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Discussion in 'Indoor Growing' started by kylepc91, Mar 20, 2012.


    kylepc91 Well-Known Member

    1. It was explained to me that more wattage in your light source, either it be LED or HPS, the more penetration your light source has. The comparison was explained to me like this: for every 100 watts of HPS, you need 70-80 watts of LED to equal the same penetration. IE 800watts of LED = 1000watts of HPS.
    Assuming this is correct, and taking the higher number just to be safe:
    HPS to LED conversion (HPS wattage x 0.8 = LED equivalent)
    LED to HPS conversion (LED wattage / 0.8 = HPS equivalent)
    As a reminder, when I say "you need 70-80 watts of LED to equal the same" I mean you need 70-80 watts of actual draw power. So when someone boldly claims they have an 800w LED, ask them how much power it draws. Most of the time LEDs aren't run at full power because if they were, they would burn out relatively quickly. For example I have 2 100x3w LED panels (300 watts) but they only draw 187 watts of power, which means they run at about 62% power, drastically increasing the life on the bulbs, but lowering penetration.

    That being said, is penetration what determines the size of the lower buds? Is that the only thing it determines? If so, using methods like the Scrog method would mean I would need less wattage for penetration?

    2. Some people state that an HID bulb only has 17 usable lumens per watt, while an LED fixture usually has around 43 per watt.

    Does this mean that most of a HID light is wasted?
    Does this mean that the 6000-7500 lumens/ft2 rule isn't that reliable?

    3. With all that being said I arrive to even an even bigger question.

    What is that maximum amount of lumens usable by 1 plant? Is there one?

    4. Assuming that there is a maximum amount of lumens that a plant can use, there has to be a point where wattage only matters for penetration. But also assuming that penetration is only for more light distribution for your lower buds, methods like the scrog method would make it obsolete to have a high wattage bulb, because once you have reached that maximum amount of lumens, the only thing that matters is how well your light is spread.

    Also, are lumens stackable? Say that I have 1 400 watt HPS bulb - 45,000 lumens roughly, then I add another bulb in there for another 45,000, totaling 90,000 lumens. Well that doesn't make much sense to me that they would stack. My logic being this; Bus A traveling at 45 miles per hour stops and lets half of its passengers onto Bus B, which is heading to the same destination at 45 miles per hour. 45mph + 45mph from 2 different vehicles doesn't = 90 mph, as they are both only going 45 mph. Passengers A will arrive to their destination roughly at the same time Passengers B arrive. Except more gas and space on the road was wasted for no different results, when both group of passengers could of taken 1 bus, and been more efficient. The only way this would of been logical is if there was not enough room on Bus A (light spread).Unless you need 2 bulbs just to spread the light out or higher wattage for penetration ( if you aren't using a training method) I don't see the sense in it. Wouldn't it make more sense to just have multiple, lower wattage bulbs for light spread? Seeing as both bulbs are producing the same amount of lumens at the same rate, the availability of light increases but the size and space of the grow area did not, and the rate at which plants photosynthesize did not increase, as they are only going to use what they can use.

    Thank you if anyone read all of this. Hopefully someone can correct me and explain this to me a little better.
    PJ Diaz

    PJ Diaz Well-Known Member

    Busses aren't lights. Lumens are additive if focused on the same point, or you can spread out the lumens over a larger area.

    Gastanker Well-Known Member

    Plants don't see lumen they see PAR. Higher single point light sources "throw" light farther than multiple point light sources. This is to say in simplified terms (we are disregarding bulb wattage efficiency here) that while 2x500w bulbs produces as much PAR as a 1kW light up close they do not deliver that light as far as the single 1kW.

    Let me compare it to a laser. Say you have a 5w laser that goes 1 mile and a 10w laser that goes 2 miles. If you take two 5w lasers and hold them an inch from a card pointed at the same spot it will get really hot. Just as hot as if you were to take the 10w laser and point it at the card from an inch away. But if you took both 5w lasers and pointed them at the same point on a mountain 2 miles away you still wouldn't be able to see the dot.

    This is the reason there is a huge difference between units that use 3w diodes versus units with 1w diodes and those that use even smaller. Both units could be the same wattage (one with more diodes than the other) but the unit with 3w diodes will throw the light much farther.

    polyarcturus Well-Known Member

    someone disproved your point in another thread(light waves bouce off one another) Lumens stack so they might not goes as far, but 2 500w would be more intense than the 1 1000 at optimal distance

    Gastanker Well-Known Member

    Optimal distance being the key word. At equal close distances they wouldn't provide more light, it would be equal, at far distances it would be less light - we're talking hypothetical and not taking into account HIDs wattage efficiency curve (you might have noticed we're talking about 500w bulbs). Keep in mind the hypothetical comparison is to illustrate a light physics point, nothing else.

    If you had enough low light LEDs >1w and were able to get them all close enough to the plants they would work better than high wattage LEDs further away and massed into one area like most pannels - less energy would be lost as the distance the light would travel would be so much less. But spreading out hundreds of tiny LEDs within an inch of all parts of the plant is just absurd. HIDs are a bit different as 600w and 1000w lamps both throw at least several feet.

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