LightSpectrum Pro: Measure color temperature and color spectrum with the iPhone

LightSpectrum Pro: Measure color temperature with the iPhone

I just got that earlier Test report on the LED tea lights completed and stumbled upon the color temperature measurement. A customer stated the color temperature of the LED candles as 2900 Kelvin and I felt the need to check this value. A little search in the App Store brought me to the app "LightSpectrum Pro", which should be suitable for measuring both the color temperature and the color spectrum. The app runs on iPhone and iPad, but my test was made with the iPhone XS.

Color temperature: not super accurate, but quite good

The app analyzes the information it captures via the iPhone camera. This is of course not a calibrated device for measuring the color spectrum and temperature, so you shouldn't expect miracles here. I therefore use the iPhone app rather out of interest to see which region we are in. You probably won't get 100% binding results this way, because sets like this are not for nothing Lighting Navigator, which consist of a sensor and a stand-alone app and cost just under EUR 800. If the company provides me with a set, I'll be happy to write a report about it, but now let's take a closer look at the "LightSpectrum Pro" app. ;-)

On Youtube I was able to find a video of Admando Ferreira who took the trouble to compare the values ​​of LightSpectrum Pro with the values ​​measured by his Canon camera. Canon does a pretty good job with the automatic white balance and for this reason the values ​​displayed by the camera should be quite realistic. In its tests, LightSpectrum Pro is at most about 150 Kelvin off, which is actually quite decent accuracy for an app that does not cost 5 euros.

The two screenshots are from the above video and show that the LightSpectrum Pro app is quite close to the measurement of the Canon camera.

The two screenshots are from the above video and show that the LightSpectrum Pro app is quite close to the measurement of the Canon camera.

Areas of application for color temperature measurement

As far as I have read, the measurement of the color temperature is mainly used when filming or taking photos to set the white balance. With photography in RAW, however, this is superfluous, since the white balance is carried out later in the program. In the case of videos, on the other hand, it may make sense not to film in log format.

Another area of ​​application is probably lighting planning, in which the color temperature is important as it has a strong influence on the human body. If you haven't heard of it yet, you are welcome to take a short detour into the article "Blue light filter" do.

I have to admit that I have little idea about all this film and photo stuff and that's why I approach the app as a layman. I have that too Message read through by the filmmaker Adam Plowden, but this one is relatively superficial and says only this much:

"As a filmmaker you can use the app to get a rough impression of the lighting conditions, but if you adjust the camera and notice that it doesn't look right, then you should trust your feelings more than the app."

In the first screenshot you can see the menu options on the right, with which you can display different evaluations. Two examples of this can be seen on the screenshots on the right.

In the first screenshot you can see the menu options on the right, with which you can display different evaluations. Two examples of this can be seen on the screenshots on the right.

My tests with the app

To see how the app behaves, I just tried different lamps that have a different light spectrum. These were, for example, the LED tea lights, a black light lamp and an LED flashlight that can emit both red light and white light. The results that I measured all looked very plausible. Above all, you can see very well that the black light flashlight, for example, has a very strong deflection at a certain wavelength range. On the other hand, I was a bit surprised by the evaluation of the real tea light, which shows some peaks that I cannot fully explain ... but I'm not a spectrologist either. ;-)

In these screenshots you can see the evaluation of the UV lamp (black light), the electric tea light and the real tea light.

In these screenshots you can see the evaluation of the UV lamp (black light), the electric tea light and the real tea light.

In the app itself, you can activate various graphic evaluations, which evaluate the light conditions captured via the camera image in different ways. There is an evaluation with a pie chart that shows the distribution of the wavelengths and color ranges. You can also show a kind of bar chart that shows which wavelengths occur with which frequency. Both very interesting additional features to the main feature of the app, which is actually the color temperature measurement.

In addition to the various diagrams, you can also save images and evaluations as screenshots in the app. These can be named and can be called up again at any time via the.

In addition to the various diagrams, you can also save images and evaluations as screenshots in the app. These can be named and can be called up again at any time via the.

When I tried it out, I noticed with the app that it sometimes goes into a state in which it still updates the display and the values, but then it somehow "picks up" in a rough Kelvin range. An example: I measure the color temperature of the LED tea lights under a black ceiling and get 3600k displayed. Then I move the iPhone briefly to the daylight and the display jumps to about 5000k, but does not go back to 3600k when I move the iPhone back under the ceiling. The values ​​still jump back and forth slightly, which shows that the LightSpectrum Pro is still updating the evaluations, but the values ​​no longer seem to be plausible.

In this case I just shot down and restarted the app and got "normal" values ​​again. So a bit of "caution" is called for when you have highly variable lighting conditions.

Measure light emission

The specific light emission in lx (lux) can also be measured with the app. I didn't quite understand what the difference between this value and the light intensity is, but that Wikipedia article for "Lux" shows that there are two different physical units here. The app does not show the light intensity but the "specific light emission", which is also abbreviated with the SI unit.

In some cases the camera image is blurred. However, this is irrelevant for measuring the color temperature. I assume the bug will be fixed soon.

In some cases the camera image is blurred. However, this is irrelevant for measuring the color temperature. I assume that this may even be intentional so that the displayed writing is easier to read.

Summary

My conclusion is that the app is a nice and interesting gimmick with which you can evaluate various light spectra and color temperatures. The results are understandable, but I cannot say how close they are to the results of "real" measuring devices. For my hobby area as a blogger, the whole thing is absolutely sufficient and a nice thing for the little money, because of course I would never spend 800 euros on a real measuring system. So the question is simple: do I get the app for EUR 2,50 or nothing.

If you are curious and like to play around with such apps, you can take a look at LightSpectrum Pro. You can't go wrong with the price. And since the last update of the app was only a few weeks ago, it is apparently also being actively developed and adapted to new iPhones.

[appbox appstore id468368751]

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