How to measure the light level in a room. Standards of room illumination and lighting pulsation

On the front panel of the meter there are switch buttons and a plate with a diagram linking the action of the buttons and the attachments used with the measurement ranges.

The magnetoelectric system device has two scales: upper 0-100 and lower 0-30. On each scale, dots mark the beginning of the measurement range: on the 0-100 scale, the dot is above the 20 mark, on the 0-30 scale, the dot is above the 5 mark. The device has a corrector for setting the needle to the zero position. On the side wall of the meter body there is a plug for connecting a selenium photocell.

The selenium photocell is housed in a plastic case and is connected to the meter by a cord with a socket that ensures the correct polarity of the connection. To reduce the cosine error, a photocell attachment is used, consisting of a hemisphere made of white light-scattering plastic and an opaque plastic ring with a complex profile. The nozzle is designated by the letter K printed on its inner side . This nozzle is not used independently, but in conjunction with one of three: other nozzles designated M, P, T. Each of these three nozzles, together with nozzle K, forms three absorbers with a common nominal attenuation coefficient of 10, 100, 1000 and is used for expansion measuring ranges.

The lux meter is calibrated without attachments in the main measurement range (5-30 lux; 20-100 lux ) and has the smallest permissible measurement error equal to ± 10%.

The order of counting the measured illumination value

Against the pressed button, the largest value of the measurement range selected with the help of an attachment (or without attachments) is determined. When the right button is pressed, against which the largest values ​​of measurement ranges divisible by 10 are marked, you should use a scale of 0-100 to read the readings. When the left button is pressed, against which the largest values ​​of measurement ranges divisible by 30 are marked, you should use a scale of 0-30. The instrument readings in divisions on the appropriate scale are multiplied by the attenuation coefficient, which depends on the attachments used and is indicated on the attachments M, P, T.

For example, the K and P attachments are installed on the photocell, the left button is pressed, the arrow shows 10 divisions on a scale of 0-30. The measured illumination is 10 * 100 = 1000 lux.

To obtain correct lux meter readings, protect the selenium photocell from excessive illumination that does not correspond to the selected attachments. Therefore, if the value of the measured illumination is unknown, start measurements by installing attachments K, T on the photocell.

In order to speed up the search for a measurement range that corresponds to the instrument readings within 20-100 divisions on a scale of 0-100 and 5-300, proceed as follows: sequentially install the KT attachments; K R; To M and with each attachment, first press the right button and then the left.

If, with K M attachments and the left button pressed, the arrow does not reach 5 divisions on the 0-30 scale, take measurements without attachments, i.e. open photocell.

When determining the illumination, install the photocell horizontally at the workplace, and take the reading from the meter, also located horizontally, at a certain distance from the photocell so that the shadow from the conducting measurement does not fall on the photocell.

When the measurement is completed:

disconnect the photocell from the lux meter;

put the attachment T on the photocell;

Place the photocell in the cover of the case.

Any light source is a source of luminous flux, and the greater the luminous flux that hits the surface of the illuminated object, the better this object is visible. And the physical quantity, numerically equal to the luminous flux incident per unit area of ​​the illuminated surface, is called illumination.

Illumination is denoted by the symbol E, and its value is found using the formula E = Ф/S, where Ф is the luminous flux, and S is the area of ​​the illuminated surface. In the SI system, illumination is measured in Lux (Lx), and one Lux is the illumination at which the luminous flux incident on one square meter of the illuminated body is equal to one Lumen. That is, 1 Lux = 1 Lumen / 1 Sq.m.

As an example, here are some typical illumination values:

Sunny day in mid-latitudes - 100,000 lux;

Cloudy day in mid-latitudes - 1000 Lux;

A bright room illuminated by the rays of the sun - 100 Lux;

Artificial lighting on the street - up to 4 lux;

Light at night with a full moon - 0.2 Lux;

The light of the starry sky on a dark moonless night is 0.0003 Lux.

Imagine sitting in a dark room with a flashlight and trying to read a book. To read, you need an illumination of at least 30 Lux. What will you do? First, you bring the flashlight closer to the book, which means the illumination is related to the distance from the light source to the illuminated object. Secondly, you place the flashlight at a right angle to the text, which means the illumination also depends on the angle at which this surface is illuminated. Thirdly, you can simply get a more powerful flashlight, since it is obvious that the illumination is greater, the higher the light intensity of the source.

Let's say a light flux hits some screen located at some distance from the light source. Let us double this distance, then the illuminated part of the surface will increase in area by 4 times. Since E = Ф/S, the illumination will decrease by as much as 4 times. That is, illumination is inversely proportional to the square of the distance from a point source of light to the illuminated object.

When a beam of light falls at a right angle to the surface, the luminous flux is distributed over the smallest area, but if the angle is increased, the area will increase, and accordingly, the illumination will decrease.

As noted above, illumination is directly related to the intensity of light, and the greater the intensity of light, the greater the illumination. It has long been established experimentally that illumination is directly proportional to the intensity of the light source.

Of course, the illumination decreases if the light is obstructed by fog, smoke or dust particles, but if the illuminated surface is located at right angles to the light source, and the light propagates through clean, transparent air, then the illumination is determined directly by the formula E = I / R2, where I is the luminous intensity, and R is the distance from the light source to the illuminated object.

In America and England, the unit of illumination used is Lumen per square foot or Foot-Candela, as a unit of illumination from a source with a luminous intensity of one candela, and located at a distance of one foot from the illuminated surface.

Researchers have proven that through the retina of the human eye, light affects processes occurring in the brain. For this reason, insufficient illumination causes drowsiness and inhibits ability to work, and excessive illumination, on the contrary, excites, helps to activate additional resources of the body, however, wearing them out if this happens unjustifiably.

During the daily operation of lighting installations, a decrease in illumination is possible, therefore, to compensate for this shortcoming, a special safety factor is introduced at the design stage of lighting installations. It takes into account the decrease in illumination during the operation of lighting devices due to contamination, loss of reflective and transmitting properties of reflective, optical, and other elements of artificial lighting devices. Surface contamination, lamp failure, all these factors are taken into account.

For natural lighting, a reduction coefficient of KEO (natural illumination coefficient) is introduced, because over time, the translucent fillers of light openings may become dirty, and the reflective surfaces of the premises may become dirty.

The European standard determines illumination standards for different conditions, for example, if in the office there is no need to examine small details, then 300 Lux is enough, if people work at a computer - 500 Lux is recommended, if drawings are made and read - 750 Lux.

Illumination is measured with a portable device - a lux meter. Its operating principle is similar to a photometer. Light hits the surface, stimulating a current in the semiconductor, and the amount of current produced is precisely proportional to the illumination. There are analog and digital light meters.

Often the measuring part is connected to the device with a flexible spiral wire so that measurements can be taken in the most inaccessible, yet important places. The device is supplied with a set of light filters to adjust the measurement limits taking into account the coefficients. According to GOST, the instrument error should be no more than 10%.

When measuring, follow the rule that the device must be positioned horizontally. It is installed one by one at each required point, according to the scheme of GOST R 54944-2012. GOST, among other things, takes into account security lighting, emergency lighting, evacuation lighting and semi-cylindrical lighting, and also describes the measurement method.

Measurements for artificial and natural are carried out separately, and it is important that no random shadow falls on the device. Based on the results obtained, using special formulas, a general assessment is made, and a decision is made whether something needs to be adjusted, or whether the illumination of the room or area is sufficient.

Andrey Povny

Lighting devices differ in design, physical properties and technical characteristics. The parameters of lighting devices raise many questions and disputes, especially the unit of illumination measurement. It is often confused with other concepts, such as luminous intensity or brightness. In addition, many consumers buy lighting fixtures based on the total value, without taking into account heat and light losses.

What is illumination

The concept of illumination is closely related to the amount of luminous flux measured in laboratories using special equipment. The illumination itself can be determined independently, and its value is taken into account by the relevant SNiPs. To calculate this parameter, use the luminous flux, measured in lumens, which is in relation to the area of ​​the illuminated surface. It should hit the surface at a 90 degree angle. Illumination is measured in special units - lux (lx).

The amount of light flux has a direct impact on the physical and psychological state of a person. Too little lighting depresses the brain, and too bright, on the contrary, has a stimulating effect on brain processes. Such a negative effect causes premature wear and tear of the body and has a detrimental effect on the organs of vision.

Therefore, when drawing up a lighting design and placement of lighting devices, a safety factor must be used that takes into account the likely drop in illumination during operation. Gradually, optical components wear out and become dirty, which leads to a decrease in the brightness of artificial light. In addition, the natural light factor decreases as the reflective properties of surrounding objects gradually change.

Illumination is primarily measured at the workplace. At the same time, sound vibrations are determined, the degree of contamination, electromagnetic and even gamma radiation are taken into account. The measurement results allow us to create the most optimal working conditions, in accordance with sanitary standards and rules.

In what units is illumination measured?

The unit of illumination measurement should be discussed in more detail. The generally accepted unit is lux, which represents the illumination when a luminous flux of 1 lumen falls on a surface of 1 m2.

How much illumination does the unit of measurement 1 lux actually include? For this purpose, it is necessary to compare several standard parameters based on human physiology, enshrined in strict medical rules and government standards. Without compliance with them, it is impossible to approve any construction project.

An illumination level of 1 lux is created by an ordinary candle located at a distance of 1 m from the illuminated surface. With the help of this simple device, it is quite possible to calibrate a homemade measuring device - a lux meter - with fairly high accuracy.

As examples for comparison, we can take several well-known types of illumination.

• Bright sunlight at noon will be 100-140 thousand lux
• Sky without clouds during the day - 6200 lux
• Table lamp illuminating the table - 500 lux
• Illumination in the shade on a sunny day - 430 lux
• The onset of twilight in the evening - 70 lux
• The beginning of the night with moonlight - 1.5 lux.

Light sources and surfaces that reflect light do not always appear as individual points. If the visual organs are able to distinguish their shape, then we will talk about another photometric quantity known as brightness. Its physical properties are similar to the intensity of light, but in this case this relationship will not be absolute. It is proportional to the area of ​​the reflecting or radiating surface.

Brightness, as a physical concept, is the only photometric quantity that the human eye can normally perceive. It is clearly manifested in the properties of large light sources, consisting of a large number of point emitters. Provided they are of the same brightness, the overall light of a large lighting fixture will be perceived as a single whole.

List of basic units of measurement

There are several basic units of measurement that characterize the parameters of light in one way or another. Among them, the most famous and widespread are the following:

• Light flow. Represents the power of light emitted. This is the visible spectrum of radiation associated with the sensation of light perceived by the human eye. This value is measured in lumens (lm). For example, the luminous flux emitted by a 100-watt incandescent lamp is 1350 lm, and by a fluorescent lamp LB40 - 3200 lm.
• The power of light. The density of the luminous flux relative to the surrounding space. At its core, it is a proportion where the luminous flux is related to the solid angle within which the radiation is uniformly distributed. The unit of measurement is candela (cd).
• Illumination. The luminous flux incident on the surface has a surface density. It is evenly distributed and correlates with the area of ​​the illuminated surface. The unit of measurement is lux (lx), equal to 1 lm/1 m2.
• Brightness. Represents the luminous intensity with surface density in a specified direction. The unit of measurement is cd/m2.
• Luminosity. The luminous flux emitted by a surface with density, which is the ratio of the luminous flux to the area of ​​the luminous surface. The unit of measurement is 1 lm/m2.

Instruments for measuring light levels

The level of illumination is measured by a device - a lux meter. This small, portable device works in much the same way as a photometer. A stream of light radiation hits a semiconductor photosensitive element and begins to tear off electrons from it, which begin to move in an orderly manner. As a result, the electrical circuit closes. In this case, the magnitude of the current is proportional to the intensity of illumination of the photocell and is displayed on the scale of analog devices.

Currently, there are practically no instruments with arrows left; they have been replaced by digital measuring equipment. Each lux meter is equipped with a liquid crystal display and a photosensitive sensor located in a separate housing. A flexible wire is used to connect these two parts together.

Before starting light measurements, the lux meter is set to a horizontal position. Modern GOST standards require that different points of the room be used for measurements in accordance with the established scheme. Natural and artificial lighting are measured separately. When performing the procedure, even the slightest shadow is not allowed to fall on the device. There should not be any sources of electromagnetic waves nearby. All these factors can cause interference and affect the measurement results.

The resulting illumination value must be compared with the parameter established by GOST. Based on these data, conclusions are drawn about the sufficient or insufficient illumination of any room or area. After the tests, an evaluation protocol is drawn up.

Illumination and LED devices

During the lighting process, LEDs generate a large amount of heat. To dissipate it, heat-conducting structures made of aluminum, cooling fins and other elements are used that neutralize the effects of heat. When creating new lamps, specialists must take into account the relationship between illumination and heat loss.

Operational difficulties appear when the temperature rises above 50 degrees. In this regard, measurements should be taken approximately two hours after the LED lamps start operating. To eliminate errors, illumination measurements are performed periodically throughout the working day. It is recommended to conduct such studies at least once a year.

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 a simple installation of 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 at 15%, illumination at 300 lux, but for a sporting goods or building materials department, the standards 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 lamps 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.

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 flow of electric current appears, the strength of which depends on the strength of the light 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 make simple measurements, a regular monoblock lux meter is suitable, without various auxiliary 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 filters that help more accurately determine the value of light intensity that comes from lighting devices with different shades of colors.

The presence of a remote sensor in the lux meter makes it possible to determine the illumination with greater accuracy, since the influence of external factors is reduced. 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 (exposimeters) . 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. In this case, pulse-type lighting devices (photo flashes) are used as an additional element. 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. It is a more modern version of the 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 disturbed, discomfort, depression, weakness, heart failure and other symptoms may occur.

The ripple 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 principle of operation 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 of measuring instruments that detect pulsations 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 smoothes 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 lamps 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.

When working with light, it is impossible to develop without daily studying trends and new products in the market. One of our latest discoveries was an application that allows you to measure the amount of light in a room using a regular smartphone. Of course, from a professional point of view, we could not remain indifferent to such a challenge. German Institute of Applied Lighting Engineering (DIAL GmbH), which examined exactly the question that interested us: can a smartphone become a worthy replacement for a lux meter?

Luxmeter versus smartphone: can a special application become an alternative to a measuring device?

If such a replacement really justifies itself, then it would not be a revolution, but at least a very profitable proposal. Judge for yourself, a lux meter is not a cheap pleasure. But almost everyone has a smartphone. And special applications are either free or cheap. Since our company works professionally with light, the idea of ​​measuring photometric parameters using a phone touches us. But, for the sake of fairness and curiosity, we decided to conduct an experiment. The purpose of the study: to compare the results of the corresponding applications with the indicators of our standard lux meter.

Equipment under test

Our experiment involved iPhones of different series, as well as Sony, Samsung and Nokia phones:

Software

We selected the following applications (most of them are free) and installed them on each of the systems:

For reference

The control measurement was carried out using a calibrated PRC Krochmann lux meter (Model 106e, special model, class A).

Light sources used

For the test we chose three different light sources:

• low voltage halogen lamp;
• compact fluorescent lamp (color temperature 2700 K);
• LED (color temperature 3000 K).

To simplify our research, we decided to leave one light source - LED.

Test conditions

The test took place in a room without sources of daylight or artificial light. We placed light sources on a horizontal surface. The illumination was alternately set to 100 lux, 500 lux and 1000 lux. The photometric head of our luxmeter was located perpendicular to the axis of the lamp. Then, in the same way, we placed smartphones with installed applications. The front camera and brightness sensor were located in the same place where the photometer was previously located.

This arrangement was suitable for all applications except the paid “Luxmeter Pro Advanced”, since it uses light reflected from the surface to measure illumination. This application also provides settings for the types of light source, distance to it, etc.

Some applications allowed calibration, and if possible, we carried it out in accordance with the manufacturer's instructions, namely at 100 lux.

results

During our testing, we found that while it was possible to calibrate to a certain value in some applications, it was difficult to accurately determine it. Thus, either the step was large, or the value of 100 lux was not set at all (for example, the maximum value that could be set on the iPhone 5 with LightMeter by whitegoods was 34 lux). Often the deviations from the control values ​​turned out to be very high (up to 113% for the Samsung Galaxy S5 with the “Lux Light Meter” application from Geogreenapps). When using the 500 lux reference, the smartphone display showed 1.063 lux. The lowest deviation of 3% was on the iPhone 5 with "LightMeter by whitegoods". At 500 lux, this smartphone showed 484 lux. At the same time, we cannot claim that this particular combination will always lead to the smallest possible deviations. When using a value of 100 lux and the same application, the deviation reached 89%, and the device showed 11 lux.

We also noticed that the displayed values ​​on devices from Sony, Samsung and Nokia were significantly higher than the reference values, while on the iPhone they were significantly lower. The average deviation in all applications on Android smartphones and on Windows Phones was approximately 60% higher than the control ones. The discrepancy between the values ​​measured by different iPhones was 60% lower than the reference values.

We also noticed that various applications installed on smartphones from Samsung and Sony showed similar values. Most likely, these devices use a brightness sensor rather than a camera to measure light.

In some Samsung models, you can switch to the engineering menu mode using the combination *#0*#. By selecting the “Light sensor” item, you can find out the expected illumination without installing the application. So in this case, a special program may not be needed. However, the performance on these devices also deviated from the reference value within the range of 37%-113%.

Will the results be the same on similar smartphones with the same applications?

To test this, we used 4 identical iPhone 5s with the "Galactica Luxmeter" and "LightMeter by whitegoods" apps installed on them. Unfortunately, we were disappointed. All four smartphones showed completely different performance.

We believe that the reason for such fluctuations is the difference in components in the phones. The user does not notice such deviations during everyday use, but during direct testing they are noticeable.

Is there always a percentage deviation from the reference value?

If you always use your smartphone with the same app, you can assume that you can make fairly accurate measurements by knowing the percentage deviation from the reference value. But is this percentage always the same?

To test this, we took illuminance measurements at 10 lux, 100 lux, 1000 lux and 10,000 lux using an iPhone 5 placed on an optical bench in a black room. The brightness increase can be very precisely set by adjusting the distance between the light source and the receiver.

The light source was again an LED light with a color temperature of 3000 K. In this test we looked at the performance of two different applications. It turned out that the values ​​of different programs deviate from each other, in some cases up to 358% (12 lux to 55 lux with a standard of 100 lux). If we consider the percentage of deviations from the reference values, we will not see any pattern.

When using the Galactica Luxmeter app, values ​​were 180% above reference at 10 lux and 50% below reference at 10,000 lux. The "LightMeter by whitegoods" was calibrated at 10 lux. At the reference 100 lux, the deviation was 88% downward, and at 10,000 lux - 59%. The values ​​of all other applications were also significantly lower than the control ones, and the percentage of deviations itself changed all the time.

Additionally, we found that measurements taken with the front and rear cameras show different values. In addition, some applications never show 0 lux, even if no light reaches the camera and it is covered with a “stub”.

Conclusion

The results prove that serious light measurements are only possible with professional equipment. It is equipped with a calibrated sensor to ensure that the illumination assessment is carried out in accordance with the sensitivity of the human eye in daylight. In addition, the devices allow you to measure the amount of light depending on the angle of incidence of the beam. Smartphones can't do either of these things, otherwise they won't be able to perform their functions as a phone.

Application developers do not claim that smartphones can replace professional devices. The statement that some devices allow calibration sounds impressive, but, unfortunately, it is technically almost impossible to set the desired value. Even when using the same application on identical smartphones, the evaluation results differ.

So, unfortunately, the apps don't really help much, even in getting a general idea of ​​the lighting. Moreover, the result may be completely opposite and mislead the user.

Therefore, if you really need to measure the illumination, use a lux meter, and leave your phone for calls to your loved ones.