What is PAR, PPF and PPFD for growing plants with LED Grow Lights?


PAR – Photosynthetically Active Radiation are the wavelengths of light within the visible range of 400 to 700 nanometers (nm) that are critical for photosynthesis. PAR is typically measured as Photosynthetic Photon Flux Density (PPFD) which has units of μMol/m2/s. (micromoles per meter squared per second). Although PAR covers all of the colors of visible light, PAR is most effective in the blue, violet and red portions of the visible light spectrum, with secondary peaks in the yellow and orange portions. It is important to note that although ultraviolet (UV) and infrared (IR) are outside the visible range of light and not measured by PAR, these wavelengths of light play a critical role in increased trichome formation and cell quality.

Although PAR is an excellent metric for measuring the growing strength of an LED light, it is not the only metric for measuring how well a grow light will perform in growing healthy, robust plants. Other critical factors are the diode formulation, diode chip size, diode density and the power draw of the light.

PPFD – Photosynthetic Photon Flux Density μMol/m2/s.  PPFD measures the amount of PAR light (photons) that arrive to the plant’s surface each second. The PPFD is measured at various distances with a Full-spectrum Quantum Sensor, also known as a PAR meter. Natural sunlight has a PAR value of 900-1500μMol/m2/s when the sun is directly overhead. For a grow light to be effective, it will have PAR values of 500-1500 μMol/m2/s.

PPF – Photosynthetic Photon Flux μMol/s.  PPF measures the total amount of PAR that is produced by a lighting system each second. Although PPF does not tell how many of the light photons land on the plant, it is an important metric for lighting efficiency.