In the video we mention that while different manufacturers have varying recommended heights from canopy, we tested them all from the same distance to give a true apples to apples comparison. As you bring any fixture closer to the plants, or the measuring device, the PPFD will increase proportionally. You would therefore see the same comparative results from any distance. Testing at further distances provides a simple way to simulate canopy penetration. By taking measurements at these distances, it is plain to see how quickly the intensity of most brands dissipates. This has HUGE implications for under canopy growth and the elimination of LARF, which is a problem with many fixtures out there. Kind LED's focused lenses magnify the intensity and allow for far superior under-canopy development.