Too many variables. even when LED easily exceeded hps/cmh, you could still buy a turd LED that was over powering the diodes and relying on misinformation to sell their products.
Find any model that doesn't retardedly over power the diodes or COB LED and they are probably way better than hps/cmh bulbs.
So, before the lm301 hit the market. for sure, and likely before it's predecessor that was only 10-15% less efficient. Can't recall the model number.. LM351c?
hlg is overpriced. avoid them. Their pro-line (whatever their most expensive models are called) is comparable to the FC-XXXX series by mars. Huge price difference and virtually no quality difference. Just paying a shitload extra for a name unless they adjusted their bloated prices lately.
LED have probably been equal or better for at least 10 years at this point and much better the last 5-7 years. *not all options you could buy but the ones that weren't made like total shit.
Not so sure about those large 1-5w diode lights. think those were roughly the same efficacy as hps/cmh. The advancements after that were better than hps/cmh.
Even a LM301 based light can be a pile of shit if they overpower the diodes (skimp on diode count relative to watts). With the lm301, any light that is .20-.25watts/diode are the better ones assuming a decent heat sink and driver. This is diode-dependent. can't use that math for an LM561.. think those are rated for .5w on the samsung.com spec sheet. that samsung.com spec sheet is what matters. (or bridgelux etc..whatever the diode brand is, that's where the accurate info will be)
Also, QBs were poorly designed/thought out. It doesn't take advantage of the diodes and barely spreads them out. Bar style or anything that spreads the diodes out more is a far better option. QBs are a classic example of unimaginative engineers improperly or poorly employing new technology, in this case the small "midpower" diodes.
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light + co2 = yield. Doesn't matter much how those photons were produced.
Quality = genetics.
There is no polishing a turd for either of these aspects
ambient co2 will get you 50-60g/sq ft if you do things fairly well. Supplemented co2 might get you 20-30% more - must do things well in order to realize the most gain from ambient. That hasn't changed.