Humans and many other creatures perceive light differently than plants. The eye is differently sensitive to visible radiation depending on the wavelength. In daytime or photopic vision, the light sensitivity curve V (ʎ) applies, which has its maximum at 555 nm (yellow-green). All photometric measures, which include lumens, lux and cd / m², take into account this property.
Illuminance or luminance meters underestimate blue (400-500 nm) and red (600-700 nm) light due to the reduced light sensitivity of humans in these areas. However, plants use blue and red light intensively for photosynthesis. Instead of the inappropriate photometric measures, the photosynthetic photon flux density PPFD is used in the assessment of horticulture lighting.
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Measuring instrument: MAVOSPEC BASE