To be fair, it is not All the LED Guys, and it is not them. The indoor gardening sector itself has perpetuated these myths from ignorance. It’s easy to believe facts about LED grow lights when the identical message comes from multiple trusted sources, including the vendors and magazines that serve the hydroponics industry.
What do you say we float some of these myths?
Myth 1: Lumens = Photosynthesis
Silly grower… lumens are for humans That lumens are an acceptable method to measure light generated by a grow light is your all-time number-one indoor gardening myth. Measuring light meant for photosynthesis in lumens is plain dumb. Let us be clear: a lumen scientific symbol: lm is a measurement of how much light the human eye perceives.
Plants and people evolved under the same light, coming from sunlight. But humans and plants utilize this light quite differently. Humans use the majority of the visible light range between 400nm and 700nm, but our eyes are focused on 500-600nm, mostly the yellow and green parts of the spectrum. Plants have an entirely different reaction to light, focusing their absorption around 400nm-500nm blue and 600nm-700nm red. They also absorb any light in the remainder of the visible spectrum in addition to non-visible light from the ultraviolet and infrared bands.
Measuring grow light output in lumens is an artifact of the lighting sector itself. Since light bulb manufacturers concentrate mainly on illumination for people, they print their lamp specifications in lumens. Some countries need light bulbs to rated based on lumen lighting. Indoor gardeners have adopted this way of measuring the brightness of the grow lights as it is generally accessible from the lamp manufacturers at least up until LEDs arrived to the scene.
When it comes to garden lighting, it is time to stop thinking in lumens and start considering photosynthetic photon flux density PPFD, which describes the density of photons reaching a specific surface area. PPFD is measured in micromoles mol per meter2 each second that is a more useful measurement for the light that your plants get than lumens. You require a quantum flux meter to measure how much photo synthetically active light energy is in fact reaching your plants. When analyzing LED grow lights, be certain that you choose a quantum flux meter that is specifically intended for LEDs, or your measurements will be off. Unfortunately, these devices are extremely expensive.