This is gonna be science against experience I suppos; I believe the height matters because:
- more height equals more coverage + blending, when the crafters say put it at X inches, is because they have measured the angles and determined that at X height, the mixing and coverage + PAR. The lowest the lamp, the highest the PAR but in a more concentrated space.
- a closed number as 12" is not accurate, it depends on the lamps design, positioning, plats layout and requirements of PAR across the canopy. If the lamp has lenses on top of the leds to widen the beams, that varies the band blending angles and thus the height. If your lamp has lenses, you could put it closer to the canopy while still getting a good blend of bands. If you put the lamp too close, you will get uneven growth.
- These lamps have generally 1-2 UV and IR leds, this means blending of those bands doesn't happen every 5-10 cms, they need some height in order to make those 2 bands beams expand and reach the total effective coverage area. UV is what makes resin btw, so it is more important during bloom.
I used to run a P150 at 12", it has lenses and as soon as I realized what I was doing, I moved it at 18" for the optimal range according to the factory, the growth got more even since then, and when it happens that some plants surpasses certain height and they get closer to it, I notice a yellowing in the middle of the canopy / coverage area, meaning the plant is concentrating its efforts in that area that has the most light and PAR.
