Light Penetration?

[ChenBenTz]

I have a rectangular grow space (1.6x1M).

So, I thought it best to get two 400w HPS lights.

However, I've been told that one 600w HPS light would have more penetration.

Is this important or should I get the 400w?

Thanks.

 

[BullDogDad]

How tall are you going to grow your plants? And what style? Tall, bushy plants will have a denser canopy. Tall, columnar plants, as in SOG style let a little more light through. But I recall hearing that after a distance of 3ft you lose 70% of your light as a general rule. How will you cool the grow area? A SCROG style grow would be nice in a small area like that. Then penetration is a none issue.

 

[Chunkypigs]

I vote for 2 600's.

 

[Granger2]

Yes, 2 - 600's with adjustable wattage. You can run 2-400's 2-600's, 1 of each. Gives you more options. Good luck. -granger

 

[Smelly_Cheese]

1000k and growem a little taller with less plant count

 

[EclipseFour20]

Get an adjustable ballast that does both, they are not much more in price.

 

[ChenBenTz]

I vote for 2 600's.

No, it's between (1) 600w or (2) 400w.

Two 600w will kill my plants in such a small area.

Get an adjustable ballast that does both, they are not much more in price.

From what I've heard and read, you can't use a 400w on a 600w ballast.

But either way, it doesn't answer my question - does a single 600w have more light penetration than two 400w (effectively 800w)?

 

[Ranger]

No, it's between (1) 600w or (2) 400w.

Two 600w will kill my plants in such a small area.



From what I've heard and read, you can't use a 400w on a 600w ballast.

But either way, it doesn't answer my question - does a single 600w have more light penetration than two 400w (effectively 800w)?

penetration will be fairly close on both 400 and 600 watt HID bulbs so i wouldn't sweat the details on that part of the equation.

there are ballasts that you can run 400-600 and 1k bulbs from depending on your needs and it sounds like that would be ideal for your issue.

for the space you have i would go with an adjustable electronic ballast and get one 600 watt bulb for it. later on if you choose to use it for something else, you have the option of just switching bulbs. lumatek and solis tek make nice e-ballasts. just make sure you get bulbs that run on e-ballasts or pulse start bulbs is what they're called.

 

[dank.frank]

You are looking at basically a 3 x 6 area, there abouts...

Two 400 would light that area better - but I agree - two 600's are a better choice.

2 x 2 = 400w
3 x 3 = 600w
4 x 4 = 1000w
5 x 5 = Gavita 1000w

That's how I view it personally...

You aren't going on overkill with 2 x 600 - you'd just need to either run air cooled hoods or you need to put in about 12btu of A/C to keep thing cooled properly...

But light penetration on a 400w is about 15" tops on canopy, where a 600w will get you about 24" of penetration...keeping in mind, I'm not talking where you will still have fluffy flowers at the bottom, I'm talking for solid, dense, full colas...

I still think 2 x 600w with proper cooling - or if you insist, 2 x 400w. Either way, two lamps are going to give you a more even spread and a better, more evenly consistent canopy. Otherwise you end up with a "U" shaped canopy, where the plants on the outside edge get taller and lean inwards reaching for the area with peak light. The plants in the center will remain a bit shorter and tighter internode distances as a result of being under direct light, and the plants leaning inward on the sides can start to block some of that light as they begin to lean over the top of them...

Just my take on it.



dank.Frank

 

[ChenBenTz]

You are looking at basically a 3 x 6 area, there abouts...

Two 400 would light that area better - but I agree - two 600's are a better choice.

2 x 2 = 400w
3 x 3 = 600w
4 x 4 = 1000w
5 x 5 = Gavita 1000w

That's how I view it personally...

You aren't going on overkill with 2 x 600 - you'd just need to either run air cooled hoods or you need to put in about 12btu of A/C to keep thing cooled properly...

But light penetration on a 400w is about 15" tops on canopy, where a 600w will get you about 24" of penetration...keeping in mind, I'm not talking where you will still have fluffy flowers at the bottom, I'm talking for solid, dense, full colas...

I still think 2 x 600w with proper cooling - or if you insist, 2 x 400w. Either way, two lamps are going to give you a more even spread and a better, more evenly consistent canopy. Otherwise you end up with a "U" shaped canopy, where the plants on the outside edge get taller and lean inwards reaching for the area with peak light. The plants in the center will remain a bit shorter and tighter internode distances as a result of being under direct light, and the plants leaning inward on the sides can start to block some of that light as they begin to lean over the top of them...

Just my take on it.



dank.Frank

According to this graph:

http://www.thctalk.com/gallery/data/500/HPS-Light-Distance-Chart.jpg

A 400w will reach 21" and a 600w will reach 29".

But my question is - is that still valid for TWO 400w? Wouldn't that equal 800w and thus be 40"?

Also, 1200w for 18 square feet is 70w per square foot.

I was told that the max should be 70w, so that's kind of a lot..

 

[EclipseFour20]

...From what I've heard and read, you can't use a 400w on a 600w ballast.

But either way, it doesn't answer my question - does a single 600w have more light penetration than two 400w (effectively 800w)?

I have 400 watt MH/HPS ballasts that is adjustable to 250 watts...plus "turbo" (400w bulb).
I have 600 watt MH/HPS ballast that is adjustable to 250 & 400 watts (600w bulb)
I have 1000 watt MH/HPS ballast that is adjustable to 400 & 600 watts....plus "turbo" (1000w bulb)

With the 1000 watt ballast, it can use a 400 watt bulb provided the ballast switch is set to 400w only. It can also take a 600 watt bulb provided the switch is not on the 1000w setting. A 400 watt bulb at the 1000w setting is "kaboom".

Are two lamps better than one? Yes, if you want to reduce/eliminate shadowing. No if you want to keep your initial cost at a minimum (1 setup instead of 2) and your monthly cost squeaky tight (1200 watts of usage instead of 1000 watts).

I use 2-600 watt lights instead of a single 1000 lamp and have very little shadowing and excellent light penetration. My lamps can be closer to the buds with 600 watts and I have very little height limitation. With 1000 watts, you need space above the lamp (6" minimum), the light height (6-10") and the distance between bulb and plant canopy (12-18") for 1000 watts...about half that if 600 watts. How tall do you grow? If you grow trees....then 1000w plus is your answer. If you grow bushes then less than 1000w is your answer.

 

[dank.frank]

I've run at 100w per square foot without an issue. The plants will make use of the light as long as they have the proper nutritional input to make use of the higher metabolic rates provided by high intensity lighting...

One of my favorite small set ups is a 400w in a 2 x 2 - simply because it allows the smaller wattage to produce nug density comparable to a 1k...which honestly, once you grow with a 1k - it's hard to be satisfied with anything less.

The heights I stated aren't for adequate growth - but for TRUE colas - not lower fluffy trim nugs.

No...2 x 400w doesn't change the penetration of the bulbs in anyway....it just changes the spread and distribution of that light.



dank.Frank

 

[MostlyMe]

I've never understood the concept of light penetration, at least the way growers talk about it. If you consider the light source as a single point, the energy it emits has to divide itself over the surfaces of ever getting bigger spheres as it radiates out, which scales with r². So yeah: the intensity drops off rather quickly, but why would it depend on the source? Yes, at the same distance the 'penetration' of a 400 watt is less than that of a 600 watt, but only because the light power it emits is lower to begin with.

 

[EclipseFour20]

Watts, lumens...are good things to know, but as cultivators we should be focusing on PAR, Photosynthetic Active Radiation. "It is a measure of the visible light spectrum with relationship to plant growth. It does not take into account the UV or IR ends of wave spectrum, just visible light."

This site contains a detailed comparison of PAR & lumen levels using various ballasts with different 1000 watt bulbs; summary info for 600, 400 & 250 watt lamps only. Not all lamps or ballasts are "equal". http://www.hhydro.com/plant_grow_lights_par_testing.html

Lumatek ballast seems to be the winner with the greatest PAR output; bulbs are all over the place.

This interesting graph shows PAR% at different distances for bulbs between 150-1000 watts.

For 100% PAR, distance from bulb varies-
1000w 21"
600w 17"
400w 13"

Forget about "watts per foot" or "lumens", they are nice but PAR is where the big boys play.

 

[ChenBenTz]

Guys, I get that the penetration of a single 600w bulb is greater than the penetration of a single 400w bulb.

What I'm asking is - if you put two 400w bulbs won't their penetration be greater than a single 600w?

 

[ChenBenTz]

I've never understood the concept of light penetration, at least the way growers talk about it. If you consider the light source as a single point, the energy it emits has to divide itself over the surfaces of ever getting bigger spheres as it radiates out, which scales with r². So yeah: the intensity drops off rather quickly, but why would it depend on the source? Yes, at the same distance the 'penetration' of a 400 watt is less than that of a 600 watt, but only because the light power it emits is lower to begin with.

Yes, exactly!

Total wattage should equal penetration.

I don't understand why everyone thinks that 600w will penetrate better than 800w..

 

[dank.frank]

But how does any of that tell him how much light he needs to light a given square footage... ???

All that shows is distance of the light from the top of the canopy...which is great / useful information - but doesn't address the question being asked.

-----

Because it's NOT 800w...it's 2 x 400w. That doesn't magically increase the penetration ability of a bulb. You aren't increasing the wattage - you're increasing watts per sq ft - that's different...intensity of the light available doesn't make the power of that 400w bulb greater...it just creates a more even distribution of that light.



dank.Frank

 

[Ranger]

Yes, exactly!

Total wattage should equal penetration.

I don't understand why everyone thinks that 600w will penetrate better than 800w..

you can increase lumens and PAR watts by adding two bulbs together, but not intensity. if you're having trouble understanding that, then no one here can help you as that's the first hurdle you must overcome.

 

[Granger2]

2 - 400s are spread out. If you had a fixture with 2 400s in it, side by side, then you would get more penetration. Or if you had an 800w bulb, you'd have more intensity/penetration over a smaller area. The 800 watts is spread out, giving you no more intensity. -granger

 

[EclipseFour20]

But how does any of that tell him how much light he needs to light a given square footage... ???

All that shows is distance of the light from the top of the canopy...which is great / useful information - but doesn't address the question being asked.

-----

Because it's NOT 800w...it's 2 x 400w. That doesn't magically increase the penetration ability of a bulb. You aren't increasing the wattage - you're increasing watts per sq ft - that's different...intensity of the light available doesn't make the power of that 400w bulb greater...it just creates a more even distribution of that light.



dank.Frank

Well gents, that's easy. Reverse math is required--calculate the number of watts required to equate to at least 50 watts per square foot.

Square feet and equivalent size for 50 watts/foot equivalent--
250w 5' (2.24' x 2.24')
400w 8' (2.83' x 2.83')
600w 12' (3.46' x 3.46')
1000w 20' (4.47' x 4.47')

If you replace the 1000w lamp with a pair of 600w lamps in the same 20sq/ft space...you will have 60 watts per square foot instead of 50 watts. BTW, not saying 50 watts is the goal, rather 50 watts is the bare minimum for average yields.