The Dude Grows Show

Why turn LED’s down?

I keep hearing advice about turning down your grow lights and then lowering them closer to the plants. What is the difference if I’m at 100% with lights 4 feet away from canopy at 400PPFD or if I’m at 50% with lights 2 feet away and still at 400PPFD? I like to keep my lights as high as possible in order to even out the footprint so the edges get almost as much light as the center. But if I’m missing something please educate me so I can do the best for my girls.


7 responses to “Why turn LED’s down?”

  1. J Mystro Avatar

    Internodal spacing will increase the further away the artificial light source is. Plants know. It’s a metric we can’t measure.

  2. Sunnyinbectopia Avatar

    If they look great at, whatever you’re doing, fuck yeah. If they don’t then do what is recommended. You don’t have to do anything you don’t want to do. It’s up to you how good your weed is to smoke.

  3. NayHay Avatar

    The way you’re doing it makes the lighting more even across the top of the canopy, from edge to edge. It also minimizes the difference between the light levels at the top of the canopy versus the lowest (unobstructed) part of canopy too. But you may be able to save a bit of electricity by lowering both the height and the light output, but lose lighting evenness.

    Also note the difference between 4 feet and 2 feet in lighting intensity is not 50%, it’s 75% (see the picture demonstrating the inverse square law: )

    1. Tent Drummer Avatar

      The energy savings is something I forgot to consider, good point. As far as my 4ft to 2ft example was just an example, I wasn’t trying to say that’s how the math works out. But I’m really now reconsidering my approach based on energy savings, thank you for that.

  4. RASUFA Avatar

    I turn my down and lower them because of excess heat. Plus there is less power consumption. True that you lose foot print but I actually like to keep my lights around 24” or less if I can.

  5. Tent Drummer Avatar

    Lowered them today! Right at 50% and my 2 new seedlings (Afghan Kush and Cement Shoes) in a 2×4 are getting 200 PPFD at 24″. I can just FEEL the savings. Thanks DGC

  6. PacNW Dan Avatar

    Remember watts = heat. Many of us turn down our lights because you can get the same effective coverage and PPFD if it’s closer, but with a lower wattage requirement and thus a cooler tent. If you’re going for efficiency, the goal is to get the most desirable PPFD using the lowest watts.

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