Does the amount of watts even matter? From what I understand lumens are important?

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SolRosenberg

Active Member
I am trying to purchase a light for my first grow and I am trying to determine what is best. Ive seen people say that 50w per sqft is recommended. Why is this, what does electricity usage have to do with the light output per square foot?

Ive also seen someone say 10k lumens per sq foot which makes more sense.

I am just trying to figure out what is best before I make my purchase.
 
2

2ndGen

Member
Yeah, you want to measure lumens, since wattage varies wildly depending on the type of bulb. Aim for 7-10,000 lumens per square foot. This thead has a lot of good info about how much light you need and how much you get out of different types of bulbs.
 
axjnkee

axjnkee

Well-Known Member
Here we go again. Lumens are a measurment of light seen by the HUMAN eye. Plants do not see lumens. The light meters used to measure lumens pick up the green yellow spectrums as they are the brightest. Plants do not see this spectrum and it is useless for growing.
 
ChroniComedian

ChroniComedian

Well-Known Member
Axjnkee is right, all you have to do is check a dictionary to know that lumens are a measurement of the human perception of light. You need to pay attention to the wattage, if you are wanting a good light and only care about having something powerful then a 400-600W HPS is probably what you want. Metal Hallide's are generally better for vegging plants, HPS are better generic all around lights. I'm personally sporting a 400w HPS and a 70W LED UFO which puts out an equivalent amount of light to a 400W HPS because it doesn't waste energy in unneeded spectrums such as yellow and green, and doesn't waste light in reflectivity, (plus it adds absolutely no heat to my room).
 
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SolRosenberg

Active Member
ChroniComedian said:
Axjnkee is right, all you have to do is check a dictionary to know that lumens are a measurement of the human perception of light. You need to pay attention to the wattage, if you are wanting a good light and only care about having something powerful then a 400-600W HPS is probably what you want. Metal Hallide's are generally better for vegging plants, HPS are better generic all around lights. I'm personally sporting a 400w HPS and a 70W LED UFO which puts out an equivalent amount of light to a 400W HPS because it doesn't waste energy in unneeded spectrums such as yellow and green, and doesn't waste light in reflectivity, (plus it adds absolutely no heat to my room).
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i was going to get the switchable one its like 160 for a 400w with everything and comes with 2 bulbs
 
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growone

Well-Known Member
i was going to get the switchable one its like 160 for a 400w with everything and comes with 2 bulbs
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that will certainly work, might be a bit pricey
don't overlook cfl's for vegging, they can do a very nice job for low $
they also make good side lighting in a HPS grow
 
phyzix

phyzix

Well-Known Member
ChroniComedian said:
70W LED UFO which puts out an equivalent amount of light to a 400W HPS because it doesn't waste energy in unneeded spectrums such as yellow and green, and doesn't waste light in reflectivity, (plus it adds absolutely no heat to my room).
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If you found a light (resistor) that doesn't put out heat you should probably patent it. Nobel is probably in order.
 
bobbyhopefeild

bobbyhopefeild

Active Member
ChroniComedian said:
Axjnkee is right, all you have to do is check a dictionary to know that lumens are a measurement of the human perception of light. You need to pay attention to the wattage, if you are wanting a good light and only care about having something powerful then a 400-600W HPS is probably what you want. Metal Hallide's are generally better for vegging plants, HPS are better generic all around lights. I'm personally sporting a 400w HPS and a 70W LED UFO which puts out an equivalent amount of light to a 400W HPS because it doesn't waste energy in unneeded spectrums such as yellow and green, and doesn't waste light in reflectivity, (plus it adds absolutely no heat to my room).
Click to expand...

you guys hav completely missed perhaps the most important measure of light for plants ; photosynthetic active radiation or PAR, only some of the spectrum of light is used by plants, during veg plants need blue light for leafy growth, so that 400w hps is only actually giving plants a small portion of the energy pumped into the light as the red spectrum light can't be utilised , thats why metal halide is better for veg as it contains alot more PAR than hps.
 
2

2ndGen

Member
axjnkee said:
Here we go again. Lumens are a measurment of light seen by the HUMAN eye. Plants do not see lumens. The light meters used to measure lumens pick up the green yellow spectrums as they are the brightest. Plants do not see this spectrum and it is useless for growing.
Click to expand...
Then how do you figure out how what wattage of light to use, or how many lights to use?
 
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growone

Well-Known Member
Then how do you figure out how what wattage of light to use, or how many lights to use?
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this is why 50 watts per square foot is often quoted, it normally gives very good results
the PAR measure is what the plant 'sees' and is the 'right' way to be very exact on light spectrum
but the simple HPS formula of 50 watts/sq foot will work just fine
 
axjnkee

axjnkee

Well-Known Member
phyzix said:
If you found a light (resistor) that doesn't put out heat you should probably patent it. Nobel is probably in order.
Click to expand...
I run LED's as well (236w to be specific) and they emit VERY VERY LITTLE heat. They run 12-18 hrs a day depending on cycle and are always cool to the touch, or luke warm at the worst. My grow area (4x4 closet) stays a very comfortable 76 degrees all day.
 
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