Light Penetration

Does the same PAR output from bulbs of different wattage result in different depths of light penetration?

I've seen a lot of people on various forums post that 1000w HPS bulbs penetrate better than 600w HPS bulbs, and that HIDs penetrate further than T5s in general. I haven't found any other source that backs up any of these claims. I've researched the science of it, and from my understanding there is no reason light emitted from different sources at the same ambient PAR level would penetrate any more or less than each other - 100,000 lumens of spectrum-identical bulbs is 100,000 lumens, doesn't matter the wattage of the bulb used to generate that light, and either 100,000 lumens will penetrate equally. So it seems to me that there is a fairly popular myth being spread among certain growing communities, one that favors big bulbs for no reason.

Yes but bigger bulbs is the only way to get more lumens. If you have researched it as you say then you already know that lumens do not "ADD". If i have a 1000w watt hps with a 150,000 lumen bulb, my plant is receiving light at the intensity of 150,000 lumens per given area. If i had four 250w hps's each with a 33,000 lumen bulb, my plants would not be receiving 132,000 lumens per given area. They would still be receiving 33,000 lumens just over a wider given area. Light intensity is the factor that alters penetration depth. Did this help you understand it better? I hope so cause i'm NOT LOW right now and i hope I didnt't write it wrong lol.

corvetteguy said:

Yes but bigger bulbs is the only way to get more lumens. If you have researched it as you say then you already know that lumens do not "ADD". If i have a 1000w watt hps with a 150,000 lumen bulb, my plant is receiving light at the intensity of 150,000 lumens per given area. If i had four 250w hps's each with a 33,000 lumen bulb, my plants would not be receiving 132,000 lumens per given area. They would still be receiving 33,000 lumens just over a wider given area. Light intensity is the factor that alters penetration depth. Did this help you understand it better? I hope so cause i'm NOT LOW right now and i hope I didnt't write it wrong lol.

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Actually closing the distance of your light source and your canopy produces more lumens. Its a inverse proportion.

he said "penetration" hahahahahahahahahhahahahahahhhhhhhhhhhhhhaaaaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhhaaaaaaaaaaaaaaaa

HAHAHA hard penetration"

Kool & The Gang wrote a song about penetration didnt they??

PEEENEEEETRATE good times cmon...lets penetrate
Theres a party "growin" on right here...its light penetration...that matters listen clear
So take your head highs, and your couchlock tooooo...we gonna penetrate that canopy for you...come on now...

PEEENNNETRRREEEETIOOOON...

OK I'm done...damn thats good weed...

calicat said:

Actually closing the distance of your light source and your canopy produces more lumens. Its a inverse proportion.

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Yes it is but in the real world, if your trying to grow with it light intensity matters yes i can move a 250w hps close enough to equal the lumen output of a 1000w watt at the top of the plant, but it wont equal it four feet down the plant the differance will be greatly affected by the intensity of the light source. Not to mention the closer you have to run your light to the plants the smaller area of plants you can cover. It's an equation of efficentcy based on a real world application.

corvetteguy said:

Yes it is but in the real world, if your trying to grow with it light intensity matters yes i can move a 250w hps close enough to equal the lumen output of a 1000w watt at the top of the plant, but it wont equal it four feet down the plant the differance will be greatly affected by the intensity of the light source. Not to mention the closer you have to run your light to the plants the smaller area of plants you can cover. It's an equation of efficentcy based on a real world application.

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And i'm still NOT LOW lol, look how i spelled efficiency lol.

I use leds and get 7/10 good penetration i made my own panels from christmas lights and its highly effecient but not VERY penetrating. Seriously it works good.

All light* penetrates identically, irrespective of source. For LED arrays it is slightly more complicated because you need to do the calculation for each light source in 3D, but for a single point source light it is simply a matter of dividing the lumens given out at source by the square of the distance from the source. When that value falls below whatever arbitrary value you set as "not enough light for growth" then that is how far it penetrates.

Because of this the "penetration depth" from any point light sources will always be directly proportional to their lumen output. PAR is just a different measure of lumens, so the same applies to PAR.

Edit: *Green actually penetrates more than other light since leaves get in its way less...but I'm talking about light which doesn't get blocked by leaves...

PendulumMan said:

I've seen a lot of people on various forums post that 1000w HPS bulbs penetrate better than 600w HPS bulbs, .

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That is of course.....

ironcross360 said:

HAHAHA hard penetration"

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Huh huh huh huh. He said, "hard."

lol lets penetrate this girl,, HArd doubletime

ironcross360 said:

I use leds and get 7/10 good penetration i made my own panels from christmas lights and its highly effecient but not VERY penetrating. Seriously it works good.

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How about some pics?

Guys, guys, guys, I'm so NOT LOW right now like omg.


What are we, children? The word is high.

Lumens are not par or anything equivalent. Lumens are for humans. Pendulumman was close with his thoughts, but sounded like he thought all hps had the same par. If a light has the same Par meter reading as another, then they will penetrate the same no matter what the wattage or lumens of each source. Par is the true measurement of intensity of usable light by the plant. A lot of the light and lumens that 1000w put out is not used by the plant, just seen by our eyes. That's why LEDs use specialized spectrums, they don't waste energy producing light the plant doesn't want or use. Spectrum/frequency gives the colors of light the plant needs and the par is how much/intense it is putting it out... or penetration!

Mostly only LED companies will show par. Hps just uses/puts out so much, that there is plenty in there to use and grow with it just is not very efficient in concept compared to he new LEDs. LEDs want to show it cause they have the same(very close) usable light without all the extra waste. If a led companies won't show par then probably not worth it and won't get the penetration of hps wattage.
I only know these ...
1000w hps= about 1200-1300 par reading @12"
best led's= about 950 +\- @12"

If this come across as "know it all" or rude I apologize. I have researched a lot and tested certain leds vs hps personally. Spoken with companies about par...some will tell if you call. I have also used a par meter in my own room.

PendulumMan said:

Does the same PAR output from bulbs of different wattage result in different depths of light penetration?

I've seen a lot of people on various forums post that 1000w HPS bulbs penetrate better than 600w HPS bulbs, and that HIDs penetrate further than T5s in general. I haven't found any other source that backs up any of these claims. I've researched the science of it, and from my understanding there is no reason light emitted from different sources at the same ambient PAR level would penetrate any more or less than each other - 100,000 lumens of spectrum-identical bulbs is 100,000 lumens, doesn't matter the wattage of the bulb used to generate that light, and either 100,000 lumens will penetrate equally. So it seems to me that there is a fairly popular myth being spread among certain growing communities, one that favors big bulbs for no reason.

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The point, by the way, about big bulbs is not actually that they are more penetrating (as I already explained, you're right that the source is irrelevant, and only output lumens are needed to calculate "penetration") but that higher wattage bulbs tend to be more efficient for their price, giving out more lumens per dollar and per watt.

Most people will actually agree that 600W is the most efficient HID wattage to go for compared to a 1000W (see Heath Robinson's grow to see what 600W can really do!). So bigger certainly isn't always better!!

tags420 said:

If a light has the same Par meter reading as another, then they will penetrate the same no matter what the wattage or lumens of each source. Par is the true measurement of intensity of usable light by the plant. A lot of the light and lumens that 1000w put out is not used by the plant, just seen by our eyes. That's why LEDs use specialized spectrums, they don't waste energy producing light the plant doesn't want or use. Spectrum/frequency gives the colors of light the plant needs and the par is how much/intense it is putting it out... or penetration!

Mostly only LED companies will show par. Hps just uses/puts out so much, that there is plenty in there to use and grow with it just is not very efficient in concept compared to he new LEDs. LEDs want to show it cause they have the same(very close) usable light without all the extra waste. If a led companies won't show par then probably not worth it and won't get the penetration of hps wattage.
I only know these ...
1000w hps= about 1200-1300 par reading @12"
best led's= about 950 +\- @12"

If this come across as "know it all" or rude I apologize. I have researched a lot and tested certain leds vs hps personally. Spoken with companies about par...some will tell if you call. I have also used a par meter in my own room.

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"Penetration" is simply the distance you have to move your light meter away from the bulb before the reading drops below whatever you consider being "too little light" to grow. PAR simply reflects the spectrum...the light within that PAR spectrum will behave in the same way as light measured using lumens (ie it will obey the inverse square law).

i think what you may have heard was that as far as lumen per watt output, the 600 is more efficient than the 1000. but the 1000 will give you more penetration. distance the light is away from the plant will determine how far into the plant the light will penetrate. this chart is distance for light and not heat. so a non air cooled light will need to be farther away than a cooled light.

Yep. That's the chart I use. In the case of that chart, the penetration is the basically the light yellow section of each column...