energy-saving light sources.
Luminous flux is measured in lumens. The value of the luminous flux can be found on the packaging of the light bulbs. At the same time, it is not always correct to pose the question of how many lumens are needed to illuminate one square meter. This is due to the fact that the luminous flux in this case reflects only the specific capabilities of a particular light source. In this case, taking into account the distance from the selected lighting object for the room is not taken into account. Therefore, it is rational to introduce such a parameter as lighting here. It is measured in suites.

Based on this, equality was established between suites and lumens. Thus, by one meter square area room has a luminous flux of one lumen and it is equal to one lux. This rule applies to all premises, both residential and non-residential.

Note! With distance from the light source, there is a proportional decrease in illumination per square of the distance.

Required volumes

After we figured out the concept of illumination and put an equal sign between lumens and lux, we can begin to determine the illumination rate for the average person. Physicians and psychologists worked on this issue, who developed the necessary indicators of the level of illumination for each room and room in the house. All of them are given in the SNiP table.

Note! All norms given in this documentation are recommended. In addition, they are minimal and for residential premises they can undergo certain changes in the established range. At the same time, the changes should be minimal, so as not to affect the human body in a negative way. This range is 10-50 lux.

Indicators for the apartment

The existing standards allow you to create a comfortable level of lighting. They are listed in suites, which can be specified in lumens if desired.
To calculate the number of lumens, you need to be guided by indicative methods. Using the parameters indicated in the table, you can roughly estimate the number of lumens that is needed to illuminate one square meter of a room with a ceiling height of about three meters.

Calculations for different lamps

The calculation of the number of lumens required to illuminate one square meter of space, depending on what standards exist for a particular room, directly depends on the choice of a light source.
Determining the type and number of light sources is the most important task for any apartment owner. To assess the required level of illumination and other indicators (type of bulbs and their number), you need to evaluate the following parameters:

room area;
power of purchased bulbs;
norms of SNiP.

Types of lamps

In a situation where you bought energy-saving light sources (fluorescent, LED, etc.), when calculating one square meter of room area, you must take into account the corresponding coefficients.
For fluorescent lamps, the number of watts per square meter should be reduced by about 3.5-4.5 times. But if LED lamps are used - 6-8 times at once. This situation has arisen due to the fact that modern energy-saving light bulbs have a much higher luminous efficiency compared to incandescent paws. As a result, with significantly less power consumption, such products will give a much brighter light. Therefore, their number will need to be reduced in proportion to the increase in the level of light output.

Power table

In addition, it must be remembered that in this situation it is also necessary to evaluate the height of the ceilings. Today people live both in new buildings and in old Khrushchev buildings. And the height of the ceilings is different. With ceilings of three meters, the number of watts and lumens will need to be increased by at least 1.5.

Important points

To make a professional calculation of the illumination level and the number of required lumens, the following points must be taken into account:

lamp type;
the height at which the lighting fixture will be placed;
type of lamp;
its location in the room relative to the vertical plane. Here the efficiency of the lighting device should be evaluated;
reflective characteristics of the material used for interior decoration of the premises: walls, floor and ceiling.

When determining the reflectivity of walls, ceilings and floors, it must be remembered that the brighter the room is, the higher the amount of light reflection will be:

if the ceiling and walls are made in light colors, then the coefficient of light reflectance will be approximately 0.7;
when decorating a room with light, beige and light gray facade paints, this coefficient will be approximately 0.5-0.6;
for dark colors – 0,3;
when decorating a room with black granite or marble, the reflectance will be approximately 0.1.

To calculate the optical characteristics of a room, use the efficiency parameter and special unified tables.

Note! In the absence of the desire or ability to independently produce lumens to determine the level of illumination, you can use the services of specialized offices.

They will be able to quickly make the necessary calculations, eliminating possible mistakes or error.

We carry out calculations

To determine the illumination for a surface (in lux), as well as the luminous flux (in lumens), several calculation steps should be performed:

calculation of the total value of the luminous flux indicator required in a particular room;
then, based on the numbers obtained, you need to determine the required number of light sources, depending on their power.

In order to determine the luminous flux indicator (in lumens), you should use a special formula - "luminous flux = X * Y * Z", where:

X is the norm established for the illumination of a particular room / object. To do this, follow the SNiP table given in our article the very first;
Y - area of a specific room (indicated in square meters);
Z is a correction factor that is entered depending on the height of the ceilings in the room for which the calculations are carried out. If the ceiling height will be from 2.5 to 2.7 meters, then the coefficient is taken as equal to one. If there are ceilings from 2.7 to 3 meters, the coefficient = 1.2. If you are the proud owner of ceilings from 3 to 3.5 meters, then the coefficient = 1.5. Rarely, but ceilings can be from 3.5 to 4.5 meters. In such a situation, the coefficient will be equal to 2.

Ceiling height is important

Substituting all the values in the formula, you get the number of lumens that you need per square meter of a particular room.
After that, you need to complete the calculations by determining the number of bulbs and lamps that should be installed in the room in order to obtain a high-quality and comfortable level of illumination. To do this, you need to be guided by the table, which shows the indicators of the luminous flux power for the LED lamp. We settled on an LED light source, as it is today that it is most often used for indoor lighting.

Luminous flux power indicator table

The value that we got at the first stage must be divided by the luminous flux of the lamp used (taken from the table) and you will get the required number of LED lamps of this power for the room.

Good to know

If you get a non-integer value (for example, 3.75), it must be rounded up. A slight excess of the norm will be better than a lack of it.
Better lighting will be with the even placement of lighting fixtures around the entire perimeter of the ceiling. In such a situation, as well as with some special design approach to lighting fixtures, you can take a larger number of bulbs, but with less power. For example, instead of 4 10 W lamps, you can take 9 5 W lamps.
As you can see, the calculations themselves are quite simple, but in order to carry them out, you need to understand the nature of illumination and what affects it. Having calculated everything correctly, you can create a comfortable level of illumination in any room of the house.

Solving the problem of flickering LED strips in the on state

Light flow- the power of light radiation, i.e., 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 a 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 = 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 0.5305 mm 2 at the solidification temperature of platinum (1773 ° C), or 1 candle · 1 steradian.

The power of light- the spatial density of the luminous flux, equal to the ratio of the luminous flux to the solid angle in which the radiation is uniformly 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 the luminous flux of 1 lm, evenly distributed over an area of 1 m 2, that is, 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 projection area of the luminous surface on a plane perpendicular to the same direction.

The unit of brightness is 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 the luminous surface.

The unit of luminosity is 1 lm / m2.

Light units in the international SI system (SI)

Name of quantity	Unit name	Expression through SI units (SI)	Unit designation
Name of quantity	Unit name	Expression through SI units (SI)	Russian	between- folk
The power of light	candela	cd	cd	cd
Light flow	lumen	cd sr	lm	lm
Light energy	lumen-second	cd sr s	lm s	lm s
Illumination	luxury	cd sr / m 2	OK	lx
Luminosity	lumen per square meter	cd sr / m 2	lm m 2	lm / m 2
Brightness	candela per square meter	cd / m2	cd / m2	cd / m 2
Light exposure	lux second	cd sr s / m 2	lx s	lx s
Radiation energy	joule	kg m 2 / s 2	J	J
Radiation flux, radiation power	watt	kg m 2 / s 3	W	W
Luminous equivalent of radiation flux	lumen per watt		lm / W	lm / W
Surface radiation flux density	watt per square meter	kg / s 3	W / m 2	W / m 2
Luminous energy (radiant intensity)	watt per steradian	kg m2 / (s 3 sr)	W / Wed	W / sr
Energy brightness	watt per steradian square meter	kg / (s 3 sr)	W / (sr m 2)	W / (sr m 2)
Energy illumination (irradiance)	watt per square meter	kg / s 3	W / m 2	W / m 2
Energetic luminosity (emissivity)	watt per square meter	kg / s 3	W / m 2	W / m 2

Examples:

ELECTRICAL DIRECTORY "
Ed. professors MPEI V.G. Gerasimova and others.
M .: Publishing house MEI, 1998

Lumen (lm, lm)- unit of measurement of luminous flux in SI. Where SI is a system of units of physical quantities, (fr. Le Syst? Me International d "Unit? S, SI).

One lumen is equal to the luminous flux emitted by an isotropic point source with a luminous intensity of one candela into a solid angle of one steradian (1 lm = 1 cd? Sr). The total luminous flux created by an isotropic source with a luminous intensity of one candela is 4? lumens.

A conventional incandescent lamp with a power of 100 W produces a luminous flux of approximately 1300 lumens. A compact 26 W fluorescent daylight lamp with a luminous flux of approximately 1600 lumens. The luminous flux of the Sun is 3.63 · 10 to the 28th power of lm.

Lumen is the total luminous flux from the source. However, this measurement usually does not take into account the focusing efficiency of a reflector or lens and therefore is not a direct parameter for evaluating the brightness or useful performance of the beam. A wide beam of light can have the same lumen as a narrow beam. Lumens cannot be used to determine the intensity of a beam because the lumen estimate includes all scattered, useless light.

Lux (lx, lx)- unit of measurement of illumination in the SI system.

Lux is equal to the illumination of a surface with an area of 1 square meter with a luminous flux of radiation incident on it, equal to 1 lumen.

100 lumens were collected and projected onto a 1 meter square area. The illumination of the area will be 100 lux. The same 100 lumens aimed at 10 square meters will give an illumination of 10 lux.

Candela (cd, cd)- one of the seven basic units of measurement of the SI system, equal to the intensity of light emitted in a given direction by a source of monochromatic radiation with a frequency of 540 10 to the 12th power of Hz, the energy intensity of which in this direction is (1/683) W / sr. Steradia? N (Russian designation: Wed, international: sr) is a unit of measurement of solid angles.

The selected frequency is green. The human eye is most sensitive in this region of the spectrum. If the radiation has a different frequency, then a higher energy intensity is required to achieve the same luminous intensity.

Previously, candela was defined as the intensity of light emitted by a black body perpendicular to a surface of 1/60 sq cm at the melting point of platinum (2042.5 K). In the modern definition, the factor 1/683 is chosen in such a way that the new definition corresponds to the old one.

The intensity of light emitted by a candle is approximately equal to one candela (Latin candela - candle), so this unit of measurement was previously called "candle", now this name is obsolete and is not used.

Luminous intensity of typical sources:

A source	Power, W	Approximate luminous intensity, cd
Candle		1
Modern (2016) incandescent lamp	100	100
Conventional LED	0,015	5 mcd
Superbright LED	1	25
Super-bright LED with collimator	1	1500
Modern (2016) fluorescent lamp	20	100

Black Diamond is a law firm in the world of professional mountaineering and climbing equipment. The brand produces high quality headlamps and pendant lights that can be used even one meter deep under water for half an hour. BD offers travel lighting with a lumen output of up to 200 lumens at a relatively low weight. Many lights are equipped with several lighting modes for ease of use on a climbing route and at home. Bright, light, neat and practical, BlackDiamond flashlights will not let you down even in the most extreme situations.

Luminous flux of lanterns (lm)

big LED-high, big LED-med, big LED-low, 5 MM - High, 5 MM - medium, 5 MM - low

Flashlight Black Diamond (BD)	Luminous flux, (lm)
Icon	200
Spot new	200
Cosmo new	90
Wiz new	30
Ion	80
Ember power light	150
Orbit lantern	105
Voyager lantern	140
Lantern Petzl	Luminous flux (lm)
Tikka XP	180
MYO XP	140

Light is something without which nothing on Earth could exist. Like everyone else 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 this term in physics.

Luminous flux - the power of light emission, estimated 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, the lumen was officially used around 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 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 a point isotropic 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 = 1 cd x 1 cf.

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, it is worth paying 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 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 = 1 cd x 1 sr).

Lumens & Suites

Considering the features of such a light quantity 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 luxury 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.

In simpler terms, lumen is a measure of the amount of light emitted by a certain 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 the 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, 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 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.

V 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 is emitting.

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 illumination 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 are 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 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.
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 of 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).