Light Meter is the best app for measuring light intensity. The app uses your device's light sensor to determine the intensity of light and shows it on a LUX Meter. It also can be used by photographers to test the light conditions for better results. The precision quality depends on the phone's light sensor quality.
Key Features:

★ Note what a huge difference there is in light between indoors and outdoors
★ Good and useful app to care for your vision
★ Very useful for a greenhouse
★ Use the app for indoor bonsai gardening
★ Understand what light bulbs to install at home
★ Helpful when relighting kitchen, office and rooms
★ Read the brightness of the sky, walls or bright objects
★ High accuracy light measurement
★ shows the sensor data
★ 100% free

Further this application provides you the ability to use flash light outside the application you can allow the services and permissions from the app.