It is difficult to meet a person who does not understand the measures of length, area, volume, and weight. It is not difficult to calculate time or determine temperature. But if you ask someone about photometric quantities, then in most cases you cannot expect a clear answer. Meanwhile, we live in constant contact with lighting, natural or artificial. This means that we must learn to evaluate it in some way.

Of course, such an assessment is always made by everyone, but most often - purely at the level of subjective perception: is there enough light or not. However, such a “gradation” is precisely subjective and can produce significant errors. The consequences of such incorrect assessments cannot be underestimated - both insufficient lighting and its excess negatively affect both a person’s visual organs and his psycho-emotional state.

Meanwhile, there is a special value - illumination, the value of which is regulated by legislative acts in the field of construction and sanitation. That is, illumination is precisely the quality criterion that allows you to correctly evaluate the organization of a room lighting system. In this article we will talk about this parameter and other photometric quantities associated with it, and see how this can be used in a practical application.

Due to ingrained habit, many continue to believe that the assessment of room illumination can be done in energy units - watts. This misconception is easily explained - we are left with this persistent stereotype as a legacy from the times of complete dominance of incandescent lamps.

Incandescent lamps were produced with different power consumption - 15, 25, 40, 60, 75, 100, 150 and more watts. And every owner of a house or apartment knew from his own experience that for normal lighting in the living room, for example, he must screw three 60-watt bulbs into a chandelier, a “forty” will be enough for a table lamp, a hundred-watt one for the kitchen, etc.

By the way, a clear legacy of this is still the practice used by lamp manufacturers - to indicate on their packaging, in addition to power consumption, luminous efficiency expressed in the equivalent power of old incandescent lamps.

So let's remember the first thing - neither the luminous flux emitted by a lamp nor the surface illumination resulting from it is measured in watts. The watts indicated on the body of the device are the amount of electricity consumed by the lamp, which, through certain physical transformations, is converted into visible light.

Some people of the older generation are generally confident that the light output lighting fixture measured in candles. By the way, this is not so far from the truth, and why will become clear below. But again, this is not illumination at all.

So it makes sense to consider the main photometric quantities in order, from the light source to the illuminated surface. Let’s make a reservation right away – this topic is quite difficult for an unprepared person to understand. Therefore, we will try to simplify the presentation as much as possible and will not overload it with cumbersome formulas. So that there is simply a general understanding of the issue.

Light flow

Light, as is known, has a wave nature. In a certain range of wavelengths, electromagnetic radiation is perceived by the human visual organs, that is, it becomes visible. The approximate boundaries of this range are from 400÷450 nm (red part of the spectrum) to 630÷650 (violet region).

Electromagnetic waves are a carrier of energy - it is the energy of the Sun that provides life on Earth. But let's digress from astronomical categories and return to ordinary light sources.

So, since a source emits light, this means radiation and transfer of a certain energy. The amount of this radiant energy (We) transferred per unit time is called radiant flux (Fe). And it is measured in watts.

However, we are talking about lighting, that is, the perception of color by human vision. And estimating the amount of energy “by eye” means immediately introducing a large error. For example, two sources with equal radiation power, but with different colors glows will also be perceived by the eye differently.

To unify this parameter, a special physical quantity was introduced - luminous flux (F). This is also an indicator of the power of the radiant flux, but only that part of it that is perceived by the average healthy human eye.

Luminous flux can also be measured in watts (this is rather an energy indicator), or in lumens (light indicator). In practice, lumens are usually used.

For the exact value of one lumen, radiation from the central, green part of the visible spectrum, with a length of 555 nm, was taken as a standard.

So, it is accepted that a radiant flux with a wavelength of 555 nm and a value of 1 watt corresponds to 683 lumens. Why such a strange coefficient? It’s just that the final approval of this unit in the SI system took place in 1979, and the first experiments in photometry with the introduction of the indicator luminous flux began to be produced long before that. At that time, when electric lighting did not yet exist, and an ordinary candle served as a more or less stable, “reference” light source. And the current ratio of energy watt and light lumen was recalculated over time and passed down to the present day.

Let us remind you once again that the watts mentioned above, which can also be used to measure the luminous flux, have nothing to do with those indicated on the lamp packaging. It shows the consumption of the lamp, that is, the amount of energy that it will “take” from the network. We should be more concerned about its energetic light output - how much visible radiant energy it will “give out”. So, when choosing a lamp, it would be much more correct to pay attention not to ephemeral comparative analogies in watts, but to the clearly indicated value of the luminous flux in lumens.

Luminous output

This is a very interesting quantity in practical terms, since it essentially characterizes the efficiency of the light source. It is important to choose a lamp not based on its electrical power consumption, but on how this power is used when converted into light energy.

So, the luminous output value shows how much luminous flux is produced by the lamp when converting one watt of expended energy. It is clear that it is measured in lumens per watt (lm/W).

The conversion of one type of energy into another is carried out in different ways. For example, in conventional incandescent lamps the resistive principle is used - the glow is caused by a red-hot coil with high electrical resistance. It is clear that this is accompanied by huge heat losses. More efficient are modern lighting devices based on the principles of glow of semiconductor matrices when current is passed or specially selected gas mixtures are ionized. Here, significantly less energy is wasted on unnecessary heating.

It was already mentioned above that the peak of normal perception of light by the human eye occurs at a wavelength of 555 nm. And in ideal conditions, with full transformation electrical energy in a monochromatic light flux of the specified wavelength, that is, with absolutely no losses, it is theoretically possible to achieve a light output of 683 lm/W. This is called an ideal light source, which, alas, does not exist in nature.

The table below shows comparative characteristics for the most commonly used lamps in everyday life - incandescent, fluorescent and LED. It is clearly visible how more economical the use of modern light sources becomes, that is, how the luminous efficiency increases.

(The values ​​in the table are approximate. In any category of lamps there may be deviations in one direction or another - this depends on the quality of the particular model. But the table presents the general picture quite clearly).

Luminous flux, Lm	Incandescent lamps		Fluorescent lamps		LED bulbs
	Consumed Power, W	Luminous output lm/W	Consumed Power, W	Luminous output lm/W	Consumed Power, W	Luminous output lm/W
250	20	12.5	5÷7	41.7	2÷3	100
400	40	10	10÷13	36.4	4÷5	88.9
700	60	11.7	15÷16	45.2	6÷10	87.5
900	75	12	18÷20	47.4	10÷12	81.8
1200	100	12	25÷30	43.6	12÷15	88.9
1800	150	12	40÷50	40	18÷20	94.7
2500	200	12.5	60÷80	38.5	25÷30	90.9

The specific luminous efficiency value is not always, but is still indicated by some lamp manufacturers on their packaging. This may be the inscription “light output” or “Lighting effect”. If not, then it’s easy to determine it yourself by dividing the nameplate luminous flux by the specified power consumption.

It is quite obvious that of all the lamps used in living conditions, have the best light output indicators LED devices– for them this figure reaches 100 lm/W, and may even be slightly higher. But progress does not stand still, and the developers announce an imminent release serial production lamps with a luminous efficiency of about 200 lm/W. But the ideal source is still oh so far away...

By the way, scientists were able to estimate the luminous efficiency of the Sun, and it is not so high: approximately 93 lm/W.

About the luminous efficiency of light sources various types This is also explained in the video below:

Video: What is luminous efficiency, and what is the practical application of this parameter?

The power of light

In physics there is the concept of a point source of light - it propagates radiation exactly the same in all directions. In practice, if this happens, it is extremely rare, and even then - with some simplification of concepts. In fact, the light flux in different directions is uneven. And in order to estimate, let’s say, its spatial density, they operate with the magnitude of the light intensity. And to understand what it is, you will also have to remember the concept of a solid angle.

Let's start with geometry. So, a solid angle is a part of space that unites all rays emanating from one point and intersecting a certain surface (it is called a subtending surface). In photometry, of course, this is an illuminated surface. This angle is measured in special quantities - steradians (sr), and is usually indicated in formulas by the symbol Ω .

The magnitude of the solid angle is the ratio of the area of ​​the subtending surface to the radius of the sphere.

Ω = S/R²

That is, if we take, for example, a sphere with a radius of one meter, then a solid angle of one steradian will “cut” a spot on its surface with an area of ​​one square meter.

Why know this? The fact is that the concept of luminous intensity is directly related to the solid angle. Specifically, a luminous flux of one lumen, propagating in a space limited by a solid angle of one steradian, has a luminous intensity of one candela. Mathematically, this relationship looks like this:

I = Ф/ Ω

And if we talk about the energy intensity of light equal to one candela, then this is 1/683 W/sr.

By the way, the candela is one of the seven basic quantities of the SI system.

Candela literally means candle in Latin. This is exactly that “relic of the past” that was already mentioned above, but it very clearly shows the entire interconnection of quantities.

Let's explain in the figure:

So, there is a point source of light - a candle. Its burning wick emits light with a force of one candela (item 1).

In a space limited by a solid angle equal to one steradian (item 2), a luminous flux (item 3) equal to one lumen will propagate. At a certain distance from the source (radius of the sphere - position 4), this flow illuminates the surface of a certain area (position 5). Looking ahead, we will immediately say that if the area is equal to one square meter, then under such conditions in this “light spot” an illumination equal to one lux (lx) is provided.

If we return to the candle as a reference light source, then it is easy to calculate its total luminous flux. A complete sphere has a solid angle of 4π, that is, with slight rounding, it is equal to 12.56 steradians. This means that a candle emitting light of one candela in all directions produces a total luminous flux of 12.56 lumens.

It is interesting that not so long ago the emissivity of light sources was assessed “in candles”. For example, they said that you need a “light bulb for sixty candles.” Sellers and buyers understood each other perfectly - a 60 W incandescent light bulb was purchased, although, in fact, these values ​​​​are in no way related to each other in this case, from a physics point of view, are not related. And what’s funny is that it was close to the truth.

Let's see - 60 candles of 12.56 lumens will give a total of 753.6 lumens. Let's look at the table above - an incandescent lamp with a consumption of 60 watts has a luminous flux of approximately 700 lumens. Very close!

But, we repeat, a correct assessment of light sources should still be carried out in lumens.

Light brightness

Another parameter worth considering is the brightness of the light source. The fact is that there is practically no need to deal with point sources. That is, most sources have some specific emitting surface. And with an equal luminous flux, but a different area of ​​light emission, it will be perceived differently by vision.

That is, in essence, brightness is the strength of light emitted from a certain unit area of ​​the visible surface of a light source.

It is clear that the unit of brightness will be candela per square meter.

This is an important value, since the organs of vision, when looking at a light source, react, rather, not to the intensity of light as such, but rather to brightness. When its value is large (over 160 thousand candelas per square meter), the light can cause eye irritation, pain, and tearfulness. That's why lighting manufacturers produce lamps with frosted bulbs. With virtually no loss of luminous flux, the radiation does not come specifically from an incandescent filament or LED with their small areas, but from a much larger surface area of ​​the bulb. This glow is much safer for the retina of the eye and is perceived much more comfortably by vision.

Surface illumination

Finally, we got to the lighting. This value can be considered the most applied, since it is the illumination of a particular area that is assessed general work lighting fixtures.

Figuratively speaking, illumination (E) is the surface density of the luminous flux (F) distributed over a particular area (S). If we approach it with some simplification, then this can be expressed by the following formula:

As we saw above, one lumen of luminous flux on an area of ​​one square meter creates an illumination equal to one lux (lx).

Illumination depends on a number of factors, even if you do not take into account the own characteristics of the light source.

• Firstly, the further the source is located from the illuminated surface, the larger the area of ​​the “light spot” (remember the solid angle cone). That is, the luminous flux is distributed over larger area. Moreover, as we remember, this dependence is quadratic. That is, when the distance changes by half, the illumination will decrease by four times, by three times by nine times, etc.

If we consider a point source, we can apply Kepler’s formula:

We will not repeat the meaning of the quantities included in the formula - they are given above.

• Secondly, the Kepler formula shown above is valid only for a surface perpendicular to the direction of the light flux. In reality, of course, this does not happen often. That is, in the case when the illuminated plane is located at some angle α to the direction of the flow, corrections have to be made for this:

E = (I / r²) × cos α.

Remember - when you need to illuminate a surface as brightly as possible, you point the flashlight perpendicular to it. But if you place it at an angle, the illumination will drop sharply, since the light seems to be “smeared” across the surface.

• Thirdly, the illumination of a particular area also depends on its, so to speak, surroundings. The fact is that most surfaces do not absorb all the light that hits them, but largely reflect it. And thus they themselves become original sources of light.

Let's remember what was said in the section about the brightness of the glow. Yes, indeed, the brightness of such illuminated areas is not particularly high. But the radiation comes from a decent area, and as a result a very significant luminous flux is created.

And the brightness of such an illuminated surface depends both on its illumination and on its diffuse reflectivity, which has a separate name - albedo. The higher the albedo, the brighter the glow. And since it’s brighter, the “secondary” color flow is more studied.

Some illustrative examples reflected light. A sheet of white paper with illumination of only 50 lux will have a brightness of 15 cd/m². The glow of the full moon (and this, as we know, is sunlight reflected from its surface) is characterized by a brightness of 2500 cd/m². And the surface of pure white snow on a sunny day reaches a brightness of up to 3000 cd/m². Quite a lot!

This phenomenon is very widely used in lighting and design rooms. Entire model lines of lamps are produced that are specially designed to be directed towards walls or ceilings, that is, it is the illuminated areas that are included in the work of general lighting of the room. The same effect is used when creating multi-tiered ceiling structures with LED strip lighting.

It is easy to guess that the illumination of the room will depend on the chosen style of its decoration. The same light bulb, say, in a white room will provide much greater illumination than in one painted in dark colors.

Since the final expected result of the operation of lighting devices is the creation of comfortable and healthy lighting indicators in the room, it is the value of surface illumination that is subject to regulation. Legislative acts (SNiP and SanPiN) indicate what illumination should be achieved in various rooms, depending on their purpose.

Thus, the current SNiP 23-05-95 in its updated version (Code of Rules SP 52.13330.2011) specifies the following standard illumination indicators for residential buildings:

Type (purpose) of the premises	Illumination standards in accordance with current SNiP, luxury
Living rooms	150
Children's rooms	200
Office, workshop or library	300
Cabinet for precision drawing work	500
Kitchen	150
Shower room, separate or combined bathroom, bathroom	50
Sauna, locker room, swimming pool	100
Entrance hall, corridor, hall	50
Entrance lobby	30
Stairs and landings	20
Wardrobe	75
Sports (gym) room	150
Billiard room	300
Storage room for strollers or bicycles	30
Technical rooms – boiler room, pump room, electrical control room, etc.	20
Auxiliary passages, including in attics and basements	20
Area at the main entrance to the house (porch)	6
Area at the emergency or technical entrance	4
Pedestrian path at the entrance to the house for 4 meters	4

In this case, the assessment of illumination should be carried out on a horizontal plane at floor height. For stairs - both at floor height and on transition platforms and steps.

To assess the level of illumination, special devices are used - lux meters. They consist of a photodetector with a spherical sensor surface, and a converter unit with an analog (arrow) or digital indication of readings.

It is clear that a lux meter is a highly professional, expensive device that is used by specialists, and which is absolutely not required to have at home. But understanding the basic photometric quantities will not hurt any owner of a house or apartment.

For what? - many may ask. Yes, at least in order to be able to independently plan the use of certain light sources in order to achieve required illumination. After all, the health and general mood of all family members directly depends on it.

The practical position of this knowledge will be discussed in the next section of the publication.

Colorful temperature

To finish the conversation about the main characteristics of light sources, it is necessary to dwell on their color temperature.

With completely equal indicators of the emitted luminous flux, one light bulb can give a warm yellowish color, another - a neutral white, and a third, for example, can glow with a cold shade of blue. How to distinguish them by this parameter? A special color temperature scale has been developed for this purpose.

Let's make a reservation right away - there is no connection between the air temperature in the room or the heating temperature of the light source itself. The glow of a physical body heated to high temperatures is simply taken as a standard.

Any body, if its temperature is above absolute zero, is itself a source infrared radiation. As the temperature rises, the wavelength of this radiation changes, and at a certain moment it reaches the visible part of the spectrum.

Probably everyone has observed this - when heated, a metal rod first turns red, then begins to glow with a bright red light; you can heat it, as they say, “white-hot.” And when performing electric welding work, when the arc temperature reaches very high levels, the melting metal can acquire a blue tint.

It is this gradation that forms the basis of the color temperature scale. It is indicated in Kelvin - and on the scale you can see what kind of glow the lamp will emit.

This color temperature is usually indicated in the lamp labeling. Sometimes it is accompanied by a text explanation, or even a miniature scale showing in which region of the visible spectrum the lamp will glow.

The choice of lamps based on their color temperature depends on what kind of environment you plan to maintain in the room. Of course, a subjective factor will also play a significant role here - that is, the preferences of the owners. And there are no ready-made “recipes” for this. But the table below provides a recommended overview of lamps based on their glow. Perhaps this will help someone when choosing.

Colorful temperature	Visual perception	Possible definitions of the created atmosphere	Typical Applications
2700 K	Warm light	Open, warm, friendly, cozy, relaxing	Living rooms, hotel lobbies, small boutiques, restaurants, cafes
3000 K	White light	Intimate, friendly, conducive to communication	Living rooms, libraries, shops, offices
3700 K	Neutral light	Friendly, conducive to communication, giving a feeling of security, increasing attentiveness	Museums and exhibition halls, bookstores, offices
4100 K	Cold light	Focus-promoting, clean, clear, productive	Training premises, design bureaus, offices, Bolgitsy, large stores, train stations
5000 - 6500 K	Cold daylight	Disturbing, overly bright, emphasizing colors, sterile, tiring over time	Museums, jewelry stores, some offices in medical institutions

Carrying out independent calculations.

As promised, this section of the publication will discuss the algorithm for calculating illumination. More precisely, to be more correct, the calculation has just the opposite direction. That is, we already know the normal illumination value. And calculations should lead us to the result of how many lamps and with what luminous flux will be required to provide it.

General formula for calculations

So, let's start with the formula that will serve as the basis for our calculations.

Fl = (En × Sp × k × q) / (Nc × n × η)

Fl- this is the luminous flux of the lamp that needs to be installed in the lamp. That is, this is the very value that is the purpose of the calculations.

Yong- standard illumination of surfaces, depending on the type of room. It corresponds to the parameters established by SNiP and given above in the table. That is, we start from the standard value.

Sp- area of ​​the illuminated surface. Usually the area of ​​the room appears here if calculated general lighting. But if the goal is to calculate the illumination of a local area (for example, working area), then it is the area of ​​this zone that is substituted.

k- correction factor, which is often called the safety factor. Its introduction takes into account several circumstances affecting the luminous efficiency of lamps. Firstly, many lamps begin to waste their emitting potential over time, or, simply put, to dim. Secondly, some external factors can also affect the emissivity - dustiness of the room or, say, a high concentration of steam, which prevents the free propagation of light rays.

Since we are talking about residential premises, where dense steam should not exist, and dust is removed by regular cleaning, then the second group of factors can be discounted. And for the gradual loss of emissivity, the coefficient for different types lamps can be adopted as follows:

Fluorescent lamps (gas discharge): 1.2;

Conventional incandescent and halogen lamps: 1.1;

LED lamps: 1.0.

q- a coefficient that takes into account the uneven glow of certain types of lamps. It is taken equal to:

For incandescent lamps and gas-discharge mercury lamps: 1.2;

For compact fluorescent incandescent lamps and LED light sources: 1.1.

Let's move on to the denominator of the fraction.

Nc- the number of lighting fixtures planned for installation in the room or in a separate area for which the calculation is being carried out.

n- the number of horns in the lamp planned for installation.

It is probably clear that the product of the last two values ​​shows how many lamps are planned for installation. For example, one five-arm chandelier is installed. Then Nc=1, and n=5. Or you plan to illuminate the room with two devices, each with three light bulbs: Nc=2, a n=3, But if the lighting is provided by one device with one lamp, both of these quantities will be equal to one.

η - luminous flux utilization factor. This correction value takes into account many factors relating to both the characteristics of the room and the specifics of the lighting fixtures planned for installation.

Since it is precisely this coefficient that remains an unknown quantity, calculations should begin with it.

Finding the luminous flux utilization factor

This value can be called a tabular empirical value. It depends on the area of ​​the room, and on the location of the lamp, and on the main direction of the light flux, and on the finishing of the flux surfaces, walls and floors.

First of all, to enter the table you will have to define the so-called premises index. It takes into account the dimensions of the room, moreover, precisely in the ratio of length and width, since in square room and in an elongated rectangular shape the light flux will still spread differently. And secondly, it takes into account the height of the lamp above the illuminated surface. As we remember, according to SNiP requirements, illumination is assessed on a horizontal plane at floor level.

Important – sometimes the height of the ceiling in a room is confused with the height of the lamp installation. But this is still not the same thing! For example, a lighting fixture can be mounted on a wall (sconce), mounted on a stand, or placed on a table or bedside table (floor lamp or desk lamp), suspended from the flow at a certain distance from ceiling surface(chandelier).

The formula probably won't tell you anything. It’s better to suggest using an online calculator to determine this room index.

Surely you already know that too dim or, conversely, too bright lighting in a room has a negative effect on the human body. In addition to eternal drowsiness, an insufficient amount of artificial and natural light entails more serious dangers - blurred vision and impaired psychological state. Solving the problem is quite simple - install more suitable lamps and properly organize the lighting in each room. However, before this, you need to find out what lighting standards exist for residential premises. This is exactly what we will talk about now.

What does SNiP say?

The main document that specifies existing standards is SNiP (building codes and regulations). So, according to this document, the following standards of illumination in lux (Lx) must be observed in an apartment and a private house:

• attic and basement passage – 20;
• toilet, shower, bath – 50;
• hall, corridor – 50;
• wardrobe – 75;
• bathhouse, swimming pool – 100;
• bedroom, kitchen – 150;
• children's - 200;
• personal office, library, utility room, room with billiards - 300.

We draw your attention to the fact that in the bathroom you can optionally increase artificial illumination to 100 Lux, because... for applying makeup and shaving, the value specified in SNiP 05/23/2010 may not be enough.

So that you understand how to convert the provided numbers into more familiar values, remember - 1 Lux is 1 Lumen/1 square meter of room. Each light bulb must indicate such a characteristic as luminous flux (in lumens, Lm). All you need to do is first calculate the standard illumination of a living space, in your case one of the rooms, then convert the value to Lumens and select the appropriate light bulbs. Let's look at the calculation technology using an example.

We make calculations

Let's say you need to find out the standard of illumination in a bedroom whose area is 20 m2. First of all, we multiply the norm according to SNiP for this room by the area, namely 150 * 20, in total we get 3000 Lux. Accordingly, with this value, the total luminous flux of the lamps should be 3000 Lm. All you have to do is choose the appropriate light bulbs for your living space, for example, if you want, you can use 3 light bulbs of 12 W each, which in total will give no more than 3600 Lm according to the table:

This calculation is approximate, because Each has its own meanings, which you can find out upon purchase. Thus, you can easily make the artificial light in the room the kind recommended by the lighting standards for residential premises according to SNiP.

By the way, this value can be measured using special device- a lux meter, which is quite simple to use, as proven by the video below.

Measuring work

Poor lighting in premises, a workplace or a room in an apartment negatively affects human health, reduces concentration, performance, irritability and mental disturbances. Very bright light is also an irritant and does not provide anything positive for a person.

Therefore, it is necessary to ensure normal illumination of the premises, which is regulated by a certain SNiP standard. This requires easy installation appropriate lighting lamps for each room.

Illumination of premises in nominal terms is the flux of light that is emitted onto the surface at right angles per unit area. When light falls at an acute angle, the illumination decreases depending on the angle of inclination.

Illumination is measured in lux, which is equal to 1 lumen (unit of luminous flux) per m2.

The illumination of the premises directly depends on the strength of the light that comes from the source. The greater the distance from the light source to the surface, the lower the illumination parameter.

Norms

Each type of room has its own lighting standards. For example, for a grocery store, the highest pulsation value is set to 15%, illumination is 300 lux, but for the sporting goods department or building materials the norms are completely different. The rules also establish certain permissible illumination for clinics, kindergartens, car services and other facilities.

Example of illumination calculation

Let's determine the required lighting for the bedroom. The bedroom area is 25 m2. The value of the norm according to the rules for rooms of this type is multiplied by the area: 150 x 22 = 3300 lux. The total luminous flux of lighting devices at this level of illumination must be at least 3300 lumens.

Now all that remains is to choose the right lighting lamps for the bedroom. When choosing, you can, for example, purchase three such 12-watt lamps. This will ensure the creation of a luminous flux of 3600 lumens, as can be seen from the table values.

This calculation is approximate, since LED bulbs have different light parameters depending on the manufacturer. Thus, you can easily independently calculate the required power and type of lamps to create standardized illumination of any room in accordance with the rules of SNiP.

Instruments for measuring illumination

To measure room illumination, various devices are used, which have their own design features and measurement methods. Let's look at the main devices in more detail.

Luxmeter

Lux meters are divided into electronic and analog, which are no longer produced, and only old samples of such models remain.

This lux meter is used:

• Checking compliance of room illumination with regulatory data.
• Measuring lighting parameters when carrying out work to assess working conditions.
• During electrical installation work to compare illumination indicators with calculations for lighting devices.

The principle of operation of the lux meter is based on the operation of the built-in one, to which the flow of light is directed. In this case, a significant flow of charged particles appears in the photocell. As a result, a current appears electric current, the strength of which depends on the strength of the luminous flux directed at the photocell. Usually this parameter is displayed on the instrument scale.

Types of lux meters

Depending on the location of the sensor that measures room illumination, lux meters are divided into types:

Monoblock (one-piece device) . The sensor is fixed in the device body itself.

Device with remote sensor , connected by a flexible wire.

To produce simple measurements a regular monoblock lux meter is suitable, without auxiliary various functions. To determine several illumination parameters when performing professional calculations, it is necessary to use devices that have an additional set of functions. Such devices have built-in memory and can determine average parameter values.

A significant advantage for a lux meter is the presence of special light filters, which help to more accurately determine the value of the light intensity that comes from lighting devices with different shades colors.

The presence of a remote sensor in the lux meter makes it possible to determine the illumination with greater accuracy, since in this case the influence external factors decreases. Modern models have a liquid crystal display. It makes it much easier to take readings from the device.

Devices for photographic equipment

Photographic equipment uses devices such as exposure meters and exposure meters . They are designed to determine the parameters of brightness and exposure illumination. By determining the values ​​of these indicators, a professional photographer can obtain high-quality photographs.

Exposure meters are divided into types:

• Internal.
• External.

Flash meters

Such devices are designed to measure illumination when photographing. Wherein additional element use pulsed-type lighting devices (photo flashes). In modern camera models, the flash meter is located in the body. It changes the flash output at different light levels.

Professionals use flash meters with a remote sensor; they more accurately determine the illumination.

Photometer

Such a device is called a multimeter. He is more modern model flash meter. Its advantage is the combination of exposure meter and flash meter options.

Light pulsation

The uniformity of the luminous flux of lighting devices leaves much to be desired. The effect, expressed in the presence of fluctuations in the light flux, is not visible to the eye, but its impact on human health is of great importance.

The danger of such light is that it is visually impossible to determine the presence of light pulses. And as a result of their action, sleep may be disrupted, discomfort, depression, weakness, heart failure and other symptoms may occur.

The pulsation parameter is its coefficient, which expresses the force of change in the flux of light directed per unit surface area over a period of time. The formula for calculating this coefficient is quite simple. The irradiance ripple factor is determined by the difference between the highest and lowest illuminance for a certain time, divided by twice the average illuminance, and the result is multiplied by 100%.

Sanitary regulations determine the upper limit of the pulsation coefficient. In the workplace it should be no more than 20%, and depends on the degree of responsibility of the employee’s work. The more responsible the work, the lower the lighting pulsation coefficient should be.

For administration premises and offices with intense visual work, this coefficient should not rise above the 5% mark. In this case, the flow of light with a pulsation frequency of up to 300 hertz is taken into account, since there is no point in taking a higher frequency into account, due to the fact that it is not perceived by the human eye and does not have a negative effect.

Determination of lighting pulsation

To determine the pulsation of light, an effective simple device is used that measures the brightness, pulsation and illumination of rooms, and is called a luxmeter-pulsometer-brightness meter.

Device functions

• Measuring the pulsation of light waves that occur when various lighting devices flicker.
• Measuring the lighting pulsation of computer monitors and other screens.
• Determination of room illumination.
• Determining the brightness of lighting devices and monitors.

The operating principle of the device is to check the lighting level using a photosensor with further signal conversion and displaying the result on a liquid crystal display.

The light pulsation coefficient can be determined using a program on a computer, or you can analyze the measurements yourself. To analyze measurements on a computer, a special program “Ecolight-AP” is used, which works with the device “Ecolight-02”.

Distinctive features measuring instruments The factors that determine ripple are sensitivity levels, type of power supply and quality of photosensors.

The highest pulsation coefficient is produced by LED lamps, when using which this parameter sometimes reaches 100%. and have a low pulsation coefficient. Incandescent lamps have a pulsation coefficient of no higher than 25%. In this case, the cost and quality of the lamps do not play a role. Even expensive lamps can produce significant levels of light pulsation.

Methods for reducing lighting pulsation

• The use of lighting devices operating on alternating current with a frequency of more than 400 hertz.
• Installation of lighting fixtures for different phases with a three-phase network.
• Installation of a ballast compensation device () into the lighting device and special connection of offset lamps. The first lamp operates on a lagging current, and the 2nd on a leading current.
• Installation of lamps with electronic ballasts. They are equipped with an electronic ballast that smooths out ripples and stabilizes the voltage.

If lighting devices in a room are connected to one phase, then connecting them to different phases will be problematic. Therefore, it will be more convenient to purchase luminaires with electronic ballasts. Their advantage is that they comply with all regulations.

Controlling the level of lighting pulsation is necessary for human health, since deviations from the norms lead to disruption of the performance and well-being of employees.

For residential buildings, indoor lighting is also important. The pulsation of light is not visible, but over time its negative impact becomes apparent.



Lux (unit of illuminance) Lux(from Latin lux ≈ light), unit of illumination in International System of Units. Abbreviated designation: Russian lk, international lx. 1 L. ≈ illumination of a surface with an area of ​​1 m2 with a luminous flux of radiation incident on it equal to 1 lm. ═ 1 L. = 10-4 phot (unit of illumination GHS system of units).

Big Soviet encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Lux (unit of illumination)" is in other dictionaries:

Lux (symbol: lx, lx) is a unit of measurement of illumination in the SI system. Lux is equal to the illumination of a surface with an area of ​​1 m² with a luminous flux of radiation incident on it equal to 1 lm. Multiples and submultiples Decimal multiples and submultiples ... Wikipedia

1. lux, constant (luxuriously equipped); cabinlux 2. luxury, a (hotel room, cabin, compartment, etc. of the highest category); live in a suite 3. suite, a; R. pl. ov, counting f. lux (unit of illumination) ... Russian word stress

1. LUX, a; m. [from lat. lux light] Phys. Unit illumination measurements. 2. LUX [from French. luxe luxury]. I. unchanged; in zn. adj. Luxuriously, comfortably equipped, distinctive high quality. Coupe l. Cabin l. Hotel l. II. A; m. Razg... ... encyclopedic Dictionary

1) (Latin lux light) a unit of illumination in the international system of units (si), equal to the illumination of a surface with an area of ​​1 m2 with a luminous flux of radiation incident on it equal to 1 lumen; abbr. designations: lx, lx. 2) (French luxe luxury lat.… … Dictionary of foreign words of the Russian language

LUX, ah, husband. (specialist.). Unit of illumination. II. LUX 1. a, husband The best hotel room, carriage, salon, cabin in terms of equipment and service. Live (drive, sail) in a luxury. 2. unchangeable Highest class, category, grade. Cabin l. Chocolate l. Atelier l. |… … Ozhegov's Explanatory Dictionary

LUX 1, a, m. (special). Unit of illumination. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary

This term has other meanings, see Lux (meanings). The request "lk" is redirected here; see also other meanings. Lux (from Latin lux light; Russian designation: lk, international designation: lx) unit of measurement... ... Wikipedia

I (French luxe luxury, splendor, from the Latin luxus splendor) designation of luxuriously equipped stores, hotels, compartments, cabins, and some goods. II (from the Latin lux light) unit of illumination in the International System... ... Great Soviet Encyclopedia

Light and radiation
Light is defined as electromagnetic radiation that causes a visual sensation in the human eye. In this case, we are talking about radiation in the range from 360 to 830 nm, which occupies a tiny part of the entire spectrum of electromagnetic radiation known to us.
Luminous flux F
Unit of measurement: lumen* [lm]. Luminous flux Ф is the entire radiation power of a light source, estimated by the light sensation of the human eye. A conventional 100 W incandescent lamp produces a luminous flux of approximately 1300 lm. A compact fluorescent fluorescent lamp with a power of 26 W creates a luminous flux of approximately 1600 lm. The luminous flux of the Sun is 3.8? 1028 lm.
Light intensity I
Unit of measurement: candela** [cd]. The light source emits luminous flux F in different directions with different intensities. The intensity of light emitted in a certain direction is called luminous intensity I.
Illumination E
Unit of measurement: lux*** [lx]. Illumination E reflects the ratio of the incident luminous flux to the illuminated area. Illumination is equal to 1 lux if the luminous flux of 1 lm is evenly distributed over an area of ​​1 m2
Brightness L
Unit of measurement: candela per square meter [cd/m2]. The luminous brightness L of the light source or illuminated area is the main factor for the level of light sensation of the human eye.
Colorful temperature
Unit of measurement: Kelvin**** [K]. The color temperature of the light source is determined by comparison with the so-called "black body" and is displayed by the "black body line". If the temperature of the “black body” increases, then the blue component in the spectrum increases, and the red component decreases. An incandescent lamp with warm white light has, for example, a color temperature of 2700 K, while a fluorescent lamp with daylight color has a color temperature of 6000 K.

Common colors of light
There are the following three main colors of light: warm white 5000 K.

Color rendition
Depending on where the lamps are installed and the task they perform, artificial light should provide the best possible color perception (as in natural daylight). This capability is determined by the color rendering characteristics of the light source, which are expressed in terms of different degrees of "general color rendering index" Ra. Color rendering index reflects the level of correspondence between the natural color of a body and the visible color of that body when illuminated by a reference light source. To determine the value, the Ra color shift is recorded using the eight standard reference colors specified in DIN 6169, which is observed when the light of the light source under test is directed towards these reference colors. The smaller the deviation of the color of the light emitted by the lamp under test from the reference colors, the better the color rendering characteristics of this lamp. A light source with a color rendering index of Ra = 100 emits light that optimally reflects all colors, like the light of a reference light source. The lower the Ra value, the worse the colors of the illuminated object are reproduced.

* 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 of one steradian (1 lm = 1 cd x sr). The total luminous flux created by an isotropic source with a luminous intensity of one candela is equal to 4n lumens.

** Candela (designation: cd, cd; from Latin candela - candle) is equal to the intensity of light emitted in a given direction by a source of monochromatic radiation with a frequency of 540·1012 hertz, the energy intensity of which in this direction is (1/683) W /avg.

*** Lux (designation: lux, lx) - a unit of illumination measurement, equal to the illumination of a surface with an area of ​​1 m? with a luminous flux of radiation incident on it equal to 1 lm

**** Kelvin (designation: K) is a unit of measurement of temperature, one kelvin is equal to 1/273.16 of the thermodynamic temperature of the triple point of water. The beginning of the scale (0 K) coincides with absolute zero. Conversion to degrees Celsius. C = K - 273.15

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

What is "luminous flux" called?

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

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

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

Luminous flux unit

How is the physical quantity in question measured?

According to current standards The SI (International System of Units) uses a specialized unit called the lumen.

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

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

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

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

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

Formula

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

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

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

What is "candela"

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

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

In fact, one candela is the intensity of light emitted by one candle (hence the name). It is worth noting that in the Russian language for a long time, instead of the term “candela”, the word “candle” was used. However, this name is outdated.

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

Lumens and Luxes

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

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

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

In simpler terms, a lumen is an indicator of the amount of light emitted by a certain source, for example, the same light bulb. But lux shows how light the room really is, since not all light rays reach the illuminated surface. In other words, lumen is the light that came out of the source, lux is the amount of it that actually reached the illuminated surface.

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

For example, when the library hall was built, many light bulbs were hung in it. General illumination this empty room was equal to 250 lux. But when renovation work were completed and furniture was brought into the hall, the light level dropped to 200 lux. This is despite the fact that the light bulbs, as before, produced the same amount of lumens of light energy. However, in the path of each of its rays, obstacles now appeared in the form of shelves with books and other library furniture, as well as visitors and employees. Thus, they absorbed part of the emitted light, reducing the total amount of illumination to the hall.

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

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

Lumen and Watt

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

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

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

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

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

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

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

Multiples of Lumen Units

Lumen, like all its “relatives” in the SI system, has a number of standard multiples and submultiples. Some are used for ease of calculation when one has to deal with either too small or too large values.

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

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

Lumen subunits

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

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

Surface illumination is the quantity

∆Φ - luminous flux incident on the surface of the area

∆S, Figure 3.3. If ∆Φ = 1lm,

∆S = 1m, illumination = 1 lux, (lux).

That is, 1lx = 1lm: 1m2.

Figure 3.3

3.2.5 Law of illumination

Elementary transformations make it possible to establish the relationship between the surface illumination E and the distance R and the angle of incidence of light j on the surface, Figure 3.3, in the form:

Formula (3.9) is called law of illumination .

3.2.6 Luminosity of the emitting surface, m

So far, we have considered point light sources. Every real source has finite dimensions. Let a luminous area of ​​area DS, Figure 3.4, emit light into a hemisphere, which corresponds to a solid angle DW = 2πavg. Let us denote by DΦ PS the luminous flux emitted by the area DS into the hemisphere.

The value, lm/m2 is called Withdecency radiating areaDS.

According to Figure 3.4, luminosity M is numerically equal to the luminous flux emitted from a unit area of ​​the luminous surface into a solid angle of 2π steradians.

Figure 3.4

3.2.7 Brightness of the luminous surface, l

Let a luminous surface of area DS emit a luminous flux DΦ into a solid angle DΩ, the symmetry axis of which makes an angle Θ with the normal to radiating surface, Figure 3.5.

Figure 3.5

Magnitude

, (3.10)

according to , is called the brightness of the luminous surface.

3.2.8 Lambert's Law

In 1760, the German scientist Lambert showed that if the area DS not only emits light, but also ideally evenly scatters it in all directions, the brightness of the radiation L does not depend on the angle Θ included in (3.10).

According to Lambert's law

L L = const, (3.11)

for any Θ included in (3.10).

Elementary transformations, , show that for a Lambertian source, the relationship between the luminosity of the emitting surface M L and its brightness L L has the form:

M L = L L × π (3.12)

3.2.9 Light exposure, ns

Light exposure H C is the product of surface illumination E and time t during which the surface is irradiated. A-priory,

H C = E × t, (lx × s) (3.13)

At the end of Section 3.2, we present in Table 3.2 the main photometric characteristics, analytical expressions for them and dimensions in “S I“.

Table 3.2 List of main photometric characteristics.

Name of photometric quantities	Analytical expression	Dimension in “SI”
The power of light		Candela, (kd)
Light flow		Lumen, (lm)
Surface illumination		Lux, (lx), (lumen per square meter), (lm/m).
Luminosity of the emitting surface		Lumen per square meter (lm/m)
Luminous surface brightness		Candela per square meter, (cd/m)

3.3 Energy characteristics of optical radiation

3.3.1 Energy exposure, N E

A value equal to the ratio of the energy of radiation DW incident on a surface to the area of ​​this surface DS:

, (3.14)

3.3.2 Radiation flux, F E

A value equal to the ratio of the radiation energy DW transferred by radiation to the transfer time of this radiation Dt

F E = , (W), (3.15)

called radiation flux.

3.3.3 Energy luminosity Є (integrated emissivity)

The integral emissivity is equal to the ratio of the radiation flux F E to the area DS I from which this flux is emitted:

3.3.4 Surface irradiance, Є O

A value equal to the ratio of the radiation flux F E to the area DS P on which this flux falls and is absorbed

Bibliography

Ignatov A.N. Fundamentals of optoelectronics. Part 1. Emitting and photo-receiving devices. – Novosibirsk, 1988.

Ignatov A.N. Fundamentals of optoelectronics. Part 2.

Liquid crystal and electroluminescent indicator devices. – Novosibirsk, 1989.

Selivanov L.V. Fundamentals of optics. Part I. - Novosibirsk: SibGATI, 1995. – 54s

Selivanov L.V. Fundamentals of optics. Part II.

– Novosibirsk: SibGATI, 1995. – 56s.

Selivanov L.V. Fundamentals of optics. Part V. - Novosibirsk: SibGATI, 1997. – 56s.

Selivanov L.V. Fundamentals of optics. Part IV.

– Novosibirsk: SibGATI, 1997. – 63s.

Goss F., Hanchen H. Ann. Phys. Ser. 6, I. – Leipzig, 1947 – 333s.

Hansperger R. Integral optics. Translation from English. – M.: MIR, 1985. – 380s.

Mahlke G., Gessing P. Fiber optic cables. Translation from English. – Novosibirsk: PUBLISHER, 1997. – 264s.

Cheo P.K. Fiber optics. Translation from English. – M.: Energoatomizdat, 1988. – 279s.

Landsberg G.S. Optics. – M.: NAUKA, 1976. – 926s.

Physical quantities. Directory / edited by Grigrieva I.S., Meilikhov E.Z. – M.: Energoatomizdat, 1991. – 1232s.