A reflected light meter with spot metering and incident light metering.
https://play.google.com/store/apps/details?id=com.willblaschko.android.lightmeterv2.free
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A reflected light meter with spot metering (using the device's camera) and an incident light meter (using the device's light sensor) in one app. Tested accurate against Gossen and Sekonic meters on most devices.
This is the free version of a paid app.
Email me if you have any issues or questions about usage.
Can be used for any type of camera from film SLR to pinhole to cinematographic.
In addition to the two meters, the app includes a Sunny Sixteen calculator and a Depth of Field calculator.