Android phone has a light (illuminate) sensor.
This sensor is visible on the face of the android device.
So you can easily use it. Just take your phone near it close to the light.
This awesome lux meter app reports its values in lux value, and has a typical dynamic range between 1 and 30,000 lux level.

***Features***
- Direct reading in lux.
- Support maximum and minimum lux values.
- Make awesome graphical charts of Lux intensity.

- Guidance for recommended light level in different work spaces like rooms hotels offices museums and other residential areas.
- Custom calibration of light.
- Keep calibration factor in preference.

Note: Be aware that the accuracy of the light sensor vary between different devices and values shown in this application are indicative.