You must have seen professional photographers measuring the light levels whenever they proceed to photo sessions. Depending on the intensity of the light measured by their light meter devices, photographers tend to increase or decrease the lighting for the photo session to begin.
If you forgot your light meter device at home and want to check the light levels, then you can use a light meter app called Light Meter. It is developed by Trajkovski Labs and can measure the intensity of the light in terms of Lux unit.
It uses the light sensor of your smartphone to measure the light levels. This light sensor is usually located near the front camera of your smartphone. This is why it works better if you to turn the front side of your smartphone towards the light source or the lit area.
In the Light Meter app, you will find the old fashioned analog meter in which a needle moves on the circular scale to show you the reading. This type of meters were common in the old times but now digital meters have replaced them. Having such a meter might give some of us a nostalgic feeling of working on the old Physics laboratories.
As we move around with this app running on the smartphone, the app displays the moving needle in the meter and its reading in terms of Lux units. In addition, it also displays what the light levels usually correspond to such as street light, room light, office light, daylight, candle light and so on.
Furthermore, Light Meter also displays the light color value in terms of the Kelvin units. For this to work, your device should also have another sensor called the color sensor. This might not be available in all the Android mobile phones.
You can get the Light Meter app from https://play.google.com/store/apps/details?id=com.bti.lightMeter.