# What is your lumen goal?



## jackson1 (Jan 31, 2010)

Cervantes talks about 10K lumen's per SQFT. and i hear others talk about 5,000 for flowering. What are you comfortable using if using HPS? 

I have a 2'D x 4'W x as much as 8'T space if i want it. I was thinking of building a small veg cabinet on the bottom 2'W x 4L x 18" tall which will still leave 6' 5" of height so I don't know?


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## pcduck (Jan 31, 2010)

I strive for 5000+ lumens/sqft  in flower


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## Old_SSSC_Guy (Jan 31, 2010)

a 400 watt would light it well. the veg space seems small...


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## ozzydiodude (Jan 31, 2010)

I try to maintain 3000 lumens in the veg area and 5000 lumens in the flowering area I usually clone under 2000 lumen til I see roots then they get moved to the veg 3000 lumen area


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## MindzEye (Jan 31, 2010)

5k lumens per square foot is the minimum Ill run.. Running 7550 for flower right now... Veg is 5800 per foot


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## jackson1 (Jan 31, 2010)

Old_SSSC_Guy said:
			
		

> a 400 watt would light it well. the veg space seems small...



Actually, I'm not speaking correctly. The area is really for starting seeds or even clones in the future and once they are good and started i will move them up top to finish veg and flower them when ready. Basically, this space would allow starting seeds or clones 2-3 weeks before each harvest.


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## Old_SSSC_Guy (Jan 31, 2010)

then you're right on the mark jackson... heh...  

i've never been able to think of delivered light in a lumens measurement.  to me a plant will be as big as 4-5 foot tall.  the lumen output at the lamp seems radically different than those delivered 4+ feet below the lamp - or within the space uniformly.  more power to those who can measure such things consistently - they probably get better returns than me!  i think in wattage and square feet.  maybe because the math is easier for an old stoner.  i am easily confused by big numbers... heh...

cool growings to you. 




			
				jackson1 said:
			
		

> Actually, I'm not speaking correctly. The area is really for starting seeds or even clones in the future and once they are good and started i will move them up top to finish veg and flower them when ready. Basically, this space would allow starting seeds or clones 2-3 weeks before each harvest.


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## jackson1 (Jan 31, 2010)

Old_SSSC_Guy said:
			
		

> then you're right on the mark jackson... heh...
> 
> i've never been able to think of delivered light in a lumens measurement.  to me a plant will be as big as 4-5 foot tall.  the lumen output at the lamp seems radically different than those delivered 4+ feet below the lamp - or within the space uniformly.  more power to those who can measure such things consistently - they probably get better returns than me!  i think in wattage and square feet.  maybe because the math is easier for an old stoner.  i am easily confused by big numbers... heh...
> 
> cool growings to you.



You are right on there, there is a huge difference in lumen's received depending on how far from the plants, no question there and you're right, that is the tricky part. 

So then how many watt's are you personally looking for when growing? veg and flower.


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## monkeybusiness (Jan 31, 2010)

I aim for 7500 in the flower section


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## leafminer (Jan 31, 2010)

I run about 6,800 L/ft sq but I'd like more. 10K/ft would be great. I think intensity wins over duration. My plants getting 6 hours of natural sunlight in the greenhouse and 6 hours of daylight do lots better than when they're in the growroom getting 6.8KL for 12 hours.


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## Old_SSSC_Guy (Jan 31, 2010)

i know it sounds dumb, but i used the same logic for selling grow lights for so long that i'm numb and generally clueless about about lumenosity anyway:

2'x2' = 150 watt
4'x4' = 400 watt
6'x6' = 600 watt (better to have 1000w)
8'x8' = 1000 watt

anything bigger i just add more 1k lights, and i double the wattage for flowering.  no calculator required, just blind ignorance based on experiential lumens... heh...  when asked "how much light do i need?" i say "more".

even better is my oh-so researched technical & scientific logic applied to the question of when to replace HID light bulbs (i do it 2nd or 3rd crop under the same lamp):  "replace the bulb when that sucker just don't look as bright as it used to".  




			
				jackson1 said:
			
		

> You are right on there, there is a huge difference in lumen's received depending on how far from the plants, no question there and you're right, that is the tricky part.
> 
> So then how many watt's are you personally looking for when growing? veg and flower.


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## jackson1 (Jan 31, 2010)

Old_SSSC_Guy said:
			
		

> i know it sounds dumb, but i used the same logic for selling grow lights for so long that i'm numb and generally clueless about about lumenosity anyway:
> 
> 2'x2' = 150 watt
> 4'x4' = 400 watt
> ...



See, this is what i'm talking about, many people would consider that low for watt's and/or lumen's. 

Let's look at it: Example bulb is based on a 50,000 lumen 400 watt hps.

4'x4' = 16 sqft

400 watts/16 sqft. = 25 watts per sqft. 

50K lumen's/16 sqft = 3,125 lumen's per sqft. 

Most would say that is good for veg but not for flower and is far from what Cervantes talks about in the grow bible as being optimum lumen's per sqft. or even watt's for that matter depending on how you want to look at it, watt's or lumen's. I read where you want at least 50 watts per sqft. however, if you are able to obtian good results with half that why not use less? I guess there is no clear answer just like the rest of it. Way to many options and opinions i guess.

I actually remember now what he (Cervantes) about lumen's per sqft. The sun produces 10,000 lumen's per sqft. so i think that is the number he is saying to try and achieve, or the closer the better kind of deal.


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## ozzydiodude (Jan 31, 2010)

If you look at the charts below you can see what the lumen are for a given distance from the bulb.


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## jackson1 (Jan 31, 2010)

ozzydiodude said:
			
		

> If you look at the charts below you can see what the lumen are for a given distance from the bulb.



Actually, that chart is measured in foot-candles and therefore we are talking about lux but there is no direct conversion. They are physically different concepts.

Foot-candles are a measurement of light intensity - how "bright" is the illumination striking a particular object or surface. It is a measurement that is taken at a single point. If you have a large surface, you need to take a whole bunch of individual foot-candle measurements at different points in order to get an overall average. It is common to find foot-candle recommendations in the field of ergonomics and industrial engineering, where people need to be provided with adequate light to perform certain tasks. Foot-candle measurements obey the inverse-square law: if you double the distance from the light source, you will find the intensity is now 1/4 as bright. 

Lumens are a measure of total light output from a source. If you could take a foot-candle measurement at every single point in the entire beam pattern of a particular source, and multiply by the total area of the beam, you would end up with lumens. Distance from the source makes absolutely no difference.

It's all just confusing in the end.

I am looking at 9666 lumens sqft if I make my grow space 2'D x 3'W x up to 8'T. I'm growing autos so don't need a lot of space really. With reading about autos it sounds like they are very light dependent. Anyway, I'd just like to get as close to the 10000 lumen sqft number Cervantes says you should try and achieve.


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## ozzydiodude (Jan 31, 2010)

hxxp://www.theledlight.com/lumens.html
Lumens, Illuminance, Foot-candles and bright shiny beads&#8230;.

In defining how bright something is, we have two things to consider.

1. How bright it is at the source- How Bright is that light?
2. How much light is falling on something a certain distance away from the light.

Lets' do some definitions now&#8230;&#8230;

We're in America, so we are going to talk about units of measurement that concern distance in feet and inches. So, we will use some terms that folks in Europe don't use. We're going to talk about "foot-candles".

This one's simple. Get a birthday cake candle. Get a ruler. Stick the candle on one end of the ruler. Light the candle. Turn out the lights. Sing Happy Birthday to Doc. It was his 47th on the 23rd. OK, quiet down. Enough of that nonsense. One foot-candle of light is the amount of light that birthday cake candle generates one foot away.

That's a neat unit of measurement. Why? Say you have a lamp. You are told it produces 100 foot candles of light. That means at one foot from the lamp, you will receive 100 foot candles of light.

But here's where it gets tricky. The further away you move the light from what you want to illuminate, the less bright the light seems! If you measure it at the light, it's just as bright. But when you measure at the object you want illuminated, there is less light! A Physics teacher is going to tell you that light measured on an object is INVERSELY PROPORTIONAL to the distance the object is from the light source. That's a very scientific and math rich way of saying, the closer you are to the light bulb, the brighter that bulb is. Or, think of it this way. You can't change how much light comes out of your light bulb. So, to make more light on an object, you have to either move the light closer, or add more lights. 

Now, lets get to LUMENS.

A LUMEN is a unit of measurement of light. It measures light much the same way. Remember, a foot-candle is how bright the light is one foot away from the source. A lumen is a way of measuring how much light gets to what you want to light! *A LUMEN is equal to one foot-candle falling on one square foot of area.*

So, if we take your candle and ruler, lets place a book at the opposite end from the candle. We'd have a bit of a light up if we put the book right next to the candle, you know. If that book happens to be one foot by one foot, it's one square foot. Ok, got the math done there. Now, all the light falling on that book, one foot away from your candle equals both&#8230;&#8230;.1 foot candle AND one LUMEN!

Ahh, we've confused you. Let's split off from this and talk about the difference between RADIANCE and ILLUMINANCE. 

RADIANCE is another way of saying how much energy is released from that light source. Again, you measure it at the source. Unless you're talking about measuring the radiance of something intensely hot, like the Sun. Then you might want to measure it at night, when it's off.

ILLUMINANCE is what results from the use of light. You turn your flashlight on in a dark room, and you light something up. That's ILLUMINANCE. Turning on a light in a dark room to make the burglar visible gives you ILLUMINANCE. It also gives you another problem when you note the burglar is pointing your duck gun at your bellybutton.

Illuminance is the intensity or degree to which something is illuminated and is therefore not the amount of light produced by the light source. This is measured in foot-candles again! And when people talk about LUX, it's illuminance measured in metric units rather than English units of measure. To reinforce that, LUX is the measurement of actual light available at a given distance. A lux equals one lumen incident per square meter of illuminated surface area. They're measuring the same thing, just using different measurement units.

Pretend you're an old photographer, like O. Winston Link, or Ansel Adams. These two gods of black and white photography (and a print made by either can fetch quite a hefty sum of money these days) used a device called a light meter to help them judge their exposure. (There is another way of judging exposure-that's when someone whispers in our ear at a cocktail party, "You silly twit, your fly's come undone!").

These light meters were nifty devices. You could use it to show how much light was falling on an object, light from the sun, and reflected light energy from every thing else. Or you could use it to show how much light energy was reflected off the object itself.

All this brings back two points. Well, three.

The first point is if we measure the output of a light at the source that gives us one thing. 

The second point is that we use an entirely different unit of measure if we are measuring the results of that light's output.

The third point is the instructor is right off his trolley, isn't he?

Now back to the book at the end of the ruler.

We've measured two different things. We have a unit of measure for how much light is produced. We Yankees express that as a foot-candle. Being lazy, we use it all over the 
place.

More Confusion! Candlepower! 

Candlepower is a way of measuring how much light is produced by a light bulb, LED or by striking an arc in a Carbon-Arc spotlight. Is it a measure of how much light falls upon an object some distance away? No. That's illuminance. Is it a measure of how well we see an object that is illuminated by that light source? No. That's something all together different, and we are not going there!

Nowadays we use the term CANDELA instead of candlepower. Candlepower, or CANDELA is a measure of how much light the bulb produces, measured at the bulb, rather than how much falls upon the thing you want to light up. Further confusing the matter is beam focus. That's how much candlepower can be focused using a reflector/lens assembly. Obviously, if you project all your light bulbs intensity at a given spot, or towards something, it will be more intense, and the illuminance will be higher. 

And here comes the confuser! A candlepower as a unit of measure is not the same as a foot-candle. A candlepower is a measurement of the light at the source, not at the object you light up.

And a candela is the metric equivalent of the light output of that one candle, based on metric calculations. And since using a candle is rather imprecise, the definition was amended to replace a light source using carbon filaments with a very specific light source, see the following:
The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. 

The above from the National Institute of Standards Reference on Constants, Units, and Uncertainty.

Candlepower is a measure of light taken at the source-not at the target. Foot-candles tell us how much of that light is directed at an object we want to illuminate.

Now, lets convert the lumens, a metric unit of light measurement, to candlepower.

We understand a candle radiates light equally in all directions, its output, in this consideration is not focused by any mechanical means (lenses or reflectors). Pretend for a moment that a transparent sphere one meter in radius surrounds your candle. We know that there are 12.57 square meters of surface area in such a sphere. Remember your Solid Geometry classes?

That one candle (1 Candlepower/Candela) is illuminating equally the entire surface of that sphere. The amount of light energy then reflected from that surface is defined thusly:

The amount of energy emanating from one square meter of surface is one lumen. And if we decrease the size of the sphere to one foot radius, we increase the reflected energy 12.57 times of that which fell on the square meter area.


LUX is an abbreviation for Lumens per square meter. 
Foot-candles equal the amount of Lumens per square feet of area.

So, that one candlepower equivalent equals 12.57 lumens.

And for you figuring out LED equivalents, first you must know how many lumens your LED's each produce. Then divide that value by 12.57 and you have candlepower of the LED. You don't have foot-candles, remember foot-candles are illuminance. And we are measuring radiance.

Summing it all up:

Candlepower is a rating of light output at the source, using English measurements.
Foot-candles are a measurement of light at an illuminated object.
Lumens are a metric equivalent to foot-candles in that they are measured at an object you want to illuminate.
Divide the number of lumens you have produced, or are capable of producing, by 12.57 and you get the candlepower equivalent of that light source.

We've now converted a measurement taken some distance from the illuminated object, converted it from a metric standard to an English unit of measure, and further converted it from a measure of illumination to a measure of radiation!

This has been an ideal proof of the superiority of the metric system. Then again, the metric system is a product of those wonderful folks that brought us:

Renault, Peugeot, Citroen, and Air busses. Not to mention simply awful Bordeaux.

And, if you're happy with this, send those little gems to:

Robert H (Doc) Bryant
3408 Thomas Ave
Midland, Texas 79703-6240

I hope you have enjoyed this as much as I have. You ought to see me up in front of a classroom. My classes are absolute laugh riots. But people learn!


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## jackson1 (Feb 1, 2010)

say what? lol.......

I think i will just have a 10K lumen sqft goal at least with HPS. the closer the better. I will have 6333 lumen's under MH and 9666 lumen's under HPS for flower initial lumen's and if i can't do it with that i cant do it at all.


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## MindzEye (Feb 1, 2010)

Jackson, look at my grow journal in my signature, the Purple Kush, headband and WW grow.. That is with a 400w in a 2x4x7 grow tent. If I had put a 600w in there I would have needed to buy some serious fans to keep it cool in the small space..


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## dirtyolsouth (Feb 2, 2010)

:yeahthat:

Yuppers...   I run a 1K hps and a 6 bulb 4' T5 in 8 square feet...:holysheep:  

It takes me running 630 cfm of fan power and a 6" cool tube to move the hot air out of there...   I bought a Quantum dimmable ballast with the intention of running it at 500w or 750w and I put in the T5 as a sidefill light... I never thought that I could keep temps in the mid 70s running it at 1K in a 2 x 4 x 8 closet but low and behold:   W-h-o-o-o-o-o-o-o-o-o-s-h~!  In the summer I have to use a window a/c unit in that bedroom but as long as I keep temps around 70 in the bedroom I can run 175K lumens and keep things around 75º no problem with a passive intake...  It comes out to a little under 22K lumens per square foot...:hubba:  I know it's overkill and I really_ should_ run it at a lower wattage and save a few bucks on power but between the 36" optimum penetration range of running it at 1K along how much *brighter* it is at max voltage makes it hard to drop the dimmer unless the temps start getting away from me.  I also love being able to get all my lower buds hard as a rock if I keep my plants around 40" or so high too...  As long as most of my buds are within a foot and 36" of my 1K they all get very well developed.  No scruffy budz.  The penetration power rocks.

Happy Growing!


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