I downloaded a free light lux meter on my android phone. This thing is pretty cool and can be a nice gauge to help you determine how much light your giving your plants. As you can see here, my peak or max lux was 68,982. This was when I tested full power at about 6 inches away from the light. As cannabis growers we care more about PPFD than we do lux, and while it's not possible to convert between the two, knowing the spectrum of our light, we can use a calculator to get a rough approximation.
Using this converter here we can select our light spectrum and input our lux to get an idea of where our PPFD is at. This tells me my light running at 100% 6 inches from the canopy is going to give my plants way more light than they can handle. Flowering plants want to be in the 800-1200 range, depending on a number of factors, including whether co2 supplementation is used.
You want your veg plants in the 300-600 range. So knowing that I tested my light at 18 inches at 80% power, which is where I had it while getting the light stress. The center measured 51k lux which converts to 1310 umol/s/m2 and off to the sides it went down to about 40k lux which converted to
1027 umol/s/m2, both way more than veg wants.
It's nice to have found the problem, verified it through seeing the plants react positively to the changes, and then verify it further using tools to measure light levels. My veg tent was at about 20k lux in the center so I dropped it down to 15k lux in the center, around 13k where the main tops are, which converts to 333 umol/s/m2. They were up over 500 before the change, so I am curious to see if this helps them increase their perk going into the end of the day.
