Discussing the electrical basics, the first parameter featured is the photosynthetic photon flux (PPF). PPF is the number of photons, measured in micromoles, within the PAR range (400 to 700 nm) that grow light produces per second (unit: µmol/s). The PPF is shown on the left side of the picture here. This is comparable to the luminous flux in human lighting. The second parameter is the photosynthetic photon flux density (PPFD). The PPFD is the amount of light (number of photons) within the PAR range that reaches a certain defined area of a plant canopy every second (unit: µmol/m²s). The PPFD is shown on the right side of the picture. This is comparable to the illuminance in human lighting.