Glossary:
PAR (Photosynthetically Active Radiation):
PAR refers to the spectral range of light radiation within the visible range of light which supports photosynthesis, between 400 to 700 nanometers.
PPF (Photosynthetic Photon Flux):
PPF refers to the total amount of photons within the PAR range produced by a lighting fixture each second. This is expressed in micromoles per second (μmol/second).
PPFD (Photosynthetic Photon Flux Density):
PPFD is a measurement of usable photons which reaches one square meter of a given surface every second, and is measured in micromoles per square meter per second (μmol/m2/s). Whereas PPF is a measurement of the total amount of photons produced by a light, PPFD is essentially a spot measurement.
Efficacy (Photon Efficacy):
Efficacy is a measurement of how effective a grow light is at converting electrical energy into photosynthetically active radiation. This is calculated by taking the PPF value and dividing it by the measurement of wattage (Joules per second). Therefore, efficacy measures exactly how much usable light a fixture produces every second per watt used. (µmol/J)
