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Calculation of Lumens/in, Lumens/ft

G

Guest

It has come to my attention that lumens per square foot and lumens per square inch can be calculated in different ways.

I've recently encountered the following problems determining Lumen/square inch.

People have two different methods for calculating the square footage of a rectangular cab.
1.) You determine the square footage by determining the surface area of each side and add them up.
2.)You can take the surface area the of cab floor only.

The following posts describe the problem

GVSB said:
I'm going to put myself out here and be a man about this....

Dr. BudGreenGenes...You say that your cab has "45.13 lumens per square inch." There are 144 square inches in 1 square foot. 45.13*144=6498.72 lumens per square foot.

Let's now look at your cab. You say that it is 24'' x 14'' x 28''. This is the standard way of saying 24 inches by 14 inches by 28 inches.

The surface area of a rectangular prism can be determined by the formula; Surface Area= 2*length*width + 2*length*height+ 2*height*width.

Given your measurement let's allow; length=24; width=14 ; and height=28

The Surface Area=(2*24*14)+(2*24*28)+(2*14*28)=2800 square inches or 19.45 square feet.

Based on your calculations you claim to have 45.13 lumens per square inch.
Your cab (dimensions provided by you) has a total of 2800 square inches.
The total lumens within your cab can be determined by multiplying total square inches by lumens per square inch.
Total lumens= 2800*45.13=126324 Lumens.

If I divide 126324 lumens by 19.45 square feet; 126324/19.45= approximately 6500 lumens per square foot
as determined earlier.

Now you seem to imply that you have only 5 lights in your bud box pg.3 post 36

and pg. 7 post 95 responding to krly.

If I divide total lumens by the number of lights then I will get the average number of lumens per bulb. Again, total lumens=126324 and you have five bulbs; thus, 126324 lumens /5 bulbs= 25264.8 lumens per bulb

I don't know how many lumens the ES42's have but I'm sure it is less than 25264.8 lumens.
Click to expand...

knna said:
Brother, you are confusing yourself with your own numbers.

Its obvious that 24" (2ft) x 14" (1ft 2") is just a bit more than 2 sq ft.

24"x14"=336 sq inchs /144 sq in per sq ft=2,33 sq ft.

45,13 lm/sq inch * 336 sq inches=15163 lm. He has 5 42w CFLs, so each CFL emits 15163/5= 3032 lm.

Roughly 3000lm for each 45w CFL, around the typical 65 lm/w of CFLs.

And that isnt low light levels, i use still less (19200 lm in 5 sq ft).
Click to expand...

Therefore, the amount of Total lumens determined with Dr.BudGreengenes estimate of 45.13 lumens per square inch is significantly altered depending on the method used to determine square footage (surface area of the cab).
Knna used method (2) floor surface area, and GVSB used method (1) cab surface area.

If a clear standard for measuring lumens/square foot is not used then the minimum amount lumens/square foot required cannot be determined.

What is the standard formula for measuring lumens/square foot?
Thanks...
 
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facelift

facelift

This is the money you could be saving if you grow
Veteran
I believe that the lumen rating of the bulb is equal to lumen per square foot. So a 1600 lumen bulb will produce 1600 lumen at one foot. Once the light travels farther than 1 foot the amount of lumen decrease. Remember that lumen are radiated from a light in 360 degrees so if you use a reflector to concentrate light in any single direction, you are increasing the number of lumen per square foot. I can't give the value, but it can't be all that much since the light 1st has to travel up to the reflective surface and then back down to the target area.

The reason I believe is from what I read from a search online for "lumen per square foot". From the diagrams I saw and the way the info was written, a candlefoot is equal to 1 lumen. That is a candle produces 1 lumen at 1 foot. The pages didn;t go into the size of the candle, nor did it mention that it matters.
 
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G

Guest

I've never known anyone to include the walls in their square footage. It's understood that the "floor" is the only plane that is calculated for the "square footage" in a typical garden.

L (in inches) x W (in inches), divided by 12 will gives you area in square feet, divided by 144 will give you area in square inches.

Divide the number of available lumens by your area and you get lumens per inch2 or per FT2.
 
G

Guest

"Lumens" are meaningless in regards to plant growth/biology. Photon production across the spectrum is important. People need to dump the word lumens and move on.
 
DrBudGreengenes

DrBudGreengenes

Well-known member
Veteran
QUOTE=Azeotrope]"Lumens" are meaningless in regards to plant growth/biology. Photon production across the spectrum is important. People need to dump the word lumens and move on.[/QUOTE]

So now you will now be providing the "Class" with Photon Production #'s for each HPS bulb,MH Bulb, and most common Flors?

I did not think so..... :bashhead:
Bcuz that info is NOT available to the GP.....But "Lumen's a universally accepted unit of light measurement" is available to the "Common Man"
Stop tryin to sound so "Smart" and give the guy some info that he can use
:spank:
 
S

Smoke68

Active member
LOL!!!
Funniest thing off all... SIMPLE MATH!!!!
So just to get this clear;
B(base)
W(width)
H(height)
SQUARE footage is base x width
CUBIC footage is base x width x height
Lumens per square foot is (base x width)/Lumens
Lumens per cubic foot is (base x width x height)/lumens
^^NOT THAT DIFFICULT^^
 
J

JackOneill

Member
Azeotrope said:
"Lumens" are meaningless in regards to plant growth/biology. Photon production across the spectrum is important. People need to dump the word lumens and move on.
Click to expand...

Great point cause too many people get caught up in the lumens when that doesn't matter much to the plants at all. Reason CMH does so well with less lumens than an HPS. IT puts out a better spectrum period.
 
cfl...KING

cfl...KING

Listen my username is from 07 lol
Veteran
24" x 24" floor space is 4 sq ft or 576 sq in, say we have 40,000 lumens, thats 10,000 lumens per sq ft (40,000 divided by 4 sq ft=10,000) or 69.44444continued lumens per sq in which equals 10,000 lumens per sq ft (69.44444continued x 144= 10,000). i dont know what you did but its the same thing either way lumens per sq ft or lumens per sq in. KING
 
G

Guest

DrBud-

Lumens is a measure of what we as humans see. It means absolutely dick to plants and is missleading to growers. You suggest that I give him some information that he/she can use. Good point. Hear it is: Study, look for spectrum graphs online and get the fullest (strongest across the spectrum) output bulb you can and put as much of that light as you can in your space. Strive to duplicate sunlight as best he/she can.

So get your fat, green type the F' off the screen. Do not try to "bark" at me as you obviously don't know shit about plant biology and lighting. What registers a large lumen value is the orange/yellow areas where HPS bulbs spike. Go study, read the CMH thread (every page and every word) and read other material. Anyone that uses lumens is living in the past. Anyone that uses HPS by choice doesn't know shit about plant lighting. You have pissed me off so FUCK YOU! :spank:

Azeotrope
 
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S

Smoke68

Active member
On a happier note... wouldn't it be better if we all just went to our own rooms and f***ed ourselves?
MOVING ON...
In a world where we see life in lumens, it is hard to imagine any other way. But lets try to imagine you are a plant... You cannot "see" how bright an object is, but you can see the spectrum the light gives off. Which brings me to CRI.
CRI; A rating system that indicates how colors appear under a given light source (lamp) on a scale of 100. The higher the CRI number, the more accurately the object’s color will be represented. The lower the CRI number, the less accurately it will be represented.
With this said... a bulb with a rating of 100 CRI with only 5 lumens of output, is NEVER going to grow a plant... but a light with 100 lumens and a CRI of 5, will at least be able to grow the plant.
For example, a standard shop light HPS has a rating of about 35 CRI... A standard MH has a rating between 65-75 CRI.
While HPS is far more inefficient, it is still the standard. At this point in time, HPS is the cheapest and most easily replaced.
 
G

Guest

What a joke that last post is. What a waste of time. I try to offer some useful and correct information here and I have to put up with that junk. Again, the claim is made that a bulb with more lumens will do more to promote plant growth. What a F***ing joke. That argument is absolutely laughable. To tell you the truth CRI has very little to do with it. What counts is photon production across the spectrum and R/B ratios. Lumens does not indicate anything related to potential to promote plant growth. It measures light that is largely unused by plants.

Honestly, I have been impressed with some of the micro productions on here. Largely the micro grows that use flouros. I wonder why? Maybe because most flouros do better across the spectrum. Lots of plant hormone production, root growth, resin production, node spacing and other biological functions are regulated/stimulated by differing parts of the spectrum. Most not affected at all by the area that gives "lumen" #s. Get it right or get out is how I look at it.
 
cfl...KING

cfl...KING

Listen my username is from 07 lol
Veteran
hey Azzhole chill out! r u 12 or sumthing, stop the negitive talk. reply with respect...Everyone

We have seen what Drbud can grow, which is dam amazing, were can we find your grows??? not everything is learned through books, experince is everything.
 
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S

Smoke68

Active member
Did I EVER say that CRI was EVERYTHING???? No, even I as a cheap, small time micro grower mix spectrum's, bulb types and shades depending on conditions and needs of the plants.
I am glad that the last post was such a waste of your time... that you bothered to wrote two paragraphs about it! LAUGH OUT LOUD! AT YOUR FACE! but you will never be looking me in the eye... STARE AT MY FEET BI*CH OR I AM KNOCKING YOU THE **** OUT!
I will not stand for your 16 year old attitude. Grow up. How dare you criticize me! I know about spectrum, CRI the temp bulbs burn at, so don't talk down to me!
BTW HPS has a decent spectrum for flower, just not a good CRI;)
Until you learn some respect, and start paying for my lighting... I am going to stick with my 75 WATTS per square foot however I want. You can stay stuck with your head up your Aze the way it is;)
Have a great day!
 
G

Guest

IMO, much of this debate stems from those who haven't figured out the difference between square measurement and cubic measurement. (shrug)
 
G

Guest

HPS has a crappy spectrum period. It was worth the two paragraphs to keep newbies (like yourself) from getting junk info fed to them. There is a ton of the spectrum missing with even the best HPS. The blues, UV, and far red. All of which stimulate important plant hormone and growth responses straight through the end of flower. Far red (infra red) helps to regulate growth and stimulate good strong stem growth. The UV in you are missing with an HPS is critical for stimulating full potential resin production. The blue end helps to keep stretch to a minimum. I would think that the micro grows would benefit in a huge way from reduced stretch?

So, I will leave you all alone to your outdated beliefs and methods. I will go back to my little world of full spectrum CMH lighting (that is available in virtually all sizes for all grow types) and continue to help out the folks who want to learn.

I do have a gallery for viewing. Someone asked where my grows are at. Start at my gallery. Check the CMH thread in the designs/equip thread and you will see that I not only know my shit front to back and back to front, but I know enough to know that ya'll are way behind the times if you are even O.K. with HPS.

Sorry this got so hot, but I am the one that got jumped when trying to stear someone down the path of fact in regards to lighting.
 
J

JackOneill

Member
either way you want to slice it CMH rocks it over anything right now period. Many results speak for themselves, the plants look more like outdoor plants under the CMH bulbs. I agree with azeotrope but I disagree with the bickering as that was uneeded by both parties. Chill out and smoke a phatty fellas. :rasta:
 
S

Smoke68

Active member
Phatty smoked, and settled down...
I now see I was wrong about CRI, lumen's and the effects(or lack there of) in terms of botanical needs.
Sorry about before mentioned arguing. It would seem I would have been one of the disbelievers of of around world, shadowed in the dark of a global Earth.
As I was saying previously in a "revised and toned down version", I DO NOT, and DID NOT deny the fact that in the botanical world of lighting the order, in descending order are incandescent<HPS<CFL<FL<MH<CMH. I was stating, that with COSTS AT HAND, HPS is the more efficient bulb, not in spectrum, CRI, lumens, "photons" or other what not, but rather in light output per watt and in cost to purchase.
Much of what I had been told in regards to bulb information, came from my seasons in local nurseries, so when somebody comes along talking about "round earth" ideas, I tend to misunderstand and speculate against unjustifiably.
With all the arguing that had gotten under way, we skipped over the whole basis of this thread.... So if not lumen's per square foot or inch, what unit of measure should be utilized?
 
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