Application for measuring illumination for Android. Is it possible to measure illumination using a phone? Will the results be the same on similar smartphones with the same applications?

Is it worth buying expensive equipment for measuring illumination if smartphone manufacturers have developed special programs that allow you to take measurements using a regular smartphone?

Let's look into this topic.
On the website of one of the smartphone manufacturers they write: “In order not to find yourself in a difficult situation, this problem is usually solved using a special device - a lux meter, but today it is better to replace expensive equipment with an iPhone application of the same name, which can be downloaded from the App Store...”
"The Luxmeter application uses data obtained from the front or rear camera of a smartphone to determine the degree of illumination, and is a real pocket illumination meter. The program is calibrated using the ATT-1508 lux meter: the calibration sample is 5000 measurements, and the coefficient of determination is 0.87 (with the following updates - 0.9 over the entire measurement range) - all this guarantees exceptional measurement accuracy."
Or we read “The Luxmeter application was created so that its users can save on the purchase of expensive professional equipment”!!!
Do you believe this? I doubted it for a very long time. Maybe they really write. I somehow downloaded a program and measured the illumination. I received 53 lux on my desktop and decided that not everything was going smoothly. But I decided that I should try it and compare it with a good lux meter, but still didn’t get around to experimenting.
And finally, the company DIAL, a professional in the field of lighting technology, which developed the DIALux and DIALux evo program, which has its own laboratory and carries out measurements and scientific activities, got down to business and tested smartphones and applications for measuring lighting.
Participants in the experiment:

Manufacturer	Platform
iPhone 5	iOS
iPhone 5S	iOS
iPhone 6	iOS
Sony Xperia Z 1	Android
Sony Xperia Z2	Android
Samsung Galaxy S5	Android
Nokia Lumia 925	Windows Phone

Software:

Name	Manufacturer	Platform	Calibration capability	Price
Galactica Luxmeter	Flint Soft Ltd.	iOS	No	for free
LightMeter by whitegoods	Whitegoods	iOS	Yes	for free
LuxMeterPro Advanced	AM PowerSoftware	iOS	Yes	7,99€
Luxmeter	KHTSXR	Android	Yes	for free
Light Meter Pro	Mannoun.Net	Android	Yes	for free
Lux Light Meter	Geogreenapps	Android	Yes	for free
Sensor List	Ryder Donahue	Windows Phone	Yes	for free

For the experiment, lighting levels were measured from 3 types of lighting sources: a low-voltage halogen lamp, a compact energy-saving lamp (2700K) and an LED lamp (3000K).
For ease of understanding, see the results for LED in the graph. That is, measurements were carried out for all lamps, but the results were published only for the light source: LED.

Measurements were carried out for all smartphones. For this purpose, in a special laboratory, illumination levels of 100 lux, 500 and 2000 lux from the tested light source were planned.
The results are surprising. In only one case, when measuring 500 lux, the iPhone5 smartphone showed a result of 484 lux, which is a very close value. In all other cases, measurements were in the range from 37 to 113%.
After these results, DIAL decided to test several identical iPhone 5 smartphones and the “Galactica” and “LightMeter by whitegoods” applications.

Unfortunately, there was no uniformity of results here either.
DIAL experts conclude that, unfortunately, in non-professional or domestic conditions, measuring light levels using smartphones should not be done. Based on experiments with various smartphones and various software, it was revealed that such measurements have neither accuracy nor correctness. It all depends on the case.

Based on the article: "Luxmeter-App vs. Messgerät: Sind Smartphones zum Messen geeignet?" by Jaqueline Goldschmidt and Thomas Pittner
Photos from DIAL.de

This article is translation articles Luxmeter App versus measuring device:
Are smartphones suitable for measuring illuminance?

There are many applications for smartphones that make our lives easier. There are many applications for lighting engineers. But does this mean that you can use a smartphone to measure light?

We ask this question more and more often because the benefits are obvious. After all, such applications are free or not very expensive. It would be great to replace the light meter, which, depending on the manufacturer and accuracy, costs between 100 and 2000 euros (Aliexpress does not agree and shows amounts even less than 10 euros), to an application for a smartphone, which almost everyone already has.

As an accredited lighting laboratory, we can only smile at the idea of ​​measuring light levels using a smartphone. Nevertheless, we found this idea very interesting, which prompted us to conduct an experiment. So we started looking for different applications for different operating systems. We wanted to find out how accurately they measured compared to the lux meter from our laboratory.

Hardware

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

manufacturer	operating system
iPhone 5
iPhone 5c
iPhone 6
Sony Xperia Z 1	Android
Sony Xperia Z2	Android
Samsung Galaxy S5	Android
Nokia Lumia 925	Windows Phone

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

Program	Developer	operating system	Calibration capability	Price
Galactica Luxmeter	Flint Soft Ltd.		No	for free
LightMeter by whitegoods	Whitegoods		Yes	for free
LuxMeterPro Advanced	AM PowerSoftware		Yes	7,99 €
Luxmeter	KHTSXR	Android	Yes	for free
Light Meter Pro	Mannoun.Net	Android	Yes	for free
Lux Light Meter	Geogreenapps	Android	Yes	for free
Sensor List	Ryder Donahue	Windows Phone	Yes	for free

Reference device

We carried out control measurements using a lux meterPRC Krochmann (Model 106e, special model, class A)And, of course, the device was calibrated.

Light sources used

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)

In order not to complicate the article, we left only LED source.

Our test setup

The test took place in a dark room without sources of artificial or natural light. For the light sources used, we set the illumination alternately to 100 lux, 500 lux and 1000 lux (probably still 2000) on a horizontal surface. For this purpose, the photometric head of the luxmeter was located perpendicular to the axis of the lamp.

Then, smartphones with various applications also became crazy so that the front camera and brightness sensor were located under the lamp. The sensor or front camera was located exactly at the point where the photometric head of the light meter was previously located.

All devices were located this way, with the exception of iPhone with the paid application “Luxmeter Pro Advanced” since this application for measuring illumination involves measuring light reflected from a surface. This application has quite a lot of settings including types of light sources, distance to the light source, etc.

Calibration is also possible when using some applications. Calibration was carried out in accordance with the instructions, namely 100LK.

Grade

During our test, we found that while calibration in some applications was possible to a certain value, it was not possible to set the value precisely enough. This happened because the step with which the value was set was large, or the value of 100 lux was not set at all, for example in the application LightMeter by whitegoods for iPhone 5, the calibration value was set to a maximum of 34 lux.

Deviations from the reference values ​​were sometimes quite high (up to 113% for the Samsung Galaxy S5 with the “Lux Light Meter” application from Geogreenapps). When setting the reference value to 500 lux, the smartphone display displayed a value of 1.063 lux. The lowest percentage deviation (3%) was recorded when using the iPhone 5 and the " LightMeter by whitegoods" . When setting the reference value to 500 lux, this smartphone showed 484 lux. However, we cannot conclude from this that this particular smartphone with a specific program will always show the correct value. When the illumination was set to 100 lux and the same application was used on the same smartphone, the deviation reached 89% and the device showed 11 lux.

We were able to identify a trend that the displayed values ​​on devices from Sony, Samsung and Nokia were significantly higher than the reference values, while, as a rule, IP hone the displayed values ​​are significantly lower than the reference values. Average deviation from the reference value measured in all applications on Android smartphones and Windows phones Phone , were on average 60% higher than the reference values.

Average deviation of all values ​​measured by different iPhone was 60% below the reference values. We also noticed that various applications installed on smartphones from Samsung and Sony showed similar values. Apparently, these models use a brightness sensor for measurement rather than a camera.

In some Samsung models, you can switch to the engineering menu mode by typing the combination *#0*# from the keyboard. By selecting the “Light sensor” menu item, you can find out the expected illumination without installing the application. So installing applications in this case will be unnecessary. However, all values ​​displayed by these devices also deviated from 37% to 113% from the reference value. Galactica Luxmeter" and "LightMeter by whitegoods " Unfortunately, disappointment awaited us here too. The chart shows that the four smartphones we tested showed completely different measurement results in some cases.

We suspect that the reason for these fluctuations is the use of different components, which the user does not notice in everyday use, but which becomes noticeable in direct comparison.

Is the trend in percentage deviations from the reference value maintained?

If you always use your smartphone with the same app, you can assume that you can make fairly accurate measurements if you already know the percentage deviation from the reference value.

But is the value by which the value deviates always the same percentage? To answer this question, 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 our black room. The brightness increment can be set very precisely by adjusting the distance between the light source and the receiver. An LED light source with a color temperature of 3000 K was again used as the radiation source.

In this test we looked at the readings of two different applications. Experience shows that application values ​​deviate from each other - in some cases up to 358% (values ​​range from 12 lux to 55 lux with a reference value of 100 lux), if we look at the percentage of deviations from the reference values, we will not see any pattern .

When using the application " Galactica Luxmeter" values ​​were higher180% of reference at 10 lux and 50% below reference at 10,000 lux.

When using the application " LightMeter by whitegoods » calibrated at 10 lux. With a reference value of 100, the deviation was 88% downward, and at 10,000 lux it was 59%. The values ​​of all the others attached were also significantly lower. For all other values, the readings were also lower.

Quite by accident, we discovered that measurements taken using the front and rear cameras show different values. In addition to this, some apps never show 0 lux even if no light is shining on the camera and it is covered with a cover.

Conclusion

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

In addition, the devices allow an assessment of illumination depending on the angle of incidence of the beam. Smartphones can't do either of these things, because otherwise they won't be able to perform their functions.

Although the developers claim that they can replace professional devices, since their applications have various smart functions such as calibration, but calibration does not allow you to set accurate values. And even if this is possible, then deviations in measurements still occur. Even when using the same application and identical smartphones, different measurement results are obtained.

Therefore, unfortunately, the applications are actually useless - even just to get a general idea of ​​\u200b\u200blighting.

from Thomas Pittner and Jaqueline Goldschmidtabout

LED lighting has firmly entered our lives, LED light bulbs are already sold even in grocery stores, and on the shelves of hardware and construction supermarkets there are even more LED lamps than conventional incandescent lamps and compact fluorescent (energy-saving) lamps combined.

Unfortunately, manufacturers often deceive customers by indicating on the packaging highly exaggerated luminous flux and incandescent lamp equivalent values. You buy a lamp that says "600 lumens, 60 W incandescent equivalent", bring it home, turn it on and realize that it is clearly dimmer than a 60 W incandescent lamp. Fortunately, according to consumer rights law, LED lamps can be returned to any store within 14 days (and to many hypermarkets within 30, 60 days and even a year). Returns are possible due to the fact that light bulbs (including LEDs) are still not considered a complex technical product.

In order to understand how much light a lamp actually gives, you need to measure its luminous flux. Typically, expensive laboratory equipment (goniophotometers, measuring integrating spheres) that cost tens of thousands of dollars is used to measure luminous flux (the total amount of light that a lamp produces). I propose a method that allows you to accurately measure the luminous flux of a lamp, spending only 87 rubles.

The main problem when measuring luminous flux is the unevenness of light brightness in different directions for different types of lamps. Some lamps shine more forward, some shine more to the sides, some shine almost evenly in all directions.

To measure, you need to somehow get the average brightness of the lamp. Typically, this is done by placing the lamp inside an integrating sphere coated with an ultra-white matte barium sulfate paint. The light is repeatedly reflected from the walls and hits the sensor. The goniophotometer rotates the lamp in a horizontal plane, takes multiple brightness measurements at each point of rotation, and calculates the total amount of light the lamp produces. We'll do it easier.

We will need a lamp with a spherical matte plastic cap. This matte cap will average the brightness of the lamp radiation in different directions. Such a lamp can be bought for 87 rubles in Leroy Merlin stores. In the picture there is another lamp with a glass shade - don’t pay attention: the stores themselves have what you need.

The exact name of the lamp is “Lamp NBB-60 (straight base) plastic ball, white”, manufactured by Axioma LLC, Moscow.

Almost any Android smartphone can be used as a brightness meter (lux meter). Most smartphones have a light sensor (located above the screen) that is used to adjust the brightness of the screen depending on the ambient light.

There are many light meter programs in the Play Market; I recommend installing a simple and convenient program Sensors Multitool. After starting the program, go to the Light tab and see the illumination value. The lux meter for all smartphones is not calibrated, and for different smartphones it will show completely different values, which may differ from the real ones by half, but this will not affect the accuracy of our measurements.

We fix the lamp on any surface (I used a piece of plywood). We attach the smartphone with two rubber bands to a package of milk or juice.

To measure we need a reference lamp. I recommend using the IKEA 600 Lm 303.059.76 LED1466G9 lamp. This lamp has a luminous flux that exactly matches the declared one, and very little variation in luminous flux between different copies.

Of course, you can use a regular incandescent lamp, but it is important to remember that, firstly, the luminous flux of incandescent lamps very much depends on the voltage in the network, and secondly, different copies of lamps produced by Russian and Belarusian factories can vary greatly in luminous flux. However, you can always find out whether an LED lamp produces more or less light compared to an incandescent lamp.

We tighten the lampshade, turn on the lamp, place the attached smartphone in front of the lamp, and launch the program. We calibrate our measurement system: we move the package with the attached smartphone so that the smartphone’s lux meter shows exactly 600 lux (if we have a 600 lm lamp as a standard). Now we unscrew the reference lamp and screw in the lamp that we want to check, without changing the distance between the lamp and the smartphone. The smartphone will show a value that will correspond to the luminous flux of the measured lamp.

I tested this simple measuring setup on seven lamps with a luminous flux from 200 to 1000 lm and two smartphones - Sony Z3 Dual and ZUK Z1. The measurement accuracy was 1-15%.

LED lamps have one feature - as they warm up, their luminous flux decreases by 11-12% within 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.

You can increase the measurement accuracy if you use any lux meter instead of a smartphone. Even the cheapest Chinese one will do, for $10. It may be poorly calibrated, but again this will not affect the accuracy of our measurements. It is better to warm up the reference lamp and those lamps whose luminous flux we want to measure for half an hour. The lux meter must also be firmly fixed and placed at such a distance from the lamp that it shows exactly as many lux as the lumens provided by the reference lamp.

I measured the luminous flux of the same seven lamps using a Lupine luxmeter-pulsemeter.

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

I note that all official accredited laboratories also have discrepancies in measurements. The picture below shows the results of measuring the luminous flux of the same lamp in 54 different laboratories. On average, the discrepancies were 3%, with a maximum of 26%.

This is how, “on my knees,” I managed to achieve measurement accuracy that not all laboratories can boast of.

Description

9Apps will provide free applications for Android. 30,000+ users downloaded the latest version of Lux Meter on 9Apps for free every week! Luckily, it's easy to get this popular app. This hot app was released on 2016-02-23. To get more information, you can come to our official website - 9Apps.
Lux Meter is a new Android based mobile application provided free of charge in the play store as a very useful tool. This application, when installed, can be used widely to measure illumination, like FC and Lux. this is done using an application through the light sensors in Mobile. This application uses the best of the mobile phone and allows you to measure in lux or FC and are linked. This Android phone based lux meter app is only designed to provide visual comfort to the user. Measuring light and its efficiency through a brief analysis in daylight, a simple android application is what's fun. Although there are various other apps, Lux Meter steals the show with amazing uses. If you are a company owner, this application will be an ideal choice. Simply download the Lux Meter App for Android and check the ideal light meter possible in your work space. This application will ideally guide you in the best way to take you to a better workplace environment for your employees. It helps in displaying the calibration factor preference, accurate and will be an ideal choice for any user. How to use the application: Given the use of this application, the way to use the lux meter is quite simple as well. all you need to do is connect to the play store immediately and download with a quick search for it. This app has a simple look promising to make the best use of it. select the location where you would like to check the lighting. just select the one you would like to check, this app also supports with min and max value as well. The yellow background of the application represents the illuminance itself, this value is given in bold, followed by the maximum illuminance value and the minimum value as well, one saved for quick access. This lux meter will give you the exact values ​​of all the above instantly. use the Counter Verification, which gives before and after along with the multiplier value. adjust light sources and get value instantly. reset the value as needed. Features and Benefits: This application is absolutely free, just connect to the play store and start downloading. It's bug free. It has built-in multiplier correction. supports luxury widely. supports the legs of the candle. The user interface is very friendly. consumes less memory, it requires Android 2.1+. The measure varies depending on the device. use it across the entire spectrum. A good range promises enough. Convenient navigation. Testing on bicycle and car lights is easy. records meanings easily. do not consume more data. There are countless unnecessary applications in our mobile, this application will not fall under their list. Installing and getting more benefit from it.illuminance is the key these days to make the best use of it and shine. measurements where and when required, stay enlightened with measure highlighting for life.

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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:

Name	Manufacturer	operating system	Calibration capability	Price
Galactica Luxmeter	Flint Soft Ltd.	iOS	No	-
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 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.