It follows from the definition that the value for the frequency 540⋅10 12 Hz is 683 lm / W = 683 cd sr / W exactly.

The selected frequency corresponds to a wavelength of 555.016 nm in air under standard conditions and is close to the maximum sensitivity of the human eye, located at a wavelength of 555 nm. If the radiation has a different wavelength, then a greater energy intensity of light is required to achieve the same luminous intensity.

Detailed consideration[ | ]

All light quantities are reduced photometric quantities. This means that they are formed from the corresponding energy photometric value by means of a function representing the dependence of the spectral luminous efficiency of monochromatic radiation for daytime vision on the wavelength. This function is usually represented as K m ⋅ V (λ) (\displaystyle K_(m)\cdot V(\lambda)), where is a function normalized so that at the maximum it is equal to unity, and is the maximum value of the spectral luminous efficiency of monochromatic radiation. Sometimes K m (\displaystyle K_(m)) also called the photometric equivalent of radiation.

Light value calculation X v , (\displaystyle X_(v),) the corresponding energy quantity is produced using the formula

X v = K m ∫ 380 nm 780 nm X e , λ (λ) V (λ) d λ , (\displaystyle X_(v)=K_(m)\int \limits _(380~(\text(nm) ))^(780~(\text(nm)))X_(e,\lambda )(\lambda)V(\lambda)\,d\lambda ,)

where X e , λ (\displaystyle X_(e,\lambda ))- spectral density of quantity X e , (\displaystyle X_(e),) defined as the ratio of the magnitude d X e (λ) , (\displaystyle dX_(e)(\lambda),) falling on a small spectral interval between and λ + d λ , (\displaystyle \lambda +d\lambda ,) to the width of this interval:

X e , λ (λ) = d X e (λ) d λ . (\displaystyle X_(e,\lambda )(\lambda)=(\frac (dX_(e)(\lambda))(d\lambda )).)

It may be noted that under X e (λ) (\displaystyle X_(e)(\lambda)) here we mean the flux of that part of the radiation whose wavelength is less than the current value λ (\displaystyle \lambda ).

Function V (λ) (\displaystyle V(\lambda)) determined empirically and given in tabular form. Its values ​​do not depend on the choice of light units used.

Contrary to what was said about V (λ) (\displaystyle V(\lambda)) meaning K m (\displaystyle K_(m)) is entirely determined by the choice of the main light unit. Therefore, to establish a connection between light and energy quantities in the SI system, it is required to determine the value K m (\displaystyle K_(m)) corresponding to the SI unit of luminous intensity, the candela. With a strict approach to the definition K m (\displaystyle K_(m)) it must be taken into account that the spectral point 540⋅10 12 Hz, which is referred to in the definition of the candela, does not coincide with the position of the maximum of the function V (λ) (\displaystyle V(\lambda)).

Luminous efficiency of radiation with a frequency of 540⋅10 12 Hz[ | ]

In general, the intensity of light is related to the intensity of radiation I e (\displaystyle I_(e)) ratio

I v = K m ⋅ ∫ 380 nm 780 nm I e , λ (λ) V (λ) d λ , (\displaystyle I_(v)=K_(m)\cdot \int \limits _(380~(\text (nm)))^(780~(\text(nm)))I_(e,\lambda )(\lambda)V(\lambda)\,d\lambda ,)

where I e , λ (\displaystyle I_(e,\lambda ))- spectral density of the radiation force, equal to d I e (λ) d λ (\displaystyle (\frac (dI_(e)(\lambda))(d\lambda ))).

For monochromatic radiation with a wavelength λ (\displaystyle \lambda ) formula relating the intensity of light I v (λ) (\displaystyle I_(v)(\lambda)) with radiant power I e (λ) (\displaystyle I_(e)(\lambda)), simplifies by taking the form

I v (λ) = K m ⋅ I e (λ) V (λ) (\displaystyle I_(v)(\lambda)=K_(m)\cdot I_(e)(\lambda)V(\lambda)), or, after going from wavelengths to frequencies, I v (ν) = K m ⋅ I e (ν) V (ν) . (\displaystyle I_(v)(\nu)=K_(m)\cdot I_(e)(\nu)V(\nu).)

From the last relation for ν 0 = 540⋅10 12 Hz follows

K m ⋅ V (ν 0) = I v (ν 0) I e (ν 0) . (\displaystyle K_(m)\cdot V(\nu _(0))=(\frac (I_(v)(\nu _(0)))(I_(e)(\nu _(0))) ).)

Given the definition of a candela, we get

K m ⋅ V (ν 0) = 683 c d ⋅ s r W (\displaystyle K_(m)\cdot V(\nu _(0))=683~\mathrm (\frac (cd\cdot sr)(W)) ), or, which is the same 683 l m W . (\displaystyle 683~\mathrm (\frac (lm)(W)) .)

Work K m ⋅ V (ν 0) (\displaystyle K_(m)\cdot V(\nu _(0))) is the value of the spectral luminous efficiency of monochromatic radiation for a frequency of 540⋅10 12 Hz. As follows from the production method, this value is 683 cd sr / W = 683 lm / W exactly.

Maximum luminous efficiency K m (\displaystyle (\boldsymbol (K))_(m))[ | ]

For determining K m (\displaystyle K_(m)) It should be noted that, as mentioned above, the frequency 540⋅10 12 Hz corresponds to a wavelength of ≈555.016 nm. Therefore, the last equality implies

K m = 683 V (555.016) l m W . (\displaystyle K_(m)=(\frac (683)(V(555(,)016)))~\mathrm (\frac (lm)(W)) .)

Normalized function V (λ) (\displaystyle V(\lambda)) given in tabular form with an interval of 1 nm, it has a maximum equal to unity at a wavelength of 555 nm. Interpolation of its values ​​for a wavelength of 555.016 nm gives a value of 0.999997. Using this value, we get

K m = 683.002 l m W . (\displaystyle K_(m)=683(,)002~\mathrm (\frac (lm)(W)) .)

In practice, with sufficient accuracy for all cases, a rounded value is used K m = 683 l m W . (\displaystyle K_(m)=683~\mathrm (\frac (lm)(W)) .)

Thus, the relationship between an arbitrary light quantity X v (\displaystyle X_(v)) and the corresponding energy quantity X e (\displaystyle X_(e)) in the SI system is expressed by the general formula

X v = 683 ∫ 380 nm 780 nm X e , λ (λ) V (λ) d λ . (\displaystyle X_(v)=683\int \limits _(380~(\text(nm)))^(780~(\text(nm)))X_(e,\lambda )(\lambda)V( \lambda)\,d\lambda .)

History and prospects[ | ]

Hefner lamp - standard "Hefner candle"

Examples [ | ]

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

For household incandescent lamps, the luminous intensity in candela is approximately equal to their power in watts.

Light intensity of various sources

Source	Power, W	Approximate light intensity, cd
Candle		1
Modern (2010) incandescent lamp	100	100
Ordinary LED	0,015..0,1	0,005..3
Super bright LED	1	25…500
Super bright LED with collimator	1	1500
Modern (2010) fluorescent lamp	22	120
The sun	3,83⋅10 26	2,8⋅10 27

Light quantities[ | ]

Information about the main light photometric quantities is given in the table.

Light photometric quantities SI

Name	Value designation	Definition	SI unit notation	Energy analogue
light energy	Q v (\displaystyle Q_(v))	K m ∫ 380 nm 780 nm Q e , λ (λ) V (λ) d λ (\displaystyle K_(m)\int _(380~(\text(nm)))^(780~(\text(nm )))Q_(e,\lambda )(\lambda)V(\lambda)\,d\lambda )	lm	Radiation energy
Light flow	Φ v (\displaystyle \Phi _(v))	d Q v d t (\displaystyle (\frac (dQ_(v))(dt)))	lm	radiation flux
The power of light	I v (\displaystyle I_(v))	d Φ v d Ω (\displaystyle (\frac (d\Phi _(v))(d\Omega )))	cd	Radiation strength (energy strength of light)
	U v (\displaystyle U_(v))	d Q v d V (\displaystyle (\frac (dQ_(v))(dV)))	lm s −3
Luminosity	M v (\displaystyle M_(v))	d Φ v d S 1 (\displaystyle (\frac (d\Phi _(v))(dS_(1))))	lm m −2	Energy luminosity
Brightness	L v (\displaystyle L_(v))	d 2 Φ v d Ω d S 1 cos ⁡ ε (\displaystyle (\frac (d^(2)\Phi _(v))(d\Omega \,dS_(1)\,\cos \varepsilon )))	cd m −2

The question of what the luminous flux is measured in began to matter to users of lighting devices only when types of lamps appeared, the brightness of which did not equal the power consumption, measured in watts.

Let's figure out how the concept of brightness is connected with the concept of illumination, as well as how you can imagine the distribution of the flow of light around the room and choose the right lighting fixture.

What is luminous flux?

The flux of light is the power of light radiation visible to the human eye; light energy emitted by a surface (luminous or reflective). The energy of the light flux is measured in lumen-seconds and corresponds to a flux of 1 lumen, emitted or perceived in 1 second. This figure describes the total flow, not taking into account the concentrating efficiency of the entire device. This estimate also includes scattered, useless light, so the same number of lumens can be found in sources of different designs.

It is necessary to distinguish between the light value and the energy value - the latter characterizes light, regardless of its property to cause visual sensations. Each photometric light quantity has an analogue that can be quantified in units of energy or power. For light energy, such an analogue is the radiation energy (radiant energy), measured in joules.

Luminous flux unit

1 lumen is the light emitted by a source with a luminous intensity of 1 candela within a solid angle of 1 steradian. A 100-watt incandescent light bulb generates approximately 1,000 lumens of light. The brighter the light source, the more lumens it emits.

In addition to lumens, there are other units of measurement that allow you to characterize light. It is possible to measure the spatial and surface flux density - this is how we find out the strength of light and illumination. Light intensity is measured in candela, illuminance is measured in lux. But it is more important for the consumer to figure out in what units the brightness of light bulbs and other lighting fixtures is indicated in the sale. Some manufacturers report the number of lumens per watt. This is how the luminous efficiency (light output) is measured: how much light a lamp gives out, spending 1 watt.

Defining Formulas

Since any light source emits it unevenly, the number of lumens does not fully characterize the lighting fixture. You can calculate the intensity of light in candela by dividing its flux, expressed in lumens, by the solid angle, measured in steradians. Using this formula, it will be possible to take into account the totality of rays coming from the source when they cross the surface of an imaginary sphere, forming a circle on it.

But the question arises, what gives in practice the number of candela that we find; it is impossible to find a suitable LED or flashlight only by the luminous intensity parameter, you also need to take into account the ratio of the scattering angle, which depends on the design of the device. When choosing lamps that shine evenly in all directions, it is important to understand whether they are suitable for the buyer's goals.

If earlier light bulbs in different rooms were selected based on the number of watts, then before buying LED lamps, you will have to calculate their total brightness in lumens, and then divide this figure by the area of ​​the room. This is how illumination is calculated, which is measured in lux: 1 lux is 1 lumen per 1 m². There are lighting standards for rooms for various purposes.

Luminous flux measurement

Before releasing products to the market, the manufacturer makes in the laboratory the definition and measurement of the characteristics of the lighting device. At home, without special equipment, this is unrealistic to do. But you can check the numbers indicated by the manufacturer using the above formulas using a compact light meter.

The difficulty of accurately measuring the parameters of light lies in the fact that it comes in all possible directions of propagation. Therefore, laboratories use spheres with an inner surface that has a high reflectivity - spherical photometers; they are also used to measure the dynamic range of cameras, i.e. photosensitivity of their matrices.

In everyday life, it makes more sense to measure such important light parameters as room illumination and pulsation coefficient. High ripple and dim lighting cause people to strain their eyes too much, which causes fatigue more quickly.

The pulsation coefficient of the light flux is an indicator that characterizes the degree of its unevenness. Permissible levels of these coefficients are regulated by SanPiN.

It is not always possible to see with the naked eye that the light bulb is flickering. Nevertheless, even a slight excess of the pulsation coefficient affects the central nervous system of a person negatively, and also reduces performance. Light that can pulsate unevenly is emitted by all screens: computer and laptop monitors, tablet and mobile phone displays, and a TV screen. Pulsation is measured with a luxmeter-pulsemeter.

What is a candela?

Another important characteristic of the light source is the candela, which is included in the 7 units of the International System of Units (SI) adopted by the General Conference on Weights and Measures. Initially, 1 candela was equal to the radiation of 1 candle, taken as a standard. Hence the name of this unit of measurement. Now it is determined by a special formula.

Candela is the intensity of light, measured exclusively in a given direction. The spread of rays on the part of the sphere outlined by a solid angle allows us to calculate a value equal to the ratio of the luminous flux to this angle. Unlike lumens, this value is used to determine the intensity of the rays. This does not take into account useless, scattered light.

A flashlight and a ceiling lamp will have a different cone of light, as the rays fall at different angles. Candelas (more precisely, millicandelas) are used to indicate the luminous intensity of sources with a directional glow: indicator LEDs, flashlights.

Lumens and Lux

In lumens, the amount of light flux is measured, this is a characteristic of its source. The number of rays that reached any surface (reflecting or absorbing) will already depend on the distance between the source and this surface.

The level of illumination is measured in lux (lx) with a special device - a luxmeter. The simplest luxmeter consists of a selenium photocell that converts light into electric current energy, and a pointer microammeter that measures this current.

The spectral sensitivity of the selenium photocell differs from the sensitivity of the human eye, so in different conditions it is necessary to use correction factors. The simplest light meters are designed to measure one type of illumination, such as daylight. Without the use of coefficients, the error can be more than 10%.

High-class luxmeters are equipped with light filters, special spherical or cylindrical nozzles (for measuring spatial illumination), fixtures for measuring brightness and checking the sensitivity of the device. Their level of error is about 1%.

Poor illumination of the premises contributes to the development of myopia, has a bad effect on performance, causes fatigue, and a decrease in mood.

The minimum illumination of the computer table surface according to SanPiN is 400 lux. School desks must have at least 500 lux illumination.

Lumen and watt

Energy-saving lamps with the same light output consume 5-6 times less electrical energy than incandescent lamps. LED - 10-12 times less. The power of the light flux no longer depends on the number of watts. But manufacturers always indicate watts, since the use of too powerful light bulbs in cartridges not designed for such a load leads to damage to electrical appliances or a short circuit.

If you arrange the most common types of light bulbs in ascending order of light output, you can get the following list:

1. Incandescent lamp - 10 lumens / watt.
2. Halogen - 20 lumens / watt.
3. Mercury - 60 lumens / watt.
4. Energy saving - 65 lumens/watt.
5. Compact fluorescent lamp - 80 lumens/watt.
6. Metal halide - 90 lumens / watt.
7. Light-emitting diode (LED) - 120 lumens / watt.

But most people are accustomed to looking at the number of watts indicated by the manufacturer when buying light bulbs. To calculate how many watts per square meter you need, you first need to decide how bright the light in the room should be. 20 watt incandescent lamps per 1 m² - such lighting is suitable for a workplace or living room; for a bedroom, 10-12 watts per 1 m² will be enough. When buying energy-saving lamps, these figures are divided by 5. It is important to take into account the height of the ceiling: if it is higher than 3 m, the total number of watts should be multiplied by 1.5.

Light flow- power of light radiation, i.e. visible radiation, estimated by the light sensation that it produces on the human eye. Light output 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, into a solid angle, one steradian (1 lm = 1 cd sr).

The total luminous flux created by an isotropic source, with a luminous intensity of one candela, is equal to 4π lumens.

There is another definition: the unit of luminous flux is lumen(lm), equal to the flux emitted by a 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- spatial density of the luminous flux, equal to the ratio of the luminous flux to the value of the solid angle in which the radiation is evenly distributed. The unit of luminous intensity is the candela.

illumination- surface density of the luminous flux incident 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 (lx), equal to the illumination created by a luminous flux of 1 lm, evenly distributed over an area of ​​1 m 2, i.e. equal to 1 lm / 1 m 2.

Brightness- 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 onto a plane perpendicular to the same direction.

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

Luminosity (lightness)- 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/m 2 .

Units of light quantities in the international system of units SI (SI)

Value name	Unit name	Expression via SI units (SI)	Unit designation
			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	lumens per square meter	cd sr / m 2	lm m 2	lm/m2
Brightness	candela per square meter	cd/m2	cd/m2	cd/m2
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	Tue	W
Light equivalent of the radiation flux	lumens per watt		lm/W	lm/W
Surface radiation flux density	watt per square meter	kg/s 3	W/m2	w/m2
Energy power of light (radiant power)	watt per steradian	kg m2/(s 3 sr)	Tue/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/m2	w/m2
Energy luminosity (radiance)	watt per square meter	kg/s 3	W/m2	w/m2

Examples:

ELECTRICAL MANUAL"
Under the general editorship. MPEI professors V.G. Gerasimova and others.
M.: MPEI Publishing House, 1998

Anyone who begins to study the characteristics of lamps and certain types of lamps is sure to come across 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 quantities in simple, understandable words. How they are interconnected, their units of measurement and how the whole thing can be measured without special instruments.

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 in the store about some kind of lumens or candela.

Today, with the rapid development of LEDs and other types of lamps, going to the store for new items 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.

In simple terms, luminous flux is the amount of light that a lamp gives.

However, do not confuse the luminous flux of individual LEDs with the luminous flux of assembled fixtures. They may differ significantly.

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

• from source power

Here is a table of this dependence for LED lamps:

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

Incandescent light bulbFluorescent Lamp Halogen HPS DRL

However, there are nuances here. LED technology is 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 forward, and have learned to shoot more lumens per watt than others.

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

On the box they will beautifully write:

• power 9W

• light output 1000lm

• analogue of incandescent lamp 100W

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 such power, you will not be close to the old light. Start swearing at LEDs and the technology of their imperfections. And the point is that it turns out to be an unscrupulous manufacturer and his product.

• from efficiency

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

It turns out that this is 10 times more efficient source than a simple light bulb. With 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 we take two lamps with the same power of blue and green, then green will seem brighter for all of us.

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 maximum to green, then the lumens are 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 1/683 W.

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

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

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

This directly affects a person's vision.

The difference between illumination and luminous flux

At the same time, many confuse the units of measurement Lumens with Lux. Remember, lux is the measurement of illuminance.

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

Also, with the help of a weak luminous flux, it is possible to create high illumination in a single area of ​​​​the surface.

1 Lux is when 1 Lumen falls on 1m2 of illuminated area.

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

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

For a typical workplace, this is 350 Lux. For a place where precise small 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 near a white wall, then there will be more suites, respectively, than from a dark one. Reflection will definitely affect the overall result.

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

Be prepared for mistakes though. But in order to make an initial analysis offhand, the phone will do just fine.

Luminous flux calculation

And how to find out the approximate light flux in lumens, without measuring instruments at all? Here you can use the values ​​of light output and their proportional dependence on the flow.

In order to quickly and efficiently perform any production task, the lighting of the specialist’s workplace must be properly organized. For this, lamps with certain photometric indicators are selected.

Lighting in the workplace is determined by various physical quantities, the main 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)

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

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

In physics, the formula is used to calculate:

F \u003d W / t, where:

• W is the energy emitted by the source, measured in watts,
• t is the device operation time in seconds.

It is also a value 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 - light intensity, measured in candela,
• w is the solid angle, calculated in steradians.

Lumen

The unit of measure for luminous flux is lumen.

In order to determine which source is more profitable to purchase, we 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 into a solid angle of 1 steradian:

1lm = 1W / 1s.

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

1 lm \u003d 1 cd 1 sr.

If the solid angle is 4π radians, and the luminous intensity is 1 cd, then in this case they talk about the total luminous flux, which is 4π lm or 4 3.14 lm.

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

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

In lighting engineering, derivative 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 slm = 10-3 lm;
• 1 µlm = 10-6 lm.

Measuring instruments

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

Photometers are visual and objective.

The principle of operation of visual instruments is based on the ability of the eye to determine the same brightness of the 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 obtaining data on the magnitude of the luminous flux, luminous intensity, as well as indicators of other photometric quantities, such as brightness, illumination distribution, etc.

Recommendations for organizing the right workplace lighting

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

Artificial 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 this lamp.

This value is indicated on the packaging of the product, so when buying, be sure to select a light bulb, guided by the information placed by the manufacturer on the box. The packaging of the luminaire 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 placed in the device.

Selection of electric lamps

Before purchasing light bulbs, you must first choose which fixtures you need to create the right workplace lighting. If the room is rectangular, then the calculation of the required number of lumens is carried out as follows: you need to multiply the indicators of the illumination norm of the object (determined according to SNiP), the area of ​​\u200b\u200bthe room and the coefficient depending on the height of the ceiling of the room.