For people who are constantly working in the office, the good illumination of the workplace is important. If there is little light, fatigue increases, the quality of view may be reduced. Check illumination on the desktop will help the Luximeter program, which can be put on any android smartphone.

What illumination is considered sufficient

According to Russian standards, SNiP the illumination of the desktop in the office should be about 300 LCs. But doctors advise more importance. In this, they agree with European standards, requiring at least 1000 LCs. If you take care of your health, then use a number of 300 and 1000 LCs as a guide.

To increase the amount of light, install desktop lamp. Or use more powerful light bulbs in ceiling lights.

How to measure the illumination with smartphone

Install the Luxmeter program from the official store google applications Pay. Immediately after the first switching on the screen displays the lighting intensity expressed in suites.

In the upper left corner for comparison, the light source icon is shown, which gives such a light stream. In the picture at the top of 953 lk corresponds to the sun on a cloudy day. When the phone is removed / approaching the light source, the value changes, the graph shows the graph.

According to user reviews, the application works at the level of professional devices. Indications at 1000 LCs differed by about 50 LCs, which gives the accuracy of measurements at the level of 5%. At home, such an error can be neglected.

The setting provides calibration mode. By default, the value from the phone sensor is given. But you can set a coefficient that increases or reducing the value.

Working with the light is impossible to develop without daily study of the trends and innovations of the market. One of the last of our discoveries was the application, thanks to which the amount of light in the room can be measured with the help of an ordinary smartphone. Of course, from a professional point of view, we could not remain indifferent to such a call. The German Institute of Applied Lighting Engineering (Dial GmbH), which considered precisely the question that was interested in us: Can the smartphone be worthy of the replacement of the luxmeter?

Luxmeter vs. Smartphone: Can a special application become an alternative to the measuring instrument?

If such a replacement really justifies yourself, it would not be that a revolution, but, at a minimum, a very profitable offer. Judge himself, the luxmeter - the pleasure of the cheapest. But the smartphone is almost everyone. And special applications or free, or cost cheap. Since our company is professionally working with the light, the idea of \u200b\u200bmeasuring photometric parameters with the help of the phone we will die. But, justice and curiosity for the sake of, we decided to conduct an experiment. The purpose of the study: comparing the results of the work of the relevant applications with the indicators of our regular luxmeter.

Testing equipment

In our experiment, the iPhone was attended by different series, as well as phones Sony., Samsung and Nokia:

Software

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

Name	Manufacturer	Operating system	The possibility of calibration	Price
Galactica Luxmeter.	Flint Soft Ltd.	iOS.	not	-
Lightmeter by Whitegoods.	Whitegoods.	iOS.	there is	-
LuxmeterPro Advanced	Am Powersoftware.	iOS.	there is	7,99€
Luxmeter.	Khtsxr.	Android	there is	-
Light Meter Pro.	Mannoun.net	Android	there is	-
Lux Light Meter	Geogreenapps.	Android	there is	-
SENSOR LIST.	Ryder Donahue.	Windows Phone	there is	-

For reference

The control measurement is manufactured using a calibrated LUX meter PRC KROCHMANN (Model 106e, a special model, class A).

Used light sources

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 passed indoors without day or artificial light sources. On the horizontal surface, we placed light sources. They alternately installed the illumination of 100 LCs, 500 LCs and 1000 LCs. The photometric head of our luxury was located perpendicular to the axis of the lamp. Then, in the same way, we placed smartphones with installed applications. Front-camera And the brightness sensor was in the same place where the photometer was located before.

Such a location was suitable for all applications other than paid "Luxmeter Pro Advanced", as it uses light reflected from the surface to measure illumination. This application also provides settings for the types of light source, distances to it, etc.

Some applications allowed to produce calibration, and if there was such an opportunity, we conducted it in accordance with the manufacturer's instructions, namely, 100 LCs.

results

During our test, we found out that although in some applications it was possible to calibrate to a certain value, it was definable to determine it was quite difficult. Thus, or the step was large, or the value of 100 LCs was not installed at all (for example, maximum valuewhich managed to install on the iPhone 5 with Lightmeter by Whitegoods - 34 LCs). Often deviations from the control values \u200b\u200bturned out to be very high (up to 113% Samsung Galaxy S5 with the application "Lux Light Meter" from GeogreenAnapps). When using the reference 500 LC, the smartphone display showed 1.063 LC. The lowest deviation of 3% was on the iPhone 5 with "Lightmeter by Whitegoods". At 500 LC, this smartphone showed 484 LCs. At the same time, we cannot say that it is this combination that will always lead to the smallest possible deviations. In the case of using the value of 100 LCs and the same application, the deviation reached 89%, and the device showed 11 LCs.

We also noticed that the displayed values \u200b\u200bon devices from Sony, Samsung and Nokia were significantly higher than the reference, while on the iPhone is significantly lower. The average deviation in all applications on Android-smartphones and on Windows Phone phones were approximately 60% higher than the control. The discrepancy between the values \u200b\u200bmeasured by various iPhone was 60% lower than reference.

We also noticed that various applications installed on smartphones from Samsung and Sony showed close values. Most likely, in these devices for measuring the illumination, the brightness sensor is used, and not the camera.

In some sAMSUNG models can switch to mode engineering menu Using the combination * # 0 * #. After selecting the "Light Sensor" item, you can find out the alleged illumination without installing the application. So in this case special program maybe not need. However, the indicators on these devices also deviated from the reference value within 37% -113%.

Will the results on similar smartphones with the same applications?

To check it out, we used 4 identical iPhone 5 with "Galactica Luxmeter" and "Lightmeter by Whitegoods" installed on them. Unfortunately, disappointment was waiting for us. All four smartphones showed completely different indicators.

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

Is there always a percentage from the reference value?

If you always use a smartphone with the same application, you can assume that it is possible to accurately measure measurements, knowing percentage deviation from the reference value. But does this percentage always the same?

In order to test it, we conducted the dimensions of the illumination on 10 LCs, 100 LCs, 1000 LCs and 10,000 LCs with using iPhone 5 placed on an optical bench in the black room. An increase in brightness can be very accurately set by adjusting the distance between the light source and the receiver.

A LED lamp with a color temperature of 3000 K was used as a radiation source. In this test, we considered the indicators of two different applications. It turned out, values different programs deviate from each other, in some cases up to 358% (12 LCs up to 55 LCs with a standard of 100 LCs). If we consider the percentage of deviations from the reference values, then we will not see any patterns.

When using the Galactica Luxmeter application, the values \u200b\u200bwere higher than the controls by 180% at 10 LCs and 50% below the reference values \u200b\u200bat 10,000 LCs. "Lightmeter by Whitegoods" was calibrated on 10 LCs. With a supporting 100 LC, the deviation was 88% in a smaller side, and at 10,000 LCs - 59%. The values \u200b\u200bof all other applications were as well below the control, and the percentage of deviations changed all the time.

In addition, we found that the measurements carried out using anterior and rear chamber show various values. In addition, some applications never shown 0 LCs, even if the camera does not fall on the camera and it is closed by a "plug".

Conclusion

The results prove that serious light measurements are possible only with the help of professional equipment. It is equipped with a calibrated sensor guaranteeing that the illumination assessment will be carried out in accordance with the sensitivity of the human eye in the daylight. In addition, devices allow you to measure the amount of light depending on the angle of the ray. Smartphones can not make any other, otherwise they will not be able to perform their functions as a telephone.

Application developers do not argue that smartphones can replace professional devices. The statement that some devices allow you to calibrate sounds effectively, but, unfortunately, it is technically almost impossible to install the desired value. Even when using the same application on identical smartphones, the results of the assessment differ.

Therefore, unfortunately, applications are not really helping too much, even to get a general idea of \u200b\u200billumination. Moreover, the result may be fundamentally opposite and mislead the user.

Therefore, if you really need to measure the illumination, use the luxmeter, and leave the phone for calls your favorite.

LED lighting firmly entered our life, lED bulbs Already sold even in grocery stores, and on the shelves of economic and building supermarkets lED lamps Even more than ordinary incandescent lamps and compact luminescent (energy-saving) combined.

Unfortunately, manufacturers often deceive buyers, pointing at the packaging strongly overpriced values \u200b\u200bof the light flux and the equivalent of incandescent lamps. You buy a lamp on which "600 lm, equivalent to incandescent lamps 60 W", bring it home, turn on and aware that it shines clearly to the dull than the 60-watt incandescent lamp. Fortunately, according to the Consumer Rights Act, LED lamps can be returned to any store for 14 days (and in many hypermarkets and within 30, 60 days and even years). Return is possible due to the fact that the light bulbs (including LED) are still not considered a complex technical product.

In order to understand how much in the reality of the light gives a lamp, you need to measure its light stream. Usually for measuring the light flux (the total light that the lamp gives) is used expensive laboratory equipment (goniophotometers, measuring integrating spheres), which costs tens of thousands of dollars. I offer a way that allows you to accurately measure the light flux of the lamp, spending only 87 rubles.

The main problem when measuring the luminous flux - the unevenness of the brightness of light in different directions different types lamps. Some lamps are more shine forward, some will shine more, some almost evenly shine in all directions.

To measure, it is necessary to somehow get the average brightness of the lamp. Typically, for this, the lamp is placed inside the integrating sphere, covered with super-branded matte paint from barium sulfate. The light is repeatedly reflected from the walls and falls on the sensor. The goniophotometer rotates the lamp in the horizontal plane, makes many brightness measurements at each point of rotation and calculates the total amount of light that the lamp gives. We proceed easier.

We will need a lamp with a spherical matte plastic cap. This matte cap will averaged the brightness of the lamp radiation in different directions. Such a lamp can be bought for 87 rubles in Lerua Merlen stores. In the picture there is another lamp with a glass beam - do not pay attention: in the stores themselves what is needed.

Accurate climbing of the lamp - "NBB-60 lamp (direct base) Ball plastic, white", manufacturer LLC "Axioma", Moscow.

Almost any smartphone on Android can be used as a brightness meter (luximeter). Most smartphones have a light sensor (it is located above the screen), which is used to adjust the brightness of the screen depending on the external lighting.

IN Play Market. there are many program-luxury programs, I recommend setting a simple and convenient program SENSORS MULTITOOL. After starting the program, go to the LIGHT tab and see the illumination value. Luxmeter in all smartphones are not calibrated, and different smartphones It will show completely different values \u200b\u200bthat may differ from the actual twice, but the accuracy of our measurements will not affect.

Fix the lamp on any surface (I used a piece of plywood). Smartphone attach two rubber bands to a package of milk or juice.

For measurement, we need a reference lamp. I recommend using the IKEA 600 LM lamp 303.059.76 LED1466G9. This lamp has a light stream, exactly corresponding to the declared, and a very small spread over a light flow in different instances.

Of course, it is possible to use a conventional incandescent lamp, but it is important to remember that, firstly, the light flow of incandescent lamps is very much depends on the voltage on the network, and secondly, different copies of the production of Russian and Belarusian plants can vary greatly through the light stream. Nevertheless, you can always find out, more or less light gives an LED lamp compared to the incandescent lamp.

We spin the ceiling, turn on the lamp, placing the fixed smartphone opposite the lamp, run the program. We calibrate our measurement system: we move the package with a fixed smartphone so that the smartphone luxury show is exactly 600 lux (if we have a lamp 600 lm as a reference. Now I will unscrew the reference lamp and screw the lamp that we want to check without changing the distance between the lamp and the smartphone. The smartphone will show the value that will correspond to the lighting light of the measured lamp.

I checked this simple measuring installation on seven lamps with a light flux from 200 to 1000 lm and two smartphones - Sony Z3 Dual and ZUK Z1. Measurement accuracy was 1-15%.

The LED lamps have one feature - as they warm up, their light stream is reduced by 11-12% for half an hour. We measured the lamps immediately after switching on, but since the reference lamp was cold, our entire measuring system was more or less accurate.

Increase the measurement accuracy, if you use any luxmeter instead of a smartphone. Even the cheapest Chinese is suitable for $ 10. It can be badly calibrated, but this will not affect the accuracy of our measurements. The reference lamp and those lamps whose light flux we want to measure is better to warm up for half an hour. A luxmeter needs to be also hard to fasten and arrange at such a distance from the lamp so that it show exactly so many suites, how many lumens give a reference lamp.

I measured the light stream of the same seven lamps using the Lupin Pulsmeter Luxemeter.

The measurement accuracy has become significantly higher - the error is only 0-3%.

I note that all official accredited laboratories also have discrepancies in the measurement. In the picture below, the results of measuring the light stream of the same lamp in 54 different laboratories. On average, the discrepancy was 3%, the maximum as possible.

So, "on the knee", I managed to achieve the accuracy of measurements that not all laboratory boasts.

This article is an translation articles Luxmeter App Versus Measuring Device:
Are Smartphones Suitable for Measuring Illuminance?

For smartphones there are many applications that facilitate our lives. There are many applications for lighting. But does this mean that you can use a smartphone to measure illumination?

We ask this question more and more often, because the benefit is obvious. After all, these applications are free or not very expensive. It would be great to replace the luxmeter, which, depending on the manufacturer and accuracy, costs from 100 to 2000 euros (Aliexpress disagree and shows the amounts even less than 10 euros), on the app for a smartphone, which is also almost every one.

As an accredited lighting laboratory, we can only smile the idea of \u200b\u200bmeasuring illumination with a smartphone. Nevertheless, it seemed to us this idea very curious, which prompted us to conduct an experiment. Thus, we started looking for various applications for various operating systems. We wanted to find out how accurately they are measured compared to the luxmeter from our laboratory.

Hardware

For this test we used various models iPhone, as well as: Sony, Samsung and Nokia.

manufacturer	Operating system
iPhone 5.
iPhone 5S.
iPhone 6.
Sony Xperia Z 1	Android
Sony Xperia Z 2	Android
SAMSUNG GALAXY S 5	Android
Nokia Lumia 925.	Windows Phone

Software
We have installed the following applications, most of which are free:

Program	Developer	Operating system	The possibility of calibration	Price
Galactica Luxmeter.	Flint Soft Ltd.		not	is free
Lightmeter by Whitegoods.	Whitegoods.		yes	is free
LuxmeterPro Advanced	Am Powersoftware.		yes	7,99 €
Luxmeter.	Khtsxr.	Android	yes	is free
Light Meter Pro.	Mannoun.net	Android	yes	is free
Lux Light Meter	Geogreenapps.	Android	yes	is free
SENSOR LIST.	Ryder Donahue.	Windows Phone	yes	is free

Reference device

We conducted control measurements with a luxmeterPRC KROCHMANN (Model 106e, Special Model, Class A) And, of course, the device was calibrated.

Used light sources

For this test, we chose three different light sources:

· low-voltage halogen lamp

· compact fluorescent lamp (color temperature: 2700 K)

· LED (Color Temperature: 3000 K)

What would not complicate the article we left onlyLED source.

Our test installation

The test passed in a dark room without sources of artificial and naturally light. For used light sources, we set the illumination alternately on 100 LCs, 500 LCs and 1000 LC (probably still 2000) on a horizontal surface. To do this, the photometric head of the luxmeter was located perpendicular to the axis of the lamp.

Then, smartphones with various applications also prevented so that the front camera and the brightness sensor were under the luminaire. The sensor or front camera was located exactly in the point where the photometric head of the luxmeter was previously located.

So all the devices were located, exceptiPhone. with a paid application "Luxmeter Pro Advanced" as this application for measuring the illumination involves the measurement of the light reflected from the surface. There are many settings in this application including the types of light sources, the distance to the light source, etc.

Also, when using some applications, calibration is possible. Calibration was carried out in accordance with the instructions, namely 100lk.

Evaluation

During our test, we found out that, although calibration in some applications was possible to a certain value, it was not possible to set the value definitely. This happened due to the fact that the step with which the value was set was large, or the value of 100 liters was not established at all, for example in the applicationLightmeter by Whitegoods. For iPhone 5, the value for calibration was managed to set the maximum on 34lk.

Deviations from reference values \u200b\u200bwere sometimes very high (up to 113% of Samsung Galaxy S5 with the Lux Light Meter application from GeogreenAnapps). When installing the reference value of 500 LCs, a value of 1.063 LC was displayed on the smartphone display. The lowest deviation in percent (3%) was recorded when using iPhone 5 and applications "Lightmeter by Whitegoods » . When installing the reference value of 500 LCs, this smartphone showed 484 LCs. However, we cannot make a conclusion that this smartphone with a specific program will always show the correct value. When setting the illumination per 100 tier and, when used, the same applications on the same smartphone deviation reached 89% and the device showed 11 LCs.

We managed to identify the tendency that the displayed values \u200b\u200bon devices from Sony, Samsung and Nokia were significantly higher than reference values, while usually oniP. hone The displayed values \u200b\u200bare significantly lower than reference values. Average deviation from the reference value measured in all applications on Android smartphones and on Windows phonesPhone were an average of 60% higher than reference values.

The average deviation of all values \u200b\u200bmeasured by variousiPhone. it was 60% lower than reference values. We also noticed that various applications installed on smartphones from Samsung and Sony showed close values. It seems that in these models, the brightness sensor is used for measurement, and not the camera.

In some Samsung models, you can switch to the engineering menu mode - using a kit with a combination keyboard * # 0 * #. Seving the menu item "Light Sensor", you can find out the alleged illumination without installing the application. So installing applications in this case It will be superfluous. However, all the values \u200b\u200bdisplayed by these devices also deviated from 37% to 113% of the reference value. Galactica Luxmeter »and" Lightmeter by Whitegoods " Unfortunately, frustration was waiting for us here. The diagram shows that four smartphones that we tested showed in some cases completely different measurement results.

We suspect that the reason for these oscillations is to use components other than each other that the user does not notice in everyday use, but that becomes noticeable with direct comparison.

Does the dynamics of percentage deviations be saved from the reference value?

If you always use a smartphone with the same application, you may assume that it is possible to accurately measure measurements if you already know the percentage of the reference value.

But is it always the same percentage on which the value is rejected? In order to answer this question, we conducted light measurements on 10 LCs, 100 LCs, 1000 LCs and 10,000 LCs using iPhone 5 located on an optical bench in our black room. Brightness increment can be very accurately set by adjusting the distance between the light source and the receiver. A LED light source was used as a radiation source with a color temperature of 3000 K.

In this test, we reviewed the readings of two different applications. As experience shows, the values \u200b\u200bof the applications are deviated from each other - in some cases up to 358% (values \u200b\u200brange from 12 Lux to 55 LCs with a standard value of 100 LCs), if we look at the percentage of deviations from the reference values, then we will not see any patterns .

When using the application " Galactica Luxmeter »Values \u200b\u200bwere higher180% of references at 10 LCs and 50% lower than reference values \u200b\u200bat 10,000 LCs.

When using the application "Lightmeter by Whitegoods. »Calibrated for 10 LCs. In the reference value of 100, the deviation was 88% in a smaller side, and at 10,000 LCs 59%. The values \u200b\u200bof all the rest are applied as much lower. For all other values, the readings were as lower.

It is quite by chance that we found that measurements carried out using the front and rear chamber show various values. In addition to this, some applications never shown 0 LCs, even if no light falls on the camera, and it is closed by the "plug".

Conclusion

The results prove that serious light measurements are possible only with the help of professional equipment. It is equipped with a calibrated sensor, which ensures that the illumination assessment will be carried out in accordance with the sensitivity of the human eye.

In addition, devices make it possible to assess the illumination depending on the angle of the ray. Smartphones can not make any other, since otherwise they will not be able to perform their functions.

Despite the fact that the developers claim that they can replace professional devices, since their applications have various smart functions of the calibration type, but the chipping does not allow you to set exact values. And if it is possible, then deviations occur during measurements. Even when using the same application and identical smartphones, different measurement results are obtained.

Therefore, unfortunately, applications are actually useless - even just to get a general idea of \u200b\u200billumination.

from Thomas Pittner and Jaqueline Goldschmidtabout