Consisting of hand-held spectrometer-based Photosynthetically Active Radiation meter, Model BTS256-PAR provides PAR, illuminance, color, and spectral data to fully analyze any type of natural and artificial light source including SSL/LEDs employed in plant growth applications. Built-in electro-optical shutter for dark-signal compensation increases linear dynamic range of C-MOS diode array detector, while large area diffuser provides precise cosine corrected measurement geometry.