Lumen, Lux, and plant response

ok so ive been learning alot more about lighting lately wrather than maryjane herself and it seems to be that lumens dont add up but if a certain energy source can produce 10,000 lumens and a identical source next to it will produce 10,000 lumens it will still remain 10,000 lumens but the LUX add up... i still dont know that much so do plants respond to LUMENS or LUX because i know strecthing occurs if u dont have enough light but light can be both lumen and lux and i really have no room for my next grow to be strecthing and im planning on using 42 watt cfl's that produce 2700 lumens and the average good lighting for as maryjane plant is 5000-10,000 lumens per square foot than i am fuked and as for the LUX PSF i dont know and i would really like some help on this

I don't wanna get too in deep (and probably over my head) But a general summation might be:

Coverage. Tall plants will need more light down low. Fat plants need more all over, etc. Its a ballancing act of bulb intensity and the number of bulbs, HID, CFLs, T5s etc. Along with locations of bulbs. You want light on every leaf, in a perfect world.

A single big HPS on top, might not be as good as a smaller HPS on top and a few CFLs in the corners/lower. But this depends on room, grow style, plant style&strain, etc. Another grower might do better with a single humongicoid HPS above the plants.

SoG, LST, ScrOG, clone, seedlings, strains, etc all factor in.

A little thought ahead of time (hopefully modest upfront, but with designed-in room for growth) can help a ton.

but what do plants respond more to lumens or lux??

anybody???

Take a look the thread in my signature. The reason you have probably not gotten too many responses is that you are asking for a rehash of light theory that would take pages to do properly. You can find many threads dedicated to this topic.

Lumens and lux both add. Lumens are raw light that is emitted by the bulb. Two bulbs at 5000 lumens makes 10000 lumens, but says nothing about the amount of light striking the plants.

Lux is the measure of lumens per unit area, and is the measure of lighting intensity relevant for plants. It decreases with distance from the bulb as roughing 1/d^2.

You ever smoke that koolaid?

I thought lumens didn't add---I thought you were only spreading the light out with more bulbs--I thought Al. B FUCT had a post where he showed one bulb with a light meter and 2 bulbs with the light meter and the lumens didn't increase??--I also know I have a 8 bulb T5 and the lumen output is calculated by adding all 8 on the rating. Would like to know??? thanks

n00b_marijuana_grower said:

but what do plants respond more to lumens or lux??

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Unfortunately, they're both the same thing - sort of! That is to say that they are both standard units of measure used in the Lighting Industry. The really sad part (for us growers) is that the lighting industry bases its' measurements on what people actually see with thier own eyes. The appearant brightness is what is really being measured, in other words, the light that "appears to be brighter" to us (people) gets a "higher" measurement (more lumens). The problem with this system is that human vision is more sensitive to the color Green (probably has something to do with the fact that we all used to live in the bush - anyway, I digress!). The result of this sensitivity is that the "Green" spectrum of light measures really high in lumens. What really sucks is that plants have very little use for Green light.

So there you have it, both lumens and lux are rated "artificially" high if they contain Green light (which is basically useless to plants). On the other hand, the Red and Blue spectras of light register as being less powerful, i.e. less lumens, even though Red and Blue are the spectras that are primarily used by plants. Are you confused yet?

The bottom line is - the plant doesn't give a Rat's Ass what Green light does for us, it mostly cares about Red and Blue. If you understand this, you can see that lumens (or lux) aren't really a very good meaurement to use for grow lights -they're just the only (common) measurements that the lighting industry makes available.

Lumens or lux can only be used accurately (for growing) when comparing bulbs of the same type against each other because the same type of bulb usually has a similar spectrum (Metal Halide vs. Metal Halide, Daylight CFL's vs Daylight CFL's, etc.). Otherwise, knowing the lumens of a certain bulb is pretty useless unless you also know the spectral distribution of that bulb.

I think I'll stop now - I'm getting a headache!!!

It's less about lumanage, more about PAR and KELVIN.

DR. VonDankenstine said:

I thought lumens didn't add---I thought you were only spreading the light out with more bulbs--I thought Al. B FUCT had a post where he showed one bulb with a light meter and 2 bulbs with the light meter and the lumens didn't increase??--I also know I have a 8 bulb T5 and the lumen output is calculated by adding all 8 on the rating. Would like to know??? thanks

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The way I understand it is - lumens don't add, because two sources of light @ "x lumens" aren't any more intense than one source @ "x lumens". There is just "more light energy", so it will cover a bigger area - it wont appear "Brighter".

It is similar to two cars, hooked together, doing 50 MPH - it doesn't add up to one car doing 100 MPH. Radar will "see" it as one "Big" car doing 50MPH. "Speed" and "Brightness" aren't the same thing - but I think you can see the similarity.

T.H.Cammo said:

The way I understand it is - lumens don't add, because two sources of light @ "x lumens" aren't any more intense than one source @ "x lumens". There is just "more light energy", so it will cover a bigger area - it wont appear "Brighter".

It is similar to two cars, hooked together, doing 50 MPH - it doesn't add up to one car doing 100 MPH. Radar will "see" it as one "Big" car doing 50MPH. "Speed" and "Brightness" aren't the same thing - but I think you can see the similarity.

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No, this is a poor analogy. A better analogy would be to ask if a barrier in the way of the two cars would care whether there was one or two.

Take my word for this guys, I study and apply this theory for a living.

Click the stickied thread in my signature called "lumens, lux, and adding it all up" for an explanation of all the theory you could want and an experiment proving it. The only thing going on in this thread at the moment is conjecture.

P.S. There is also discussion in the aforementioned thread about PAR and lumens. It's true that lumens are a poor measure of useful light for a plant, but it is indicative of the raw power of the bulb. And yes, green light IS useful to a plant.

well if ur first link it says that lumens DONT add up and in the 2nd it says that lumens DO add up but for some reason im trustin u and it relieved all my worries thnx cee

Shredder111 said:

It's less about lumanage, more about PAR and KELVIN.

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yep im with u on this 1, ive been reading that its par that is important,that is some of the light produced by certain bulbs is invisible to the plant so is wasted.

n00b_marijuana_grower said:

well if ur first link it says that lumens DONT add up and in the 2nd it says that lumens DO add up but for some reason im trustin u and it relieved all my worries thnx cee

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Where does it say they don't?

del66666 said:

yep im with u on this 1, ive been reading that its par that is important,that is some of the light produced by certain bulbs is invisible to the plant so is wasted.

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Which light are you referring to?

nvm i the first time i guess i really didnt get it wit all that smart talk juss read it over and now i get it ight makes more sense to me