Someone in this thread said you would overdo the heat before the light. LMAO. Guy never saw light bleaching before apparently. I love the responses in here.
I have seen strain differences though. Some (only sativas) I have seen grow right up to the damn glass in the 1000w hood, and NOT be bleached. No bullshit. It was kinda in the corner but still. That plant pulled like 17 ounces I think. So some I do believe can handle just about whatever you throw at it light wise(rare, and dif stages of growth want dif strength). As far as commercial grows, someone said what I was going to already. You get tons of light coverage and crossed light patterns etc..
I said that in my original post. I've found that the runts tend to prefer less light and usually much less nutrients. I don't grow sativas so don't know about them but I;ve grown plenty of hybrids mostly indica dominant. Once when I planted 7 different seeds, 3 Iced Grapefruit by Female Seeds and 4 Purple Haze by G13 Labs. I found that 2 plants were bleaching and 5 were thriving. The light was a 600W MH about 8 inches above the plants by the time they were 10 days old.
So I lowered the height of the pots on those 2 plants to get them away from the light while keeping the other plants nice and close. The 2 plants that I moved away started looking much better after I moved them further from the light but in comparison to the other 5 they were truly runts. And it showed in the end product too, one of them yielded 5 grams!!!!? Can't believe I even let her finish, just too kind I guess. Each plant was in a 7 gallon pot. The other runt yielded like 35 grams. One of the good plants yielded over 8oz by itself!!!! It was a G13 Labs Purple Haze and had delicious and very dense buds.
And these were grown without supplementing co2. I've heard that when you supplement co2 they can use more light than normal. So anyway I've concluded that plants that like low light (and probably low nutes) are gonna grow more slowly and probably gonna end up yielding a little pile of low quality trash. Has been for me at least.
When I've grown outdoors I've found the exact same pattern. The plants that have shown signs of bleaching (rare case) I have taken them out of direct sun and placed them in some shade with my mint and rosemary plants (since I do know about bleaching) and they responded well. But the plants that remain thriving in the direct sunlight are the plants that are gonna be the good yielders with far better quality. And the longer the days the better they grow, they love those 17 hour days with clear skies.
And the thing (that I mention early in thread) about the sun is it provides waaayyy more light than any indoor setup does. The sun can provide over 1000W of LIGHT per square meter. And maintains well above 600W per square meter for great lengths of the day.
Put a 1000W hps in a square meter garden (which you can't do anyway due to heat not light) and you still don't even come close to the sun's light since the 1000W hps does NOT create 1000W of light. It makes about 800W of heat and 200W of light. That fact alone really shows that you'd be hard pressed to even come close to the sun's light intensity. And the fact that the HPS makes 20% light and 80% heat, that's 400% more heat than light, tells me that you would most likely overdo the heat before the light seeing as 400% is a lot and all.
That is in most cases, not for those plants wanna be shaded.
I think it makes perfect sense that the more vigorous plant is going to want more light.
And yeah the 1 time I used a cooled hood I too had the plants grow into the glass with absolutely no probelms. I don't use cooled hoods anymore though because the light distribution sucks and I was using a magnum XXXL. I swapped back to my large adjust a wings for good because the spread is that much better and the open bulb is also better to have for up to 10% more light and also more of the spectrum.