Unlike simpler sensors, the TSL2561 measures both infrared and visible light to better approximate the response of the human eye. And because the TSL2561 is an integrating sensor (it soaks up light for a predetermined amount of time), it is capable of measuring both small and large amounts of light by changing the integration time.
The TSL2561 is capable of direct I2C communication and is able to conduct specific light ranges from 0.1 - 40k+ Lux easily. Additionally, the TSL12561 contains two integrating analog-to-digital converters (ADC) that integrate currents from two photodiodes, simultaneously. Each breakout requires a supply voltage of 3V and a low supply current max of 0.6mA.