I find the philips site a guiding light. They go off teaming up with commercial growers, using their own lighting knowledge, and the growers plant knowledge, to do trials that lead the industry. I will read any of their case studies, but tomato one's are especially close to our own goals. They will side-light, top-light, inter-light and base-light. Find what's best, and offer a commercial product that works. The scale of investment and the brains involved is right up there.
I give you the future. An illuminated scrog net
There is little doubt that for close up lighting, led's are the 'goto' choice in industry. It's just so damn messy though. Side-lighting works, but it's just in the way. Overhead works, but constant canopy adjustments, and again the clutter, is high maintenance. This is why commercial tomato growth is using interlighting and high bays. Not that high bays are specifically more efficient. They are low maintenance and very powerful.
Micro-grow users are shunning the big lights now, and getting right in there with pin point accuracy LED lighting. While people with a warehouse full, don't have time.
Vert growers obviously use side-lighting, but instead of overhead. It's rare we see a side lit crop using top lights as the primaries. To date, I have seen nobody(else) use inter-lighting or uplighters.
Led's are no doubt taking over. Anyone uncertain can look in the microgrow diaries section. Where the highest gram per watt claims are being made, using less watts and less efficient light(compared to a 600). It seems like placement is really helping. Now we have Samsung offering near 200 lumens per watt, even the impressive efforts over there must be rather outdated. There is a move towards making big led lights though, and hanging them high like hids. Which will replace hids, but is a slightly backwards step for a microgrower.
I want that led net. Using the 40w per foot guidance that most are happy with, they're talking 4300lumens. In 200lm/w leds, that's 22w per foot. If I put 3 nets, 3" apart, that's aiming to light 9" of canopy depth. If each is a 3" squares net, with a 0.5w led at each junction, That's 24w per foot. Interlighting. So we can still grow up another ~8" which top lighting can take care of. I have never done the math before, and I'm unsure how hot a diode will get with 0.4w of heat dissipation. We don't need leds every 3" though, we could have string that's linearly lit.
Perhaps I should make it.