Luminosity / Lux / Light TSL2561 Digital Sensor Breakout
The TSL2561 luminosity sensor is accurate in calculating for Lux comparing with low-cost CdS cells. It can be configured for different timing ranges to detect light up to 0.1 to 40,000+ Lux.
This sensor can measure infrared, full-spectrum, or human-visible light. It could be easily interfaced with your Arduino since it uses I2C. By accessing the three addresses, you can have three sensors at the same time. It is excellent for low-power devices since the current draw is low.