Light Penetration?

L

Landing

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I'm curious about something.

Why is it that people claim that a single 600w bulb will have more light penetration than two 400w?

Technically speaking, if the wattage is higher, wouldn't the resulting 800w have more penetration?

I need to decide which to go with because I have a rectangular growing space and need even coverage.
 
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I think it is because the Two 400 Watt bulbs are acting independently of one another. Kinda like having two cars going 40 miles an hour each. That doesn't mean they are hitting a stationary object at 80 miles an hour. I liked a 600 Watt HPS because it had the best lumen to watt ratio. jmo
 

learning2fly

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Hi Landing,

what size is your grow space?

Lumens per square foot are very important and you want to aim for 3,000~5,000 l.p.s.f.....



And like Hamster I too recommemd the 600's!


peace and pot :)
 
L

Landing

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I think it is because the Two 400 Watt bulbs are acting independently of one another. Kinda like having two cars going 40 miles an hour each. That doesn't mean they are hitting a stationary object at 80 miles an hour.
But what if they hit it at the same time? I mean, if there is 800w of light in an enclosed space, wouldn't the penetration be higher than a single 600w bulb?

...

You guys are recommending the 600w because of lumens?

But don't 600w HPS bulbs give off 85,000 lumens and 400w give off 55,000? That's almost the same amount of lumens per watt and it would be 110,000 for the two 400w.

And what about light penetration and coverage? One 600w isn't going to cover my 1.6mx1.1m space very well. The plants on either end aren't going to get as much exposure..
 
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600W hps=90-96,000 lumens
400W hps-50-55,000 lumens

Given the choice I would run two 600w HPS over two 400W HPS. Or in my case I had a 400W HPS and added a 600W to it.
 
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A 400W is only going to penetrate so far--no matter how many of them you have. Don't know if you have ever used any kind of drop lights or halogens in dark spaces, but that really shows how far different wattages of lights travel. For instance, 2 250W halogens will not light the end of a crawl space, but a single 500W will.
 

Hackerman

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I am not 100% on this but I believe the penetration would be measured by radiant and luminous intensity.

Intensity is measured in lumens per steradian and watts per steradian. Picture a 3 dimensional cone starting at the center of the light and projecting out like a cone. That is a steradian.

So, the way I see it, if 2-400w lights are placed close enough together that their cones intersect, the light intensity (penetration in this case) where the 2 cones intersect would be the equivalent of an 800w light. However, everywhere else would only have the intensity of a 400w.

Make sense?
 
L

Landing

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I am not 100% on this but I believe the penetration would be measured by radiant and luminous intensity.

Intensity is measured in lumens per steradian and watts per steradian. Picture a 3 dimensional cone starting at the center of the light and projecting out like a cone. That is a steradian.

So, the way I see it, if 2-400w lights are placed close enough together that their cones intersect, the light intensity (penetration in this case) where the 2 cones intersect would be the equivalent of an 800w light. However, everywhere else would only have the intensity of a 400w.

Make sense?
No.. it doesn't. I'm sorry.

If you have two 400w an inch apart, then you're producing 800w of light because light is directly stackable.

If 600w can penetrate x inches then the 800w should penetrate further.

I don't see why it would have the intensity of 400w.

600W hps=90-96,000 lumens
400W hps-50-55,000 lumens

Given the choice I would run two 600w HPS over two 400W HPS. Or in my case I had a 400W HPS and added a 600W to it.
I'm not sure what you're looking at but the SunMaster Dual Spectrum bulbs I buy are 60,000 for the 400w and 90,000 for the 600w.
 
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I looked at the specs on a couple average 400W and 600W HPS bulbs. The low on the 400W was 50,000. The highest I saw was 55,000. Same with the 600W. Average specs. I didn't know we are talking about expensive HPS bulbs. I never used them because I always have done fine yield wise with the cheapo bulbs. As for your question. We have tried to answer it with our opinions as best we could. I think Hackerman's explanation makes perfect sense. If you don't agree with it than fine. You asked and we tried to answer.
 

zem

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you have 2 guns that shoot 2 projectiles 400 ft each, they will not hit a target at 600ft no matter how many guns you bring where as 1 bigger gun that shoots 600 ft will hit it, simple
 

Hackerman

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Bad example. You're comparing mass and energy to lighting and luminance.

Think more like 2 heaters set 10 feet apart. Certain areas of the room will be hotter. Where? Where the energy from the 2 heaters intersect. I see it the same way with lighting. I could be wrong.
 

MR1

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One flashlight with a 2 watt bulb will illuminate an object at 10 feet lets say and a 5 watt flashlight will illuminate an object 20 feet. Putting two 2 watt flashlights will not illuminate the same object at 20 feet , the intensity of the two 2 watt flashlights will be double if aimed at the same spot but penetration will not be double. Since the lights will be separated you will only have penetration of one light and any overlap will be higher intensity not penetration. Having more than one light gives you more coverage. That is how my stoned self sees it.
 

Hackerman

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One flashlight with a 2 watt bulb will illuminate an object at 10 feet lets say and a 5 watt flashlight will illuminate an object 20 feet. Putting two 2 watt flashlights will not illuminate the same object at 20 feet , the intensity of the two 2 watt flashlights will be double if aimed at the same spot but penetration will not be double. Since the lights will be separated you will only have penetration of one light and any overlap will be higher intensity not penetration. Having more than one light gives you more coverage. That is how my stoned self sees it.
That makes sense. Not sure if it's an accurate statement or not but it makes sense.

As my physics teacher in college used to tell me when I believed something that "made sense"...... He would say, "Prove it". LOL And, he would demand footnotes and valid documentation for my proof. Loved that guy. Great teacher. He never taught me anything.... he always made me learn it for myself.

I have looked around a little and I have not found any info directly relating to what we are discussing. I'll spend a little time today and see if I can find some real facts [with footnotes] LOL.
 

Hackerman

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I politely refuse to stoop to the level, of arguing with stoned peeps :)
That does not do a direct comparison of 2 lights of a specific wattage vs a single light of greater wattage which is what we are discussing. It's nice input regarding one light but invalid for the purpose of this discussion.

Data invalid.... go back and do it over.

LMAO
 

zem

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a bulb can penetrate xft no matter how many bulbs you stuff beside it it only penetrates xft. ask your physics teacher for further explaining LOL
 

Hackerman

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a bulb can penetrate xft no matter how many bulbs you stuff beside it it only penetrates xft. ask your physics teacher for further explaining LOL
If you can't explain it, how do you know it's true?

In the laws of physics, you can not say something is true or false unless you have proof.

Not an argument. Just the way it is on your planet.
 

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