Question RE: lights...CFL & HPS

Discussion in 'First Time Marijuana Growers' started by HillCountryHigh, Jan 19, 2010.

  1. I have been doing quite a bit of reading on lights.

    It is my understanding that the 400watt HPS light I have isn't nearly as useful during the vegetative stage as in the flowering stage. My understanding is that the HPS is lacking in the blue spectrum.

    I have recently purchased a couple of cheap clamp type reflector lights and 100W CFL's for germination. I'm going to have two 100W CFL bulbs in each fixture.

    My question is...

    Should I:

    Germinate under the CFLs and then change to the HPS for the vegetative and flowering stages.


    Would it be beneficial to germinate under the CFLs, then use both the CFLs and the HPS for vegetative, and then use only the HPS for flowering?
  2. Is that an actual 100W bulb or is it a 26W bulb? There is a difference between actual watts and equivalent watts.

    I would go with option 2 given the two options.

    Good luck.

  3. My newbie status shows through....:hide:

    26w DAYLIGHT CFL equivalent to 100w. Shows 6500 kelvin.

    Sorry for the confusion.
  4. As long as you know the distinction. But some folks are confused over the whole actual vs. equivalent watts with CFLs. For growers the short answer is: only look at actual watts, totally ignore equivalent watts.

    As for what to use when, remember that, with some reasonable limits, more light is always better than less light, and mixed spectrum is better than either blue-spectrum alone during veg or red-spectrum alone during flower.

    So definitely use the HPS during veg, it's putting out tons more lumens than those CFLs do. To save a little on the energy bill you can start the seedlings with just the CFLs, but the plants will soon outgrow the footprints of those lights.

    CFLs have poor light intensity and so work well only within a couple of inches, parts of the plant further than that don't get much light benefit. So for CFLs either you have to really cover the plants or you have to consider them supplemental lighting to something like HPS.

    Another option you have is purchasing a 400w MH conversion bulb for vegging. I assume you have a magnetic ballast that is not switchable, in which case you will need specifically a "conversion" bulb to run a MH bulb off a HPS ballast. But if the ballast is switchable or digital then you can put a regular 400w MH bulb in it. The MH would be better than either the HPS or the CFLs for vegging.
  5. Though Toasty definetely has way more experience then me.... I would advise you NOT to use HPS during veg. Unless you are planning to veg for a long time. If so, bring it in after 5 weeks or so.

    U should use MH for veg. AND CFL 6500K is very close to this.

    TOASTY is right... if using CFLs... use them within 4-6 inches of the plant.

    If u do use HPS during veg, you can expect your plants to grow tall and stringy without many brachs. CFLS will slow the hieght, but add more banches that will turn into more colas once flowering is brought=more weight.

    When budding, DEFINETELY use HPS when budding though.... if still using CFLs, switch em to 2700K.

    Blue spectrum = VEG = 6500K CFLS or MH
    Red spectrum = BUD = 2700K CFLS or HPS
  6. AS I read his post again... I realize TOASTY.... +rep

  7. Thanks, bro.

    Found a metal halide conversion light on ebay. I hope and think it should work with my 400W HPS fixture.

    And it looks like a steal at $22.95 shipped. Most I've seen run $45.00+ shipped.

    M400NHT/HBU HPS to metal halide conversion lamp - eBay (item 270517434376 end time Feb-17-10 07:27:17 PST)

    Looks like there are a few left if anyone was looking.

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