Hydrofarm LG17010 is a precision instrument used to measure luminance, which is a measure of the intensity of light. It has a fully cosine corrected sensor for the angular incidence of light, meaning that it will accurately read the light even if the sensor is not held perfectly perpendicular to the light source. The sensor is made of a stable, long-life silicon photo diode. The meter accurately measures to 400,000 LUX (40,000 FC) and has auto-ranging scales. You'll appreciate the digital light meter's ultra low power consumption and ability to save up to 50 measurements for review.