GroErr
Well-Known Member
Yeah definitely a lot of factors. For the record I've been running between 16-18" above canopy since I put them in and I don't see any need to place them lower. Besides losing coverage as you get closer to the canopy, I'm getting solid buds as far as 30" down the plants, why would I want or need to go closer and lose coverage? Even at the 18" height I noticed a couple of phenos this round getting what looks to be bleaching on a couple on the top layer only.That is awesome information. I've seen people (well, online...) pound their spaces with 60+w/sf, and others go as low as 25-30w/sf.... and I've seen great results from both! I haven't comprehensively gathered the rest of the picture: who is using soil vs. hydro, what nutes and how much, etc. -- and how far from the canopy are the lights hung. There are so many variables that its hard to convey what works and what doesn't just in terms of one element like w/sf.
Every time I lower my lights I get nute issues, so my hypothesis is that tons of light stresses the plants, and unless the grower can match nutes to that extra demand, it works against the plants. In my 2x4 I'm running 8 3070's at about 50w each for 50w/sf, but I have them about 26" off the canopy (which is twice as far as I've seen others go). With no lenses or reflectors, if I had dimmers on them all I could probably dim them and drop them significantly and run the tent cooler. Next rebuild maybe.
In my 3x3 as I mentioned I'm experimenting with an HID/COB mix, so I'm not sure how to calculate the w/sf. Your method of oz/per gallon of medium is an interesting constant in the comparisons, especially as we compare different light platforms.
I don't see the benefit of switching to an efficient light source then running w/sq./ft that would equal a hid/hps setup, just doesn't seem like progress and probably a waste of money/light. Based on the runs I've done, 30w/sq./ft seems to me like a decent balance, at that rate you could probably go even higher above canopy and be fine to stretch your coverage a bit.
The oz. per gallon of medium is just kind of an internal reference I use to track how the same pheno does under different conditions. In this case lighting changes as it's about the only significant environmental factor that changed over the last few runs. Of course the key is a constant like my medium, it's always been 50% triple mix soil/50% Pro-Mix so I can rely on that factor to be the constant while changing out other environmental factors and get a relatively accurate read on the effects.