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The reason lights need distance is so they can spread the light uniformly over the area that you want to light up. Uniformity of light distribution over a certain area is the only reason to hang the light at a certain height. This is a constant related to the size of the area and spread of the...

I have never seen them use a camera for that. Still the point is that when you use a phone to measure light uniformity, you will see large difference over the surface. I also used a phone and noticed that the light uniformity did not match at all with what I calculated. So I ordered a cheap lux...

That's why I like to divide: 3000K - Lux / 43 = PAR 3500K - Lux / 45 = PAR 4000K - Lux / 42 = PAR Less typing and easier to remember. To be honest you might as well divide by 44 (as an average) since it doesn't matter all that much anyway because these things are massively inaccurate

Lux meters in phones are pretty much useless though. They are very direction dependent. If the light comes under an angle the intensity is measured much lower than it should be. Lux meters with these white diffusion caps are much less sensitive to incident angles. Plus the phone sensors are not...

Did you actually watch the video that you posted? They show an SPD with a huge amount of UV.

Yeah those sensors work great. I have them on the outside of a plastic container though. Not sure if they will make it through 2" of wood. Also work well in detecting that water is actually flowing through the distribution line (to see if the pump is actually working when it's supposed to be "on")

That's the laws of thermodynamics in action yes.

veg duration is irrelevant to yield. It's only relevant to reduce plant count. Lots of plants per m2=short veg. Few plants per m2=long veg. Yield will be the same.

If it's not (fully) used it simply warms the plant up. Absorptance and photosynthetic efficiency are different metrics. Both charts were posted in that thread. The Absorptance chart was posted already earlier and this is the RQE chart (adjusted for absorptance) for Cannabis that was presented:

Bugbee did some tests and he saw that greens would benefit from more blue in the spectrum (something like 10% more yield). Whereas flowering/fruit bearing plants would yield much better (up to 25% more yield) with less blue in the spectrum. So spectrum does matter indeed. That PowerVEG light...

You are confusing absorption with photosynthetic efficiency.

Yeah wouldn't go lower than 8" myself with 8 bars distributed over 5'. I hang my strips at 6" (equal to heart-to-heart strip distance). Sometimes I let the taller plants grow between the strips. No CO2 at all. It's not that big a deal I guess. I see about 1% to 2% more light in total per inch...

You can go much lower really. With a strip light the minimum height you can use is equal to the heart-to-heart distance between the bars/strips

Gavita is better when you want to keep the light closer to the plants which is possible because of the better spread. Then you would lose a lot less light on the walls. Boards are more for when you have a huge space and losing light on the walls isn't so much of an issue.

It's true though. Doesn't so much matter which type of light perhaps, but people tend to run higher intensity with leds.

Strips give you better spread and lower cost.

If you spread 100 diodes uniformly over a 2'x2' space then each diode would only have to illuminate a 2.4"x2.4" square. So it would actually do that from 1.7" up already. Radius = sqrt(1.2^2 + 1.2^2). For a 120 beam angle the led achieves uniformity when the height is at or greater than the...

Yes , he agrees that we need to spread the light sources. He just doesn't want to admit that another product but his own can achieve that better at the same component count (and then still cheaper). Why not use strips with 144 diodes? You'd need only 2 strips per board? That's already killing...

But inverse square law has nothing to do with light penetration. I know GrowLightBullshit or one of his many other nicks that got booted off the forum was always proposing this idea, but it's simply not true. The reason he saw more penetration in his chart with the light very high is because if...

Another amazing led strip light hits the "stores". I'm a bit baffled by his claim that it's slim-line and therefore good for multi-tier grows though. His hanging system doesn't really seem to support that use case. But then maybe he has other hanging options besides hanging it on the power cables.