Light Research for Vegetative Growth

[ChatNoir]

1 foot = 30cm
1 cm = 10mm

I have been researching light for some time, and came up with some data. I wanted to share it.

As far as we know, light diminishes directly proportional to the square of distance (d²).

I will be using a lot of calculations in here so get ready, also I must admit that my information is based on calculation and theoretical information.

While researching lights, I came up with a fluorescent tube you will see in attachment. It has just the right spectrum as well as 90~lm/w efficiency. I am assuming all tubes are within proximity of 6cm of plants for our setup. It is a fluorescent tube, 1213.6mm in with 28mm in diameter. 3250lm light power and 6500K in light colour.

We will be using our control as widely used 400W MH lamp with 53,000 lumen output, 123~lm/w effectivity as well as 280mm in lenght. I am assuming, it is housed in a tempered glass cage and hang within 30cm proximity of plant.

Our plants are assumed to be 60cm (2 feet long) and 40cm (4/3 feet) wide. In a 130cm (4 and 1/3 feet) long, 60cm (2 feet) wide cabinet.

We will be using one 400W MH lamp above the plants and in the middle, and 10x3250lm fluorescent lamps around the plants 4 on the top, 3 on the side with 10cm between top lamps and 17cm between each other for the side lamps. We will calculate four different values for both lamps; the lumen value at the bottom of the middle plant, the lumen value on the top of the middle plant, the lumen value on the top of the rear plant, the lumen value on the bottom of the rear plant. Those are point calculations, they do not include rebounding light and for MH lamp, we are ignoring the canopy opacity.

Relative Lumen Values for MH Lamp
Top: 58,0~
Bottom: 6,5~
Rear Top: 21,2~
Rear Bottom: 6,0~

Relative Lumen Values for Fluorescent Lamp
Top: 152,8~
Bottom: 141,7~
Rear Top: 152,8~
Rear Bottom: 141,7~

My conclusion is fluorescent lamps are much more effective in vegetative growth. Please correct me if I am wrong.

 

[ChatNoir]

I forgot to attach lamp data...

 

[The Hemp Goddess]

Wow! Thanks for this. I don't understand all the calculations (or maybe I'm just too stoned), but the relative lumen values certainly seem far better for the fluoros than the MH. As a big fan of T5s, I am not surprised.

 

[massproducer]

I have no idea what all of the calculations mean, but I would have to disagree that Flouros are more efficient then HIDs, wheather for vegging or flowering, with the exception of rooting clones and sprouts.

You have to take into consideration that flouro's are not a new technology for horticulture. This is how things, especially cannabis was grown for numerous years before HID's became common place.

I will agree that flouro's are great for low lighting situations or for micro grows, but it seems that a lot of people are caught up on the heat issues a rising from HID's, but the fact is that watt for watt, HID's create less heat and more light then flouros, so that means 200 watts of flouro's will run much hotter then 200 watts of HID lighting. In my opinion, the problem is not the HID's it is users cooling techniques. IMHO, nothing competes with a well cooled HID

Where did you come up with these numbers for relative lumen Values?

 

[ChatNoir]

I simply, draw the situation, created triangles and calculated the hypotenuse which is the distance of the lamp from canopy. I divided the lumen shed by lamps by d² (hypotenuse²), this gave me the number of relative lumen shed on a point. I also used 3x3 fluorescent set up, instead of 3x4, so numbers came lower than I actually expect for fluorescents.

Con of HID lights, they need to have a GREAT distance, at least one feet, that is why we always have a higher d² so to speak light loses it's power.

Fluorescents on the other than can stand as close as 3cm, their combined heat might be a problem but only one single light will not burn the canopy so they can stay as close as we want, in return have least diminished light shed on the canopy.

That is where I came into conclusion.

 

[massproducer]

Well from what I understand, The Law of Diminishing light doesn't quite work that way, it states that it diminishes to the square of the distace, but this happens after 1 foot. A 400 watt HID should be easily able to be put within 12 inches of the canopy, meaning that the light lossed is very small, you would be getting all most all of your 50,000 lumens.

At 4 feet away a 400 watt HPS would still produce 3,600 lumens, which is more then most Fluoro's emit in total.

 

[ChatNoir]

Well from what I understand, The Law of Diminishing light states that a lamp looses about half of its lumens and light energy every foot. A 400 watt HID should be easily able to be put within 12 inches of the canopy, meaning that the light lossed is very small, you would be getting all most all of your 50,000 lumens.

At 4 feet away a 400 watt HPS would still produce 3,600 lumens, which is more then most Fluoro's emit in total.

12 inches? Don't we need a very good cooling system? And still we are using 9 fluorescent lamps, each producing 3250 lumens, total watt 320W, 80W lower but we need a micro management... 3.6YTL each lamp... (3USD).

The Law of Diminishing Light states that lamp uses its lumen value for every centimeter². 53,000 for 1cm², 13,250 for 4cm² and so on. 12inch is approximately 30cm, square of 30cm is 900cm²... 53,000/900 = 58,8~lm.

 

[massproducer]

12 inches? Don't we need a very good cooling system? And still we are using 9 fluorescent lamps, each producing 3250 lumens, total watt 320W, 80W lower but we need a micro management... 3.6YTL each lamp... (3USD).

The Law of Diminishing Light states that lamp uses its lumen value for every centimeter². 53,000 for 1cm², 13,250 for 4cm² and so on. 12inch is approximately 30cm, square of 30cm is 900cm²... 53,000/900 = 58,8~lm.

I can get my 1000 watt HPS's in 6" cool tubes within 12" of my plants canopy. So with proper venting, I 400 should not be too hard to keep within 12 inches.

The law of diminishing light works with feet not cm, at 1 foot there is no light loss.

At 2 feet, you would recieve 1/4 of the output, at 3 feet 1/9, and 1/16 at 4 feet. The light diminishes by the square of the distance

 

[ChatNoir]

I can get my 1000 watt HPS's in 6" cool tubes within 12" of my plants canopy. So with proper venting, I 400 should not be too hard to keep within 12 inches.

The law of diminishing light works with feet not cm, at 1 foot there is no light loss.

At 2 feet, you would recieve 1/4 of the output, at 3 feet 1/9, and 1/16 at 4 feet. The light diminishes by the square of the distance

This is getting interesting, I have made a short research and did not find any data indicating 1 foot or 1cm, so I am assuming 1 foot.

Our MH lamp is one foot away, so 53,000 lumens fully hits the canopy. Our one single fluorescent lamp is 3cm away, which is 1/10 foot, lets square it 1/100 and divide 3250 by 1/100 3250/(1/100) and we get 325,000 lumens. More input than output... We assume it is lumen value so producers calculated it is effecitivity at 1 foot so we get actually 6 times more lumen.

That is with single 36 watt fluorescent lamp, against 400W MH, using 10 lamps will make it 60 times more effective.

If I have made a mistake in calculation please do correct me.

 

[massproducer]

That is not how it works...The Law of diminishing light is saying that you don't loose any light until you reach 1 foot, and this is how much you loose there after. You can not get more light from a light then is input.

Also I would not say that fluoro's and HID's work based on the same laws being that they are totally different technologies.

The Law that I quoted is for HID's, but with CFL's or fluoro's you have to keep the light within a few inches inorder to recieve the stated output

 

[gettinggray1964]

good post

 

[ChatNoir]

That is not how it works...The Law of diminishing light is saying that you don't loose any light until you reach 1 foot, and this is how much you loose there after. You can not get more light from a light then is input.

Also I would not say that fluoro's and HID's work based on the same laws being that they are totally different technologies.

The Law that I quoted is for HID's, but with CFL's or fluoro's you have to keep the light within a few inches inorder to recieve the stated output

Any documents or citations that we do not lose any light untill one foot? If that is so, I have learned something new.

Because so long as I know, light makes an arch from the point of origin. This law is used a great deal in photography.

 

[massproducer]

get any Cannabis grow book

Here's a link that you can read more at, look at page 25:

http://books.google.com/books?id=rn...=X&oi=book_result&resnum=2&ct=result#PPA21,M1

 

[massproducer]

Because so long as I know, light makes an arch from the point of origin. This law is used a great deal in photography.

I am not sure what this has to do with anything, light can not be refracted until it hits something, but even with it being refracted by particles in the air, that has nothing to do with the lights intensity or the Law of Diminishing light???

 

[massproducer]

Here is more on grow lights in general

http://en.wikipedia.org/wiki/Grow_lamp

 

[ChatNoir]

get any Cannabis grow book

Here's a link that you can read more at, look at page 25:

http://books.google.com/books?id=rnwwxoOb3gUC&pg=PA20&lpg=PA20&dq=HID+distance+chart+hps&source=web&ots=6hPJkVEAiq&sig=vpijAoP__qkc6y88Q3qBGfKPlWo&hl=en&sa=X&oi=book_result&resnum=2&ct=result#PPA21,M1

It says 1 lumen is the equvalent of light that one candle sheds light to one square foot of area which is 1 foot away from the source. The closer we get to the source, the more light we get. Nothing different than what I say.

Though now, an idea popped up... People can cool CPUs with nitrogen coolers so why can't 400W MH can't be cooled? Keeping it 10cm (1/3 foot) away from canopy will increase it's lumen for 9 times!

Light is light and it is a cone, the book you have sent me says the same as well.

Do you have a camera? If so we can make a small comparision. All cameras give same values for same aperture and same iso values at same lumen. We can compare our values.

Note: It is important for photographers because we work with lumen as growers work.

 

[massproducer]

Here is what you said:

Our one single fluorescent lamp is 3cm away, which is 1/10 foot, lets square it 1/100 and divide 3250 by 1/100 3250/(1/100) and we get 325,000 lumens

I do not agree, what I read it saying is to try and keep your light within 12 inches if at all possible.

HID's can be cooled. I use a cool tube, to air cool my lights. The other thing is that there is a point at which plants can not recieve any more light and will start to display a break down of chlorophyll, like equtorial sativas do.

Either way my point is that fluoro's are not as efficient or effective as HIDs, unless your are sprouting seeds or cloning cuttings.

 

[ChatNoir]

Thanks for the information, I will keep that in mind and try and see, if it breaks down or if it blooms. I have bag seeds, what can I lose?

And thank you for your patience.

 

[camcam]

WOW, now that was a good debate! am going to read this again to get my head round it all, lol