How Much?

Discussion in 'Growing Marijuana Indoors' started by Pothead Pete, Jul 15, 2003.

  1. How much light is too much? I have heard a point of diminished returns occurs around 50 watts per square foot. Is this true? My flowering chamber is 3x5 x6 1/2 feet. I am currently using a 400MH for a total af 26.6 watts per square foot.My question is , I was thinking of adding a 400watt HPS. Can my plants take 54 watts per square foot as long as I keep the temp under control. If I could add the HPS then I would be flowering using both the blue and red light spectrums. I just am not sure if this will overwhelm them. I don't want to hurt my girls, just do the best I can in this limited space. Any help would be appreciated. PEACE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
  2. IF you can control the heat, it should be no problem, its just that 2 400w HPS would get quite hot, but if you can control the temp, go for it.
  3. the most you could move them away from the light just alittle bit to help keep the heat off the canopy good luck
  4. 54w/sq' is fine.


    Over 70 and you have to start questioning whether it's worth the effort.

    The diminishing returns factor comes with efficiency, more W = more extra £ (or USD in most of your cases) than extra quantity of harvest hence more £ per Gram.
  5. Nb the above is ONLY talking about light.

    I agree cooling it may be a problem.

    Have you thought about a 600 on a light mover moving along the 5ft length?

    600/15 = 40w/per square foot. Add the light mover and coverage is pretty efficient.

    Frees up a four hundred for a second smaller grow space too.
  6. I'm not a rich man. I already have a 400MH. I have an awesome veggie chamber, which uses 8 40 watt tubes. I veg my plants to 25 inches and in the flowering chamber they go.The heat isn't a problem right now as I am only using one 400MH.I also live in a cool basement apartment, with the temp around 70 farenheit.If I add a 400HPS will it get too hot? How can I combat this? I also have an oscillating fan in both chambers.
  7. The extra 400w will add a significant amount of heat (you run one now so you know how hot it can get).

    The only way to combat it is more airflow.

    Cool the hoods (cooled hoods aren't cheap but there are "ghetto" ways to do it) or ventilate the room more.

    "Not a rich man"

    600 might work out more economical in the end (200w less over x amount of months) even with the slight extra cost of purchase than an EXTRA 400. However you of course will get a larger square foot coverage with 2 x 400 so i guess it's 6 of one half a dozen of the other as we say here.


  8. I think it only sounds logical that since I already have 400 watts of the blue spectrum , that I add 400 watts of the red spectrum,so as to get the best of both worlds. I am seriously going to consider my options due to limited space.

    Attached Files:

  9. id veg with the 400mh and grow them a bit taller then flower under a 400w hps. id take the 8 4ft tubes and mount them in my flowerin room to light the lower parts of the plants and get more bud off each plant that way.

    thats just wot id do tho, dont expect u to do it pete but i thought id throw my 1p worth in incase some1 was reading this that had similer lights and space.

  10. can ya explain some ghetto ways plz m8? :)

  11. If you can though keep the MH on for flowering along with the HPS as it emits small amounts of UV encouraging resin production.

    Using the flouro's would take away from vegging plants.

    See below for some "ghetto" hoods.

    There is no fool proof guide but the general ideas remain the same.

    Get creative mang.

    Hood 1

    Hood 2

    Hood 3

    Hood 4

    Hood 5

    Hood 6

  12. 320 watts gives me 32 watts per square foot of flouros ,I am very pleased with the results. I get 24 inch tall bushes and into the flowering chamber they go. They get to about 44 inches and I bend if I have to. I am marginally satisfied with the 400MH ,which provides 26.6 watts per square foot. I am probably going to go and add the 400HPS within a month or two. That will give me 53.2 watts per square foot. And I get both the blue(MH) and red(HPS) spectrums. I hope it isn't overkill. I just can't use the tubes for side lighting. The veggie chamber is just too valuable!!!PEACE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1
  13. Its more of a effeciency curve because you will yeild more with more wats per foot but less G per watt.

    shureshot i read on OG that a comercial grower grew some of the best bud switching form MH to hps weekly. but would it be teh same to haev both on at the same time?

  14. Yes, it would definately be better to have both on assuming you are staying within a useable watt limit of course and not just pumping wasted lumens at a plant that can no longer use them. The obvious downside is power consumption. I would think for commercial growers efficiency is the key, best quality yield for lowest possible outage so maybe this wouldn't be the way to go in their case.

    Obviously for the personal use we all grow for quality is the way to go.

    You could say maybe instead of a 600w HPS use a 400w HPS and 400w MH but I think the disadvantages of the loss of red spectrum would outweigh the advantages of the addition of UV.

    I'd like to do some experimentation with different voltage UV lights run for different time schedules during flowering using identical clones in a controlled space to prove it for sure but have neither the space, nor the time to do so. What's cannabis? I mean geez.

    What I think would be a good think to do though is stick a UV light on for 5 minutes in every hour of light (on a separate timer obviously) and see if anecdotally the buds look/taste more resin'y. If you do it with a strain you know well you may be able to make some subjective judgement and ultimately that's what this is all about. Getting the best results for YOUR grow.

    I would add though that an easy way to add a little resin production that seems to work (again anecdotally) is a lowered humidity during flowering. This seems to kick the plants into producing more resin perhaps to aid with water retention in the vunerable leaves and buds.

    Nobody is actually 100% sure what the resin on cannabis is actually FOR though the theories are wide and varied and it may indeed serve ALL of these purposes.

    Another one of natures irresistible mysteries.

  15. For 15 square feet would the addition of another 400 watt lamp increase production? Isn't this especially true if I combine both MH and HPS,while keeping down the temp to around 75 farenheit and keep all other variables the same? Any input appreciated !!!! Peace!!!!!
  16. Is 800 watts too much light for a 3x5 ft space? Will it overwhelm my plants?

  17. that shud give u just over 50w per sq ft, spot on id say. just think about how ur gonna hang the lamps to get the best spread of light.
  18. I am going to go with the extra 400HPS. I hope to double harvest weight for my plants. I'll keep this thread alive for a while and report weekly on my progress. Thanks a lot for all your input guys. I am going to go for it!!!! PEACE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
  19. Im predicting %60-75 increase in yeild.

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