Luminous intensity, luminous flux, illumination - 3 characteristics of lamps in simple words.

Anyone who begins to study the characteristics of lamps and individual types of lamps is sure to encounter 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 related to each other, their units of measurement and how the whole thing can be measured without special instruments.

Density, intensity and power

The light flux density is the distribution of the beam across the spectrum, which is equal to the ratio of the light of a small area to its width. Measured in watts per nanometer.

The intensity of a light source is the module with the time-averaged energy density value in a given space. Calculated from the square of the amplitude of the light wave divided by the refractive index. It characterizes the amount of average energy that is transferred by a solar wave to a time unit through an area that is perpendicular to the wave. Lines of energy are rays.

Power is the energy transferred through radiation to an object in a certain time.

Addition: The optical section, where intensity and all radiation is studied, is ray or geometric optics.

Calculation of density, intensity and power of light flux

General information

Luminous intensity is the power of the luminous flux within a certain solid angle. That is, the intensity of light does not determine all the light in space, but only the light emitted in a certain direction. Depending on the light source, the luminous intensity decreases or increases as the solid angle changes, although sometimes this value is the same for any angle if the source distributes the light evenly. Luminous intensity is a physical property of light. In this way, it differs from brightness, since in many cases, when they talk about brightness, they mean a subjective sensation, and not a physical quantity. Also, brightness does not depend on the solid angle, but is perceived in the general space. The same source with a constant luminous intensity can be perceived by people as light of different brightness, since this perception depends on environmental conditions and on the individual perception of each person. Also, the brightness of two sources with the same luminous intensity may be perceived differently, especially if one produces diffuse light and the other directed light. In this case, the directional source will appear brighter, even though the luminous intensity of both sources is the same.

Luminous intensity is considered as a unit of power, although it differs from the usual concept of power in that it depends not only on the energy emitted by the light source, but also on the wavelength of the light. The sensitivity of people to light depends on the wavelength and is expressed by the function of relative spectral luminous efficiency. The luminous intensity depends on the luminous efficiency, which reaches a maximum for light with a wavelength of 550 nanometers. This is green. The eye is less sensitive to light of longer or shorter wavelengths.

In the SI system, luminous intensity is measured in candelas

(kd).
One candela is approximately equal to the intensity of light emitted by one candle. the candle
(or international candle), is sometimes also used One candle is approximately equal to one candela.

If you measure the luminous intensity using a plane that shows the spread of light, as in the illustration, you can see that the magnitude of the luminous intensity depends on the direction towards the light source. For example, if the direction of maximum emission of an LED lamp is taken to be 0°, then the measured luminous intensity in the 180° direction will be much lower than for 0°. For diffuse sources, the luminous intensity for 0° and 180° will not be much different, and may be the same.

In the illustration, light emitted by two sources, red and yellow, covers an equal area. Yellow light is diffused, like candle light. Its strength is approximately 100 cd, regardless of direction. Red is the opposite, directional. In the direction of 0°, where the radiation is maximum, its strength is 225 cd, but this value quickly decreases with deviations from 0°. For example, the luminous intensity is 125 cd when directed at a source of 30° and only 50 cd when directed at 80°.

What is the power of light

For a person who is not familiar with the basic physical quantities that characterize the propagation of photons - light sources in the environment, the intensity of light is determined by the brightness of the light bulb. The brighter it shines, the stronger the luminous intensity is a widely held belief.

In fact, the power of light is not like that. Luminous intensity is a derivative quantity. It is calculated using a formula in which the determining factors are the luminous flux (denoted by the sign Ф) and the solid angle (denoted by the sign ω).

To make it clearer that the intensity of light does not directly depend on the power of the light bulb, let’s give an example: everyone is familiar with the design of a flashlight or spotlight. They use lamps placed in mirror condensers. The power of a flashlight bulb is usually small, rarely exceeding 35 W (halogen). If such a light bulb is used without a condenser in a dark room, then the light intensity emitted by it evenly in all directions will be small. The room will be dark and uncomfortable. To enhance the light intensity, a parabolic mirror condenser is used, which directs the light rays in the desired direction, while simultaneously limiting its spread in all directions.

The intensity of light in the beam of a flashlight (spotlight) will be greater, the narrower the solid angle. This phenomenon of condensation of the light flux in a narrow area allows you to save electrical energy and use low-power light sources to obtain the required illumination.

The luminous intensity is not indicated on the packaging of the light bulbs, since it depends on the design of the lighting device (chandelier, lampshade, sconce). With the same power of two light bulbs located in the same room, the intensity of light emanating from a lamp placed in a parabolic lampshade will be greater than that of a freely hanging lamp.

For those who do not know or have forgotten, let us remind you how light is measured. The unit of measurement is the candela (cd.). Translated from Latin - candle. It corresponds to a luminous flux of 1 lm (lumen) per illuminated surface of 1 sr. (steradian).

What is measured in lumens and lux

Lumen and Lux ​​are units for measuring the brightness of radiation and illumination of a room. These are more accurate values ​​than power, since light sources with the same indicators, but different efficiency and spectral characteristics, emit a different flux of light.

Light emitted by Lm and Lk

However, it is worth remembering that the brightness level is influenced not only by the light source, but also by 2 other factors:

• The wavelength of the emitted light - lighting with a color temperature of 4200 Kelvin (daylight lamp) is better perceived by vision than an indicator close to the yellow or red part of the spectrum.
• Direction of light propagation - narrowly focused devices allow you to concentrate light radiation in the right place, without the need to install bright lamps.

Watt, kilowatt and kilowatt-hour

The unit of measurement watt got its name in honor of the scientist James Watt, who studied electricity in the nineteenth century. It is he who is credited with the invention of the universal steam engine.

Today, any power is measured in watts, not just electrical power. For example, to measure the power of a car engine, watts are also used along with horsepower. However, most often it is not the “watt” itself that is used, but its derivative, the kilowatt (kW). By analogy with the meter and kilometer, as well as with the gram and kilogram, one kilowatt is equal to a thousand watts.

Energy is often also calculated in other units, multiples of the watt. For example, to measure high power it is convenient to use the megawatt, a unit that corresponds to a million watts. You can also use other prefixes of the international system of units, including those that correspond to tenths, hundredths, thousandths.

For example:

• deciwatt is a tenth of a watt;
• centiwatt - its hundredth part;
• A milliwatt is a thousandth of a watt.

The electric power that is consumed by ordinary household appliances such as lamps, refrigerators, and TVs is best measured in kW. If the watt and its derivative units are included in the SI system, then the kilowatt-hour is not there. KWh is a unit of measurement that is non-systemic. It was created only to keep track of the electrical energy produced or, conversely, used.

The use of kWh on the territory of the Russian Federation is regulated by GOST, which clearly indicates the name, designation and area in which it is used. A kilowatt-hour can be designated either by four Russian letters or three English ones. The Russian designation is “kWh”, and the English designation is “kW h”.

Parameter designation in SI

Since Iv is a physical quantity, it can be calculated. A special formula is used for this. But before you get to the formula, you need to understand how the desired quantity is written in the SI system. In this system, our quantity will be displayed as J (sometimes written as I), the unit of which will be the candela (cd). The unit of measurement reflects that Iv emitted by a complete emitter over a cross-sectional area of ​​1/600000 m2. will be directed in a direction perpendicular to this section. In this case, the temperature of the emitter will be close to the level at which, at a pressure of 101325 Pa, hardening of platinum will be observed.

Note! The candela can be used to define other photometric units.

Since the luminous flux in space is distributed unevenly, it is necessary to introduce such a concept as a solid angle. It is usually denoted by the symbol . Luminous intensity is used for calculations when the dimensional formula is applied. Moreover, this value is related through formulas to the luminous flux. In such a situation, the luminous flux will be the product of Iv and the solid angle to which the radiation will propagate. Luminous flux (Фv) is the product of luminous intensity and the solid angle through which the flux propagates. Ф=I .

Luminous flux formula

From this formula it follows that Fv represents the internal flux propagated within a specific solid angle (one steradian) in the presence of Iv of one candela.

Note! The steradian is understood as a solid angle that cuts out a section on the surface of a sphere that is equal to the square of the radius of the given sphere.

In this case, Iv and power can be related through light radiation. After all, Fv is also understood as a quantity that characterizes the emission power of light radiation when perceived by the average human eye, which is sensitive to radiation of a certain frequency. As a result, the following equation can be derived from the above formula:

Formula for luminous intensity

This can be clearly seen in the example of LEDs. In such sources of light radiation, its strength is usually equal to the power consumed. As a result, the higher the electricity consumption, the higher the radiation level will be. As you can see, the formula for calculating the value we need is not so complicated.

In what units is illumination measured?

Many ordinary people often ask the question - how is light measured? To assess lighting efficiency, the total number of illumination units in the SI system is calculated. These are lux and lumen.

The unit of surface illumination is defined in Lux (lux) and has the following characteristics:

• One lux is an area of ​​1 m² uniformly illuminated by a luminous flux of 1 lm.
• If the light falls at an angle, the illumination decreases.
• Illumination decreases with increasing distance from the light source.

Important! With higher lumens, the light is brighter, and with sufficient lux values, the surface is better illuminated. Is it necessary to measure the degree of illumination and its compliance with standards? Bright or dim light impairs vision and damages the retina

Lack of brightness reduces performance and mood. In the visible spectrum, the human eye is sensitive to the green frequency. When perceiving green, the eye relaxes and the nervous system calms down.

Is it necessary to measure the degree of illumination and its compliance with standards? Bright or dim light impairs vision and damages the retina. Lack of brightness reduces performance and mood. In the visible spectrum, the human eye is sensitive to the green frequency. When perceiving green, the eye relaxes and the nervous system calms down.

Green color

Illumination is measured by devices with photo sensors.

Studying the energy characteristics of light

The effect of light can be different: from thermal, which manifests itself in the heating of bodies that absorb light, to electrical, chemical and mechanical. This effect of light is made possible by the presence of energy in light, so it is very important to know about the energy characteristics of light.

The various effects of light underlie the operation of technical devices. For example, security systems for various objects operate on sensitive light receivers - photocells. Thin beams of light that literally penetrate the space around the protected object are directed at photocells (Fig. 3.7), and if one of these beams is blocked, the photocell will stop receiving light energy and will immediately “report* this - an alarm will sound.

Other technical devices are capable of responding not only to the presence of light energy, but also to its quantity. Thus, street lighting in large cities (Fig. 3.8) turns on automatically at the moment when the amount of solar light energy received decreases to a certain value. The operation of such devices is focused on the perception of light by the human eye. Therefore, the importance of considering the energy characteristics of light based on the direct perception of light by the eye—visual sensation—is obvious.

We recommend reading: Labeling capacitors - capacitor decoding table

How to use a lux meter?

You can quickly and safely find the desired measurement range for a photodetector if you act in a certain sequence:

1. Install attachments with maximum light absorption (K and T) on the photodetector, turn on the right button, which corresponds to measuring the maximum illumination - 100,000 lux. If the measuring needle does not respond, turn on the left one (up to 30,000 lux).
2. If the arrow does not move, replace the filter with a more transparent one (P) and turn it on in the same sequence: first the right button, then the left one.
3. If there is no movement, install a soft filter (M) and perform similar manipulations.
4. If in this case, when the left button is pressed, the result is less than 5 lux, remove the base attachment K and end the search.

To move the measured value away from the area of ​​overlap of the two scales (in the region of 5–20 divisions), it is recommended to start counting the measurement from 5 divisions on the inner scale, or from 20 on the outer scale. For this purpose, reference points are marked on the scales.

Remember: excessive illumination of the selenium photosensor may affect the accuracy of the measurements, so follow the given sequence of actions.

How is illumination related to luminous flux?

Illumination and luminous flux are different, although similar concepts.
Illumination is measured in lux rather than lumens. 1 lux means 1 lumen per 1 m2 of area. For clarity, you can compare force and pressure. Using a small needle and applying a minimum of force, a high specific pressure coefficient is created for a specific point. Similarly, a low beam of light can illuminate a separate area.

The interaction of light flux and illumination is easy to understand using the example of a table lamp with a luminous flux of 1000 lm. In order for the lighting to be complete, they are guided by SNiP 52.13330 standards. For the workplace, a value of 350 Lux is used, for manipulations with small parts - 500 Lux. Illumination is also affected by the distance of the light source, the color of foreign objects, and the presence of a mirror or window. That is, a table next to a white wall will receive more lux than a table next to a dark one.

Limitations on illuminance calculations

These calculations were carried out in a highly simplified form. A case of complete darkness was taken. During most of the working day the sun shines through the window, therefore, part of the illumination is provided by a natural source. It is logical to break the illumination into several parts, each intended for its own time. Much is determined by the design of the lighting fixture. For example, if the lampshade clearly introduces losses, the reflector of the flashlight significantly enhances the flow in a given direction. Source characteristics are given separately from the lamp. An obvious, often overlooked fact.

In practice, the illumination parameter is measured with a luxmeter. It is known: engineering calculations contain errors. In any industry the value is known. In radio engineering it reaches 30%. Lighting calculations are carried out approximately; the requirements of existing standards must be met exactly. Therefore, the result must be checked. A lux meter is used to show the true illumination of an area of ​​the room. The instrument readings are compared to tabulated values ​​taken from the standards.

The luminous flux indicated by the label is not constant over the area of ​​the sphere. In practice, the simplified case when the lamp is located above the object is not always encountered. You should take projections of the surface under study onto the ball and work in the chosen key.

What is "lumen"

In the middle of the twentieth century. To avoid confusion in units of measurement between different countries, the universal SI system was introduced. It is thanks to her that we have watts, amperes, meters, kilograms, etc.

According to it, the unit of measurement of luminous flux (visible electromagnetic radiation) is the lumen. In fact, these units measure the amount of light emanating from its source.

Also, to the question of what “lumen” is, you can answer that this is the name of a famous Russian rock band from Ufa. Having started its activities in 1998, it has continued to be loved by many listeners in the Russian Federation and abroad for almost twenty years.

Unit

Illumination is the luminous value that is equal to the flux of light incident on a surface to its area. It is considered directly proportional to the light source. Differs in uniform distribution on the area. It is found by dividing the candela luminous intensity by the distance to the light source and multiplied by the cosine of the angle of incidence of the sun's rays.

Note! It is measured according to the international classification system in lux, which is equal to ten photos or one lumen per square meter. Therefore, the unit of illumination measurement is lux

It is worth noting that it can be converted to candela and watt.

Basic unit of measurement lux

Candela

Candela, translated from English as candle, is a unit of measurement of the intensity of a light source according to the International Unit System. It was formed in 1979. Equal to 540⋅1012 Hz or 683 lm/W. Various light sources are measured in candelas, for example, an incandescent lamp with a candle, a super-bright LED, a fluorescent lamp and the sun. Addition: the approximate solar power in candelas is 2.8⋅10, which translates into watts of 3.83⋅1026

Candela

Lumens and Luxes

A lumen is a unit of measurement that is equal to the flux of sunlight emitted by a source, equal to a candela and a steradian. The entire light flux is measured in lumens, but the calculation does not take into account the strength of the lens with reflectors, so the resulting indicator is not a direct parameter for assessing the brightness with the efficiency of the source.

Lux is the SI measuring subunit of lumen. Unlike lumen, lux gives an estimate of the luminous flux that falls per square meter. The same gives an understanding of what luminous flux the light source has.

Note! That is, lux is a characteristic that allows you to find out the efficiency of a lamp in a specific area. To better understand their main difference, it is worth considering the figure

It clearly shows how as the height increases, the lighting expands and how the brightness decreases

To better understand their main difference, it is worth considering the figure. It clearly shows how as the height increases, the illumination expands and how the brightness decreases.

Lumen and lux as a measurement unit

Lumen and Watt

As stated above, a lumen is the full amount of light from a light source. Watt is an indicator of how much power, heat flux, sound energy and total power of electric current or radiation a device has. One watt equals 100 lumens. The translation can be done independently using special formulas or with the assistance of calculators. Often all the necessary indicators are given on the device itself.

It is worth noting that modern LEDs have the best performance. They have high brightness, harmonious spectral distribution, durability, and resistance to various types of influences. Interestingly, if we take devices with the same illumination, they will consume ten times less electrical energy than incandescent lamps.

Note! Considering the actual service life and reduced operating investment costs, the purchase of these products will be economically feasible. Converting lumens to watts

Converting lumens to watts

Multiples of units

For convenience, lumen units are disassembled into parts. So, there are kilolumens, megalumens and gigalumens. There are 1000 lumens in one kilolumen, 1000000 in a megalumen, and 1000000000 in a gigalumen. There are also other quantities with the prefixes deca, hecto, tera, peta, exa, zetta and iotta.

Submultiple units

The same approach applies to submultiple values. The basic ones are millilumens, microlumens and nanolumens, which are equal to 10 to the −3 power, 10 to the minus 6 power and 10 to the minus 9 power. There are also the prefixes deci, santi, pico, femto, atto, zepto and iokto. It is worth noting that submultiples, as well as multiples, are used only in professional settings and when performing physical tasks. In real life, illumination measures and other parameters are not used for calculations.

Lighting quantities

Light flow

Characterizes the power of visible radiation by its effect on the human eye in special units - lumens [Lm].
Luminous flux is the most important characteristic of lamps. A regular 100 W incandescent lamp has a luminous flux of 1300 Lm, and a 70 W metal halide lamp has a luminous flux of 6000 Lm. Illumination
This is the surface density of the luminous flux incident on an area of ​​a given size.
The unit of illumination is lux [Lx]. One of the most important values ​​in lighting standards. Most often, horizontal illumination is normalized (in the horizontal plane). The range of illumination levels with artificial lighting is from 1 to 20 Lux outdoors and from 20 to 5000 Lux indoors. Under natural conditions, illumination E = 0.2 Lux on a full moon, 5000 - 10,000 Lux during the day with overcast clouds and up to 100,000 Lux on a clear sunny day. Luminous intensity
This is the spatial density of the luminous flux, limited by the solid angle.
The unit of measurement of luminous intensity - candela [cd] - is reproduced by the standard and is included in the International System of Basic Units (SI). The distribution of luminous intensity in space (luminous intensity curve, LIC) is one of the most important characteristics of lighting devices necessary for lighting calculations. The KSS of lamps is usually given in polar coordinates for a conventional lamp with a luminous flux of 1000 lm, i.e. in cd/kLm. Brightness
For matte (diffuse or equal-brightness) surfaces, this value is proportional to the surface density of the light flux reflected or emitted by this surface.
In a more general form, it is equal to the ratio of the light intensity in the direction of the observation point to the area of ​​the luminous surface (projection) visible from this point. The brightness unit is cd/m2. Brightness is directly related to the level of visual sensation, and the distribution of brightness in the field of view (for example, in an interior) characterizes the quality of lighting. In complete darkness, a person reacts to a brightness of one millionth of a cd/m2. A solid luminous ceiling with a brightness of more than 500 cd/m2 has an uncomfortable effect. The brightness of the sun is about 1,000,000,000 cd/m2, and that of a fluorescent lamp is 5-11 thousand cd/m2. Reflection [ρ] and transmittance [τ] coefficients
are defined as the ratio of the luminous flux reflected [ρ] or transmitted [τ] by the material to the incident luminous flux.
Reflection coefficients of some finishing materials: - white paint (0.7 - 0.8) - light wallpaper (0.5 - 0.7) - white marble - 0.45 - red brick - 0.3 - dark wood (0. 1 - 0.25) - asphalt - 0.07 When rooms are decorated with light (especially when the size is small relative to the height), the illumination levels increase very noticeably. The reflectance coefficient of the background against which the object is viewed is one of the indicators characterizing the conditions of visual work in the workplace. According to Russian standards, the background is considered light with a reflectance coefficient of more than 0.4, medium - from 0.2 to 0.4, and dark - less than 0.2. As the background reflectance increases, the visibility of the object improves. Luminous efficiency
This is the main characteristic of the energy efficiency of lamps and it is equal to the ratio of the luminous flux of the lamp to its power.
The use of lamps with high luminous efficiency is the main way to save energy in lighting installations. For example, by replacing incandescent lamps, the luminous efficiency of which is 7-22 lm/W, with compact fluorescent lamps (50-90 lm/W), you can reduce energy consumption by an average of 5-6 times without reducing the level of illumination. Indicators of glare and discomfort
These indicators characterize the direct glare of light sources or lamps.
Based on the glare indicator, one can judge the degree of deterioration in visibility when exposed to glare light sources. For example, with a value of 100, visibility is reduced by 10%. According to Russian standards, for precision production work, the value of the glare index should be no higher than 20. The discomfort index (M) characterizes the degree of discomfort or tension in the presence of sources of increased brightness in the field of view. Cylindrical illumination [Ec]
Characterizes the saturation of a room with light and is defined (in lux) as the average vertical illumination created at a given observation point.
In Russia, this value is standardized in such premises as halls, front vestibules, auditoriums, exhibitions, reading and trading rooms, meeting and reception rooms, etc. Increased light saturation is created at Ec levels of at least 100 lux. Color and chromaticity
The concept of color is defined as the property of visible radiation to cause a visual sensation of color (hue + saturation) and brightness of objects.
Hue (red, orange, etc.) is characterized by the wavelength of visible radiation, and saturation is characterized by the purity of color associated with the degree of approximation to a spectrally pure color from the white point. For example, low-saturated color tones are obtained by greatly diluting the dye with white paint. The color of the same object can vary greatly depending on the spectral composition of the lighting. Color temperature [Tc]
A very important characteristic of light sources that determines the color of the lamps and the color tone (warm, neutral or cool) of the space illuminated by these lamps.
It is approximately equal to the temperature of a heated body of the same color as a given light source. Expressed in the Kelvin temperature scale: T = (degrees Celsius +273) K. Tc values ​​of some sources: - candle flame - 1900 K; — incandescent lamps – 2500-3000 K; — fluorescent lamps – 2700-6500 K; — Sun – 5000-6000 K; – cloudy sky – 6000-7000 K; - clear sky - 10000-20000 K; Color rendering index [Ra]
One of the main color characteristics of the quality of discharge lamps.
Characterizes the degree of color reproduction of various materials when illuminated by a lamp when compared with a reference light source. The highest value is Ra=100. High-pressure sodium lamps with the worst color rendering have Ra=25. According to German standards, very good color rendering (grade 1) corresponds to Ra = 80 or more, good (grade 2) - from 60 to 79, satisfactory (grade 3) - from 40 to 59 and insufficient (grade 4) - from 20 to 39 Illumination pulsation coefficient [Kp]
Characterizes the relative depth of illumination pulsation (in%) at a given point in the room when the lamps are powered from an alternating current network . Uncontrolled pulsation of illumination leads to an increased risk of injury when working with moving and, in particular, rotating objects, as well as to visual fatigue. In Russian standards, for most visual work, the Kp value is set to no more than 20.

Illumination concept

The luminous flux is measured under special laboratory conditions and cannot be determined spontaneously. Therefore, SNiP takes into account the amount of illumination, which, unlike the luminous flux, everyone can measure independently. It is a measure of the ratio of luminous flux, measured in lumens, to the surface area on which photons fall. The angle of incidence should be 90°. The unit of illumination is lux.

Surface illuminance unit

The dependence of a person’s psychological and physical states on light has long been established. If in low light the brain processes are depressed, then in bright light they are stimulated. But in any case, the retina and the body’s resources wear out. When designing lighting devices, a safety factor (SF) is determined, which should take into account the likely decline in illumination of the installation. For artificial light, the indicator provides for a decrease in brightness due to wear and tear of the optical components of the device and their natural contamination. The coefficient of natural illumination decreases due to changes in the reflective properties of surrounding objects.

Illumination measurements are carried out at workplaces along with determination of the level of pollution, sound vibrations, electromagnetic radiation, and in some industries, gamma radiation

The importance of knowing these parameters can hardly be overestimated when creating optimal working conditions, and all of them comply with sanitary rules and regulations. For example, the illumination should be:

• in the office - 300 lux;
• in the office for constant work with a computer - 500 lux;
• for technical and design bureaus - 750 lux.

Standards for indoor lighting for use (SNiP)

The standard of illumination must be taken into account when arranging administrative, educational, leisure institutions, household enterprises, shopping facilities, residential buildings, local areas, hotels, enterprises, as well as pedestrian and vehicular zones in cities and villages.

When selecting a lighting system, they are guided by documents SNiP 23-05-95 from 1995 and its updated version SP 52.13330 from 2011 for natural and artificial light sources.

Lighting in the office

Stress resistance, concentration, and mental activity of personnel will depend on the level of lighting. You can familiarize yourself with the regulatory requirements in the table.

Light intensity in production

To determine the indicator, visual load is taken into account.

Lighting in warehouses

The intensity of the light sources depends on the type of storage and type of lamp.

Lighting parameters in residential buildings and leisure centers

For an office, billiard room, library, the standard table height is 0.8 m from the floor line.

The specified standards are taken into account when arranging electrical wiring and installing lighting fixtures.

Illumination and brightness

Illumination is the magnitude of light; it determines the amount of light that falls on a particular surface area of ​​the body. It depends on the wavelength of light, because the human eye perceives the brightness of different wavelengths of light differently, in other words, different colors.

Illuminance is calculated for different wavelengths separately. People perceive the brightest colors as:

• green - light with a wavelength of 550 nanometers;
• yellow orange. They are located next to it on the spectrum.

The light coming from red, blue and violet colors has a short or long wavelength, so they are perceived as darker. The concept of illumination is often correlated with the concept of brightness.

When lighting an area with the same lamp, a large area will be less illuminated than a small one.

Difference between brightness and illuminance

means a characteristic of luminous bodies

• structural features of human eyes;
• amount of light in the room.

The less light there is in the environment, the brighter the light source appears to us. You should distinguish between brightness and illumination and remember the following:

• brightness is the light that is reflected from the surface of a luminous object;
• Illuminance is the light that falls on the illuminated surface.

In astronomy, brightness includes two concepts, where stars emit and planets reflect. In this science, stellar brightness is measured on a photometric scale, with a greater brightness of a star being correlated with a smaller value. The brightest stars have a negative magnitude.

The difference between illumination and luminous flux

Let's count lighting together!

When a light flux of 1 lm falls on an illuminated area of ​​1 m², an illumination of 1 lux is obtained. Illumination is designated by the letter E and measured in lux (lx). It can be calculated using the formula:

E = Ф/S, where:

• F – light flux, lm;
• S – surface area, mm2.

The difference between these two physical quantities is understood as follows: 1 lux = 1 lm/m² of illuminated surface.

What is "luminous flux"

Physicists use luminous flux to denote the power of light radiation visible to the eyes (its electromagnetic energy) that passes through a body or surface in a certain time. To a person who does not have a certain level of knowledge in physics, this concept means nothing. In everyday life, the light beam determines the properties and quality of lighting depending on the type of lamp. For industrial, public and office buildings, the values ​​are regulated; in a private house, the indicators can be used when calculating the lighting system.

Physicists know that light energy is electromagnetic waves; human eyes see them only in a certain range of wavelengths.

The quality of the light beam depends on:

• source power;
• chemical composition of the lamp;
• features of the bulb (lens);
• light output level.

In everyday life, it is important to know that the luminous flux is directly proportional to the power of the lamp. Another definition of the concept of “luminous flux” is the total volume of light, independent of the optical system installed around the lamp

For example, a lamp with an incandescent filament emits 415 lumens, regardless of the design and material of the lampshade

Another definition of the concept of “luminous flux” is the total volume of light, independent of the optical system installed around the lamp. For example, a lamp with an incandescent filament emits 415 lumens, regardless of the design and material of the lampshade.

Light intensity

The unit of light intensity is measured when arranging lighting in a room or when preparing the camera for shooting. Experienced photographers and professional lighting engineers use digital exposure meters, but you can also make a simple device with a similar operating principle with your own hands.

Many devices are designed for a separate type of lighting. For example, by measuring the glow of sodium lamps, you will achieve a more accurate result than by performing calculations on an incandescent lamp.

You can install an application on your smartphone that will determine the light intensity. No matter how good your phone and the selected application are, the results will be distorted and inaccurate, so it is better to use a specialized device.

Most devices measure illuminance in lux, as this is a common unit, but some are set to display footcandles.

If you are not comfortable with one of these measurement methods, you can convert lux to candelas and vice versa on this resource:

What is Lumen and Lux

Any light source can be characterized by its radiation intensity. In the international system it is measured in candelas (LD). The derivative of candela is a quantity characterizing the luminous flux - lumen, abbreviated as Lm. That is, Lumen is a unit of measurement of luminous flux.

1 - 2 magnitudes

A certain number of light rays, measured in Lm, fall on a surface with a certain area, causing it to become illuminated. Lux is a unit of illumination measurement that is closely related to lumen.

The difference between Watt is that it denotes the amount of energy consumed. This value does not indicate the number of rays emitted, but how much energy will be spent when the LED is operating. For example, a 200 W light bulb uses more electricity than a 100 W light bulb.

Light bulb power in Watt

Note! Modern lamps and products with LEDs indicate the amount of light emitted in lumens, or the luminous efficiency value in Lm per W. The product packaging must contain information about how much light it provides.

You may notice that incandescent lamps provide 12 Lumens per 1 Watt, while LED devices provide up to 90 Lumens per Watt. Fluorescent lamps have a maximum illumination with energy consumption of 60 Lm per W

The product packaging must contain information about how much light it provides. You may notice that incandescent lamps provide 12 Lumens per 1 Watt, while LED devices provide up to 90 Lumens per Watt. Fluorescent lamps have a maximum illumination with energy consumption of 60 Lm per W.

Packaging of light bulbs

Important! Using this approach, it is not always possible to obtain the correct results, because even products of the same type with equivalent power may have different ratios. Below is a table showing the exact values ​​for converting watts to lumens for light bulbs:

Below is a table showing the exact values ​​for converting watts to lumens for light bulbs:

It follows from the table that an LED lamp with a luminous flux of 600 Lm is not equivalent to a 60 W incandescent lamp, and 1000 Lm is not equivalent to a 100 W lighting fixture.

How and in what way is it measured?

The unit of luminous flux is designated 1 lumen (lm or lm), with 1 lumen equating to a luminous flux of 1 candela emitted in 1 steradian. Lighting brightness is calculated in cd/m².

Intensity is never shown as a straight line on a graph. It extends in different directions and has a solid angle. The vertex of such an angle is located at the center of the sphere. The dimensions of the illumination intensity angle are expressed in steradians.

Unlike the usual flat angle from geometry, this angle is volumetric and will be graphically conveyed in the form of a cone. Although experts consider this comparison not entirely correct.

A 100 V incandescent lamp has a luminous flux of 1380 lm, and a 40 V LB fluorescent lamp has a luminous flux of 2800 lm.

Interesting Facts:

1. The brightness of fluorescent lamps ranges from 5000 to 15000 cd/m².
2. The brightness of the sun's surface has a value of 2000000000 cd/m².

Knowing what kind of flow a lighting device creates is necessary in order to properly organize the lighting in the room. But often manufacturers do not indicate this parameter on the packaging of even incandescent lamps. The strength of the flux can be correlated with the power of the lighting fixture. There are special tables where this dependence can be traced. The data in it is obtained by measurements.

The most intense light flux is created by diode lamps at relatively low power. Thus, a lamp with a power of 16 W creates a flux of 1400 lm. In practice, this will mean that these illuminators will shine brighter.

Testo lux meters

One of the modern illumination meters, the most popular in Russia, is the digital lux meter Testo 540 (Germany). The device is made in one volume, the photocell is integrated with the body, which increases ease of use: there is no connecting wire that can get caught on something, measurements can be made with one hand.

The shape and dimensions of the device resemble a cell phone. The same display is used to indicate the readings, and the keyboard contains only 3 buttons: power on, selection of the measurement system (SI or American - foot-candle) and saving the results. Measuring range: 0 – 100,000 lux or 0 – 93,000 fc.

The device is ideally suited for use in everyday life. With its help, you can measure the lighting level in living rooms, schools, kindergartens, greenhouses, potato storage rooms, and so on. Operating the device is extremely simple: press the power button, select the system (triangle) and that’s it. The result will appear almost instantly. To save the measurement result, press the “mode” button.

The Testo 545 digital device belongs to the class of professional devices for measuring environmental illumination. The light receiver is made separately from the electronic unit and is connected to it by a conductor. Differs from its younger brother in greater functionality:

• memory for storing up to 3000 measurement results;
• storing 99 measurement locations in memory;
• connection to a personal computer;
• constructing a three-dimensional graph of the amount of illumination within the room;
• printing data on a printer.

This device is used in the process of measuring the illumination of buildings, structures, as well as streets, roads and other public places. The price of the Testo 540 lux meter is comparable to the price of the Yu-116 device (about 10 thousand), and Testo 545 is sold for 35 thousand rubles.

A lux meter is one of the most accessible and at the same time effective instruments for measuring the illumination parameters of an object. Its use provides comfortable conditions for a person, both in a work environment and in everyday life. We hope that this article will help you navigate when choosing a device with the necessary capabilities at an affordable price.

Comparison of incandescent and LED lamps

The LED lamp, which is part of the lighting fixtures, is more complex and more expensive than an incandescent lamp. It consists of the following components:

• module with planar LEDs;
• radiator;
• frosted flask;
• inverter

Such a lamp has a light flux F, which is measured in lumens, at the same power, 10-12 times higher than that of an incandescent light bulb.

The light output of a lamp with a spiral is in the range of 8-10 Lm/W, while the LED lamp keeps this parameter in the range of 90-110 Lm/W.

Traditional shapes and aesthetic appearance allow the LED lamp to be used either as part of any lamp or separately. Knowing the required values ​​of E and calculating or measuring the desired value of F, you can get significant savings in energy costs. At the same F, an LED light bulb consumes less energy.

By correctly using units of measurement, such as lumen, lux, Lm/W, candela, when determining the parameters of the light spectrum, you can independently select lighting devices. The use of modern LED technologies not only helps to save budget funds, but also creates comfortable conditions for living and working.

Residential lighting standards

What is a lumen in apartment lighting, and what should you pay attention to when choosing lamps? A 100-lumen light bulb installed under the ceiling will not provide the same illumination E for the table and floor surfaces. They are located at different distances from it

Main! Before choosing sources of light radiation and their design, it is necessary to remember that illumination can be not only natural, but also artificial. The latter is not only general, but also local.

The use of additional devices: table lamps, bedside lamps, reading lamps, LED backlights will help organize light that is comfortable enough for living. There are standards for the value of E, which can be clarified in various tables developed in accordance with SNiP 23-05-95 “Natural and artificial lighting”.

Typical luminous flux value for various light sources

Typical luminous flux values ​​for light sources depend on their design. The table allows you to visualize how different the luminous flux they generate can be:

TABLE 1

Luminous flux of incandescent lamps generated by various light sources

TABLE 2

Luminous flux table for fluorescent lamps

Comparison of light from different sources

Most often, light sources used in everyday life are subject to comparison:

• incandescent lamps;
• halogen lamps;
• fluorescent lamps;
• light-emitting diode (LED) lamps.

The maximum permissible incandescent lamp in everyday life usually does not exceed 200 W. More powerful lamps become very hot and are a fire hazard. It should be taken into account that the luminous efficiency of various types of lamps is not characterized by power alone.

The luminous flux of a 100 W incandescent lamp is sufficient to create comfortable lighting in a room with an area of ​​9-12 m2.

The same luminous flux of fluorescent lamps is provided at a power of 40 W.

LED light source is the most economical in terms of energy consumption. The 7 W LED block replaces a hundred-watt light bulb in terms of light output.

Work surface lighting

The requirements for lighting work surfaces are as follows:

• SNiP 23-05-95;
• SanPin 2.2.1/2.1.1.1278-03

The work table should have an illumination of 300 lux, the workplace for precision work should have 500 lux, and 150 lux is enough to illuminate the work surfaces in the kitchen.

Examples [ | ]

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

For household incandescent lamps, the luminous intensity in candelas is approximately equal to their wattage.

Light intensity of various sources

Other lighting characteristics

The characteristics of light were partially discussed in previous sections. For better remembering, let's repeat.

What is candela?

Candela is a unit of luminous intensity (cd). One of the 7 basic units of the SI system. Equals 1 lumen multiplied by 1 watt to the minus first power.

lm x W-1

Lumens and Luxes

As already noted, similar-sounding units are used to characterize different concepts:

• illumination is measured in lux (lx);
• luminous flux is measured in lumens (lm).

Lumen and Watt

Lumen, as a unit of measurement of luminous flux, is not identical to watt, a unit of measurement of power. Despite the fact that in everyday life people often equate the power of a light bulb, expressed in watts, with luminous efficiency , this should not be done. An illustrative example: the equality of the luminous flux emitted by a 100 W incandescent lamp and a 7 W LED lamp.

Main conclusions

It is not necessary for the average consumer to know the exact definitions of the concepts used in the calculations of lighting systems. If you just need to replace a burnt-out light bulb, just remember that a watt is not a lumen at all. The first determines power, the second determines illumination. When switching to another type of light source, it is quite possible to do without calculations if you find a table on the Internet.

Now, when buying lamps, you need to focus not on watts, but on lumens, and remember that this indicator largely depends on the design of the source. For example, a fluorescent lamp is quite capable of providing 2500-2500 lumens, and the indicator depends on the characteristics of the bulb. Most often, problems are caused by LED sources if low-quality products are purchased.

When choosing, it is also necessary to take into account the decrease in the brightness of the glow during operation. Indicators vary from source to source. An incandescent lamp can lose up to 15% of the flux, a fluorescent lamp can lose up to 30%, and an LED lamp can lose up to 5-10%. When purchasing, be sure to take into account the required stock.

If you are carrying out independent repairs that involve changing the lighting system, it is better to order a lighting calculation. Any mistake may result in additional costs. It is impossible to independently take into account all the nuances without special software. If you choose the right specialist, he will help you choose the type of lamps that will save on electricity. After installation there will be no unpleasant surprise in the form of insufficient light levels.

Previous Lighting in an apartmentHow to correctly calculate lighting based on the area of ​​a room Next Lighting in an apartmentHow to correctly measure the level of illumination in a room and what it should be

Watts and Lumens

Until recently, when choosing light bulbs, we focused on power, or the number of watts. The larger it is, the higher the lighting was better. Nowadays the designation of lighting quality is made in lumens.

But Watt cannot be simply converted to Lumen, since the first designation is power, and the second is the volume of light rays from sources. For transformation, you need to know the light output (lm/W), as well as the type of lamp, the efficiency of the reflector, losses in the presence of a diffuser, and the percentage of luminous flux leakage.

Instead of lengthy calculations, you should focus on the summary table.

If you want to save money, replace a 1000 W incandescent light bulb with a fluorescent (25-30 W) or LED (12-15 W) device.

How and in what quantity is luminous flux measured?

Luminous value - DP is measured in lumens. One lumen is equivalent to the DP of an isotropic light source with an intensity of 1 candela and an angle of 1 steradian.

In production, special instruments are used for measurements. This method allows you to accurately determine the SP:

• A photometer is a device with a camera sphere. The reflectance of the interior is 1. The measurement is carried out by placing a light bulb in the center of the chamber and establishing a diffuse light beam.
• A goniometer is a photometric device with a built-in lux meter that can move around a sphere. During the illuminance integration process, the value in lumens is displayed.

Photometer

Goniometer

The lux meter is calibrated in absolute terms: 1 lm/m2 equals 1 lux.

An ordinary person, when choosing a lamp or lamp, does not need to delve into the exact measurement system. When replacing an incandescent device with a halogen one, it is worth remembering that watts are not lumens. The first are used to determine power, the second - from illumination, and during operation, a standard lamp loses 15% of its brightness, a fluorescent lamp - 30%, an LED - from 5 to 10%.