Light distance at professional grow facilities

Discussion in 'Lighting' started by cannabineer, Apr 1, 2016.

  1. Hey people, I have done a ton of reading and general research when it comes to all aspects of indoor growing and I'm happy with most of my knowledge and beliefs but I have recently come across a contradiction. Here it is,

    I have always believed that it's best to keep your lights (MH and/or HPS) as close as possible (without heat stressing your plants). I have found that with good airflow, between canopy and bulb, as well as a fan pointed at the bulb itself allows the lights to be very close to the canopy, about 8-10 inches for a 600W MH and the leaf temp stays in perfect range around 78F.
    I have read in many places that this is ideal since having the lights closer to the plants means more intensity and deeper penetration. Given that the plants are at ideal temps this should be the best way to go unless the high light intensity is too much hence not optimal. Most setups that I've seen try to keep the lights as close as possible and they seem to do very well. I do understand that as plants get bigger you need to sacrifice intensity for coverage but let's just consider the stages where you can keep your light/s very close without worrying about coverage, i.e. early/mid veg.

    Here's the thing though, all the professional grow facilities that I have seen on videos that are in big warehouses with hundreds of plants, always keep the lights ridiculously far away from the plants, like 3 or 4 feet. And they do very very well. Why do they keep the lights so far away. I know that there are heaps of lights in these setups. Is this the reason why? So that the lights all create more coverage and they all sort of share the lights.

    So in a small setup with only 1 or 2 lights, should you keep the lights as close as possible or keep a good distance? I saw a video on youtube on the "Grow Boss" channel and he shows you a small single light setup (400W MH in veg) with the light not even close and he says its way too close and its harming the plants and making them "miniaturize", then he moves it up to about 2 feet and says this will solve the problem. Here's the video. Start at 4:20 and just watch for about a minute to see what I mean.


    This really made me wonder but I don't believe he is right. I have done a few grows in the past using 600W MH for veg and I kept the light nice and close like 8-10 inches with good air flow as I said earlier. I had very healthy fast growing bushy plants (nothing like the twig weeds in that video lmfao).
    I believe that the plants were able to utilize the high light intensity. Seeing this guy raise a 400W MH that far up trips me out, and he's saying that this is the key to making those shitty plants less shitty. It really makes me think that although he may be wrong, perhaps I am also wrong and the right answer is somewhere in between.

    My philosophy is that our beloved plants are able to soak up massive amounts of light and the more you can give them (within reason) without heat stressing them the better. Their philosophy is that HID lighting is ultra powerful so you need to tread with caution and keep the light a mile away.

    I've used a light meter to measure the sun on the middle of a clear summer day and it read over 120 000 lux. I used the same meter to measure a 600W MH from 8 inches and it was well under 100 000. Furthermore the sun gives the same light intensity to the top of a 300 ft tree as it does to the ground. So that is one very powerful light they have evolved with. I know that indoor lights are kept on for much longer and they don't vary with weather but still the sun is a fair bit more powerful than even a 1000W HID at 12 inches in terms of intensity, penetration and bandwidth and it contains much more high energy radiation such as UVB which is more harmful for living organisms.

    What do you guys think? I know that the professional warehouse grows have heaps of lights. Is this what justifies the lights being raised so high for them?
    And what about small setups what are your thoughts on that? Is it best to keep the lights as close as possible to get better penetration and higher intensity?

    Do you agree with the "Grow Boss" that its best to keep your light waaayyyyy above your plant, 2ft for a 400W MH and who knows how far up he would raise a 600W MH. Would you really keep your light that far away throughout veg? Wouldn't you get a lot more stretch and less vigorous growth?
    In my opinion, that light was too far away to begin with. Even if it was a 600W MH, (much hotter and brighter than a 400W MH) I would be moving that light down a few inches to try and get light intensity up closer to what the sun can give. And what about if you're supplementing CO2, can't they use even more light than what the sun can provide?

    I don't know but it's my gut feeling that a single 400W light at 2 feet isn't the way I'd want to be growing if I were a plant. I think I'd be wishing the light was closer.
     
  2. The Grow Boss is absolutely correct!
     
  3. Having been growing indoors for over a decade, this is what I've learned, 400-600watt hps are ideal for rooms with 8 ft or less ceilings, 1000w 10 ft or higher. It's the ppfd that's important not the lumens. The sun at noon emits 2000 umols, where the growing day average is high 700s. Here are the umols for three hps bulbs, 1000w - 1850, 600w - 1150 and 400w - 725. That's why a 400w will work just fine. Moving to 2019, the LED is nearing the required ppfd for commercial growing, example is fluence Spyder at 1600 ppf, if you notice, commercial growing is going vertical, they can keep the lights lower because of less heat!
    And the old rule with hps is the hand test, hold your hand over the plant, if it's hot, it to close. With some LEDs bleaching occurs if to close. These plant are being grown under Photo Boost light Engines from Pacific Light Concepts, they are about 15in. above, and the temperature increase is about 5° for both lights. Each light is dimmed to 200w and are capable of 425w each.
     

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  4. Ease of growing for large scale and heat. Smaller grows have more time and energy to track each light for heat and growth.
     

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