LED lights -- dimming vs lowering

[briefbriefs]

Hi! I'm running an HLG 225 QB in a 2x2x7 tent and was wondering what the thoughts were on dimming your LED's vs raising and lowering them? What are the benefits of each? What are the drawbacks? I can dim my lights and stay at within an appropriate lux level, so technically i could have them 12" from the plant without burning it. There have been studies done that say if you dim LED's then you're changing the light spectrum and not getting the full effect, but HLG conducted a study on their lights and said unless you dim it to 10%, there is no real difference in spectrum.
So. My question is... should i have my light running at 90% at 40" from my plant (im aiming for giving her 18k lux), OR.. should i dim my lights to 40% and bring them to 30" from my plant?

 

[tip]

I can't say for sure because I don't use that light but one way is going to cost you twice as much as the other. Ask yourself why the light has a dimmer included. You're lucky you have so much height to grow with. I don't have that choice in my tent.

 

[briefbriefs]

I can't say for sure because I don't use that light but one way is going to cost you twice as much as the other. Ask yourself why the light has a dimmer included. You're lucky you have so much height to grow with. I don't have that choice in my tent.

you're so right about the cost. That's definitely part of the appeal of keeping it dim. On the other hand -- i have trouble keeping my tent at the preferred temp, so when its at a higher wattage, it helps keep my tent warm and i dont have to run the heater. Its really crazy how much of a balancing act all of the variables are.

 

[parsing_trees]

Hi! I'm running an HLG 225 QB in a 2x2x7 tent and was wondering what the thoughts were on dimming your LED's vs raising and lowering them? What are the benefits of each? What are the drawbacks? I can dim my lights and stay at within an appropriate lux level, so technically i could have them 12" from the plant without burning it.

I tried dimming it to what seemed like an appropriate light level and kept it about 16" away and got light stress. I've had better results with the light at least 18-20" away, even at the same lux level. I don't know if 30" vs. 40" would make that much difference, though.

 

[briefbriefs]

I tried dimming it to what seemed like an appropriate light level and kept it about 16" away and got light stress. I've had better results with the light at least 18-20" away, even at the same lux level. I don't know if 30" vs. 40" would make that much difference, though.

hmm interesting! the more people i talk to, the more it seems that its not an "either, or" thing -- but more of a combination of the two. In a perfect world, you would have the light both at the recommended LED height as well as dimmed to the recommended lux/ppfd levels! Maybe its not just light intensity, but also the distance that photons travel that affects the plant's growth.

 

[Belle]

Still trying to figure out the settings for my hlg 600h. I stunted my first run I'm finishing up right now. I think I had it turned up too high and too close. Really wish I could afford a par meter.

 

[briefbriefs]

Still trying to figure out the settings for my hlg 600h. I stunted my first run I'm finishing up right now. I think I had it turned up too high and too close. Really wish I could afford a par meter.

damn that really sucks =\ but hey...its only through mistakes that we learn. And you dont need a par meter! Get a lux meter. I found one on amazon for $30. The recommended lux levels for LEDs are:
Seedling = 5k - 15k
Establishment (as they get their first true fan leaves) = 20k-25k
Veg = 25k - 30k
Early flower/Stretch = 35k
Flower = 45.5k-63.5k

Some strains will be more light sensitive than others, but this is a good starting point. Also, an investment in a laser thermometer (again, on Amazon ) is a great idea because while your environmental levels could be dialed in, your leaf surface temps could be way off. They've been a little hard to find because people are fucking morons and are buying these to take people's temperatures even though it very clearly says not for human use. But the link above should still have them.

Here are the LST (leaf surface temperature) recommended values:
80F - 86F (85F is optimal if you can keep relative humidity between 65%-75%)

 

[BII]

... On the other hand -- i have trouble keeping my tent at the preferred temp, so when its at a higher wattage, it helps keep my tent warm and i dont have to run the heater. Its really crazy how much of a balancing act all of the variables are.

You appear to have another problem. As you describe it, you have no tent temperature control. I suggest run your exhaust fan off a thermostat switch/outlet, such as I use a Lux Win100.

 

[briefbriefs]

You appear to have another problem. As you describe it, you have no tent temperature control. I suggest run your exhaust fan off a thermostat switch/outlet, such as I use a Lux Win100.

oh i got that goin! i have a inkbird keeping my temp at 78 and my humidity at 67%. It runs my inline exhaust fan when it gets too hot (which is why i prefer to have the tent too hot rather than too cold) and turns my humidifier on/off.

 

[Belle]

damn that really sucks =\ but hey...its only through mistakes that we learn. And you dont need a par meter! Get a lux meter. I found one on amazon for $30. The recommended lux levels for LEDs are:
Seedling = 5k - 15k
Establishment (as they get their first true fan leaves) = 20k-25k
Veg = 25k - 30k
Early flower/Stretch = 35k
Flower = 45.5k-63.5k

Some strains will be more light sensitive than others, but this is a good starting point. Also, an investment in a laser thermometer (again, on Amazon ) is a great idea because while your environmental levels could be dialed in, your leaf surface temps could be way off. They've been a little hard to find because people are fucking morons and are buying these to take people's temperatures even though it very clearly says not for human use. But the link above should still have them.

Here are the LST (leaf surface temperature) recommended values:
80F - 86F (85F is optimal if you can keep relative humidity between 65%-75%)

Oh, awesome. I'll look into it. Thanks so much!

Ordered.