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As an updated version of Grove - Light Sensor 1.0, the Grove - Light Sensor v1.2 is also aimed at measuring light levels, however with higher reliability and sensibility.
It is an analog module and output various electrical signals which can be converted to different ranges (It depends on the Analog-to-Digital-Converter on your controller board. For example, it can output 0-255 for an 8-bit ADC). It integrates a high-sensitive and reliable phototriode, and just like other grove modules, it is interfaced with Grove port which can save you a lot work in wiring.