At certain parts of the specturm, the human eye cannot perceive light intensity changes once the light level exceeds a certain point. Too often this causes people to adjust their LED lights far past the ideal PAR level for their corals or plants. This usually results in burning, bleaching and/or death. With the PMK you can adjust your lights while monitoring exactly what light is affecting your corals and plants throughout the day. Also, not all corals are alike. Each type of coral has its own range of light intensity that makes it happy or not. The chart on the left shows this phenomenon without getting all technical.