Do you know of a difference between quantum board light height and power level?

[the123321]

I have a 240w kingbrite quantum board. I have a lux meter and if I get the same lux at for example 36" from plants with the power on 80% would there be a difference if the lux is the same at 24" and 60% power? If the lux is the same is there a difference in having the quantum board higher up in the the tent at a higher power level vs at a lower height at a lower power level on there?

 

[4d-Rock]

Not an expert Here, but If your readings are the same then there wouldn’t be a difference at those two spots. However, the higher the light, the more spread you have, The lower it is, the less area the light covers. so I guess it depends on what kind of foodprint you are trying to cover.

 

[Simplicio]

The real question is how much light is wasted.
Assuming about 140 watts of real light power from the 240 watt light (60% LED efficiency),
Full power = 140 watts bearing down on the canopy
60% power = 84 watts bearing down on the canopy
How much of that extra 56 watts is wasted?
My guess is that at least half gets used.

I run mine at full power high up.
The underneath plant parts get much more light this way.

 

[the123321]

Thanks. I plan to try the light on the lower power lower to the plants in the tent on there.

 

[Olderfart]

Thanks. I plan to try the light on the lower power lower to the plants in the tent on there.

As Simplicio mentioned, you get more light to the lower parts of the plant if you turn the lights up and move them farther away from the plant.

For trivial example, if the light is a foot away from the top of the plant, and the plant is a foot deep, the light getting to the lower part of the plant will be ~~1/4 of what the top gets. If the top of the same plant gets the same amount of light from a brighter light four feet away, the lower part of the plant will get ~~>1/2 the light at the top, or more than twice what the lower part would get from a closer light. This is for leaves with direct light on them, I am not talking about light that goes through the upper leaves. The real numbers are more complicated due to wall reflectance and other stuff, but you get the idea. Brighter light further away delivers more light to the lower canopy if you can deliver the light needed. This is often referred, I think misleadingly, as penetration, but it has nothing to do with penetrating anything, it is just the way light drops off with distance from the source. If you want to get technical about it, google inverse square law.

Another way to look at it is that in sunlight, every exposed leaf gets the same light intensity no matter how tall the plant. Since the sun is so far away, light intensity does not vary over the comparatively tiny distances involved in plant size.

Happy growing.

 

[4d-Rock]

Myself I’ve had some trouble dialing in my Quantum board height.

I have a 135W HLG QB288 v2 in a shorter tent which may be the problem. I can’t seem to use it at full power and have all my plants all nice and flat leafed. right now I have two plants, one of which is shorter and perfectly fine, the other one at 18” from the light has all the serrations pointing up. I’ve dialed down the power but I want to slowly bring it up so that the yield at the end isn’t Affected too bad.

I think the solution for me really is to get a taller tent.

Added some pics below Of curled tips vs one that Is fine

 

[the123321]

Thanks. The information about the difference in the light it gets at different height does help with it. I have a 32x32 tent with the 240w kingbrite quantum board led that I have the two heat sinks in a sort of square shape in the middle of the tent. I am going to try having the light at like 80 - 90% power though at a lower height to get the light at the tops of the plants without turning the light all the way to 100% on there.

 

[BII]

Regarding @4d-Rock stating "I think the solution for me really is to get a taller tent," another solution is just to raise the shorter plant, put something under it, so the canopy is at the same level - then adjust the intensity up/down.