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How far away do I keep my grow lights?

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    How far away do I keep my grow lights?

    Keeping your grow lights the right distance away improves your yields and reduces the chance of problems! But how far should they be?

    Quick Guide - Read the full tutorial

    Metal Halide & HPS Grow Lights
    • 150W - 10" (25 cm)
    • 250W - 12" (30 cm)
    • 400W - 14" (35 cm)
    • 600W - 16" (40 cm)
    • 1000W - 22" (55 cm)
    LED Grow Lights - these often need to be kept further than growers realize, because even though they don't get hot, they're so bright they can cause light burn!
    • 1W Bulbs - at least 12" (30cm)
    • 3W or 5W Bulbs - at least 18" (45cm)
    • High Wattage (300W+) - up to 30" (76cm) or more
    Fluorescents like CFLs & T5 Grow Lights
    • Keep within a few inches as long as they're not too hot
    • Check by placing your hand where the plant is for 30 seconds, if it's too hot for you it's too hot for your plant
    • Otherwise keep fluorescent lights as close as possible for the best results!
    Each type of grow light (CFLs, LEDs, HPS, etc) has a "sweet spot" as far as how far to keep from your plants. Learn what the sweet spot is for your light!

    #2
    I tried keeping my 600W HPS much closer than 16" and paid the price! Also, no joke on those LED distances! The instructions that came with my P900 says to never have it closer than 18", and no closer than 40" when it's young.

    Comment


      #3
      I need some help on this one. I have 2 auto and 1 photo grow so just learning. I use 400w t5 for most of veg and then 600w hps for flower. I have been trying to keep the room cool enough with fans to leave the glass out of my hood and I use a mover. Considering light to be my number one limiting factor I have been thinking closer(without burning)
      is better.
      Last edited by Flockshot; 09-16-2016, 07:15 PM. Reason: Added (without burning)
      2 auto grows in M3 Organic just add water mix
      1 photo grow in Promix with General Organics go Box
      1 photo White Widow 600w, coco, GH-Best grow yet
      http://forum.growweedeasy.com/forum/...-after-harvest

      Comment


        #4
        Originally posted by Flockshot View Post
        I need some help on this one. I have 2 auto and 1 photo grow so just learning. I use 400w t5 for most of veg and then 600w hps for flower. I have been trying to keep the room cool enough with fans to leave the glass out of my hood and I use a mover. Considering light to be my number one limiting factor I have been thinking closer(without burning)
        is better.
        At some point your plant literally can't use any more light. Although plants are more susceptible when it's hot, light burn can bleach leaves/buds even when it's cool. It's kind of like how snowboarders get sunburn even in winter. You see light burn most often with high power LEDs and air-cooled HPS kept too close.

        Example of light burn under an LED grow light that was too close (even though it was 70°F at the canopy). It can seem like an unexplainable deficiency if you don't know what's causing it!
        led-light-burn-too-close.jpg


        Since you have a light mover your plants are a lot less likely to get light burn, and you can keep your lights closer than normal. Just as a point of reference we tried moving our 600W HPS closer and closer over a few grows and started seeing significant light burn (bleached tips on buds, leaves under the lights turning yellow early, etc) when our 600W HPS was about 12" away, with a new bulb but through glass. Now we keep our 600W HPS about 16" away, which gets bulky buds that stay pristine until harvest.

        Light can be your limiting factor, but it might not be. With a 600W you could expect 10-21 ounces per harvest, and probably a little more with a light mover if you have plants under the whole thing. If you're getting less than that on average there's likely something else in the grow that is limiting your yields (plants too small, lack of training, not enough colas, buds are unexposed, etc). But if you're already getting those yields it could mean you're on the right track by trying to get more light to your plants!

        Comment


          #5
          You had me at bulky and pristine buds. Thank you very much.
          2 auto grows in M3 Organic just add water mix
          1 photo grow in Promix with General Organics go Box
          1 photo White Widow 600w, coco, GH-Best grow yet
          http://forum.growweedeasy.com/forum/...-after-harvest

          Comment


            #6
            After watching Nebula's vid regarding using a Lux meter, I purchased one but am confused about the distance in this regard. I have a 1000 w HPS and at around 22" away, it's only reading about 200 x100 lux...based on the info shared, this isn't anywhere close to what it should be in flower. Also, just decided to try a DE 1000W HPS based on rave reviews and it's even worse! It's so hot that the light needs to be about 3 feet away from the top of the plant but at that distance it's only around 110 x 100 lux. I don't get it. If 65,000 Lux is ideal, then i'm not coming even close to that. Any suggestions?

            Comment


              #7
              Is it possible that with your model of lux meter it's actually being multiplied by 1000 as opposed to being multiplied by 100? So for example 200 x 1000 lux would be 200,000 lux which would make sense for a 1000W that's 22" away. Could you post a picture of the front of the lux meter when it's on?

              Comment


                #8
                It was only 15$ but it says x100 on it....(not sure what that 200000 below means though?).
                the 136 reading is about 5 ft away from the DE and the 301 reading is 20" from 1000w brand new sunmaster bulb.
                Attached Files
                Last edited by francis pharmer; 10-23-2016, 10:59 PM.

                Comment


                  #9
                  I looked up that model of lux meter and I saw that it goes from 0-200,000 lux at the highest setting, so I'm pretty sure that's what the 200,000 on the screen stands for. In the picture you posted it's saying it's getting 30,100 lux. That does seem very low for being 20" away from a 1000W with a brand new bulb, it should be closer to twice that at that distance!

                  I'm not sure if it's possible with your hood, but can you remove the glass so you can measure the light from the raw bulb? If so does it make a huge difference if you measure the amount of lux without the glass in between? I'm not familiar with that lux meter, so it's possible it's just not good at measuring the light from an HPS or is working poorly for some reason. I know that the cheaper lux meters take fewer "points of measurement" and aren't as accurate in unusual light spectrums since they're calibrated to measure the standard light bulb.

                  In any case, I feel almost certain that your 1000W is definitely putting out more lumens than that!

                  Comment


                    #10
                    AHhh, ok- guess I shouldn't have bought the cheapest meter possible. the directions in the book didn't make much sense to me regarding the readings so i think I'll return that one and try the one that you have and then will post what I discover. Thanks immensely for your time and help! It's Greatly appreciated and I've learned a lot from the info you so selflessly post

                    Comment


                      #11
                      Originally posted by SiriusFourside View Post
                      I tried keeping my 600W HPS much closer than 16" and paid the price! Also, no joke on those LED distances! The instructions that came with my P900 says to never have it closer than 18", and no closer than 40" when it's young.
                      That's for sure about the LED distances!! I also paid the price! Why they put such long hanger wires on them is beyond me! We are growing indoors! We have height restrictions!
                      Team AutoMechanics

                      Comment


                        #12
                        for 650 watt cfl self ballast the "sweet spot" is 8 inches (top of plant to light) with the range from 2 -12 inches depending on wattage (100 watt is 2 inches) one must consider the light "foot-print" with the cfl's

                        Comment


                        • NebulaHaze
                          NebulaHaze commented
                          Editing a comment
                          What do you mean by a 650W CFL? Do you have a link to the light fixture?

                        #13
                        Yes - can I give were to get them and not being - spam?" Just want t to help folks in their cultivation

                        Comment


                          #14
                          Yes, we'd love to see what you're using! I personally feel like if you're not selling anything or making money it can't be advertising

                          Comment


                            #15
                            In flowering I keep my 300 watt led light 18" to 24" above the canopy of leaves. On veg I keep my T5 light no more than 4" away. It works fine. Last year Ii kept a 125 watt led light about 12" from the canopy and paid the price with light burn!

                            Comment


                            • ZigZag
                              ZigZag commented
                              Editing a comment
                              Doc_ sounds about the same for me. I have two "350 watt" LED lights and have use them from the start. For the first week I keep them about 36" from the seedlings and then lower them about 2" every week until they are about 20" and then leave them there until 2 weeks from harvest when I lower them to 18" (but I need to watch for burn every day just to be sure...so far no burn at that distance within that time frame). I have yet to try lamps for the veg period, just LED's in the veg mode_Not enough space to change out two types of lights for me but adjusting the distance it seems to work fine...but then I haven't any experience using lamps for the veg period...maybe that would result in more growth during that phase...

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