En substance, lumens are a human perception-based unit of brightness measurement. Different from humans, plantes « perceive » light in different ways. The light necessary for photosynthesis may not always be bright.
Il’s time to move on from lumens to a concept called « Light Quantum Flux Density » (PPFD), which represents the density of photons that arrive at a certain area.
To find out how much light energy is used for photosynthetic processes in your plant, you need a quantum flux meter. Make sure you select a quantum flux meter made especially for LEDs while testing LED grow lights, or your measurement may be blocked. Sadly, the cost of these gadgets is rather high.
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