The Basics Of Plant Lighting

Mcloadie, I just moved here less than a year ago and when I got here the guy next door came over, handed me a plant and said welcome to CA. So i grew it got a few seeds from it and so this is why I am calling it "The Dope Box Grow". I have started a journal with pictures of the plants and figured out how to post a signiture at the bottom, so I have been adding to it a little each day to keep track of things.
 
how about the new LED light bulbs..how would they work. I seen them at home depot. They are 60w bright white 3000k and a daylight 60w 5000k but only put out 800 lumens. They screw rite into any normal light socket. Or would a couple of cfl's might work better. Any advise would help??
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You, my friend, have a vast knowledge of lighting. Your article was as informative as it was confusing to us
'non scientist'. Maybe you could give us CFL users a manifesto on this topic. TY, and good light.
'
 
question regarding Lumens?

I have been told basically the more lumens the better, I know its not the end all be all, but why are we looking at something like 130k lumens for HPS, and around 11-19k lumens for LED. Simple math tells me that HPS is 10x better, but I know its not that simple. I am assuming that LED lumens might calculate differently
 
I think you must have me mixed up with someone else, I have no idea what you are talking about. I don't have the knowledge to know what you are talking about. Sorry.
 
Oh, now I remember. Your the guy that wrote that manifesto about lighting. That was a very interesting and way over my head piece of work. As a matter of fact, I was telling my brother, as well as I could, about this piece. Very impressive. I studied a little science at LSU, mostly math, economics, probabilty etc. and couldn't understand a fucking thing you were trying to impress on us underlings, aka, under and under under graduates. I very much appreciate the effort, but the result for most of us non genius's is pretty much wasted . Thank you for the effort ant the time, really.
 
There are a few factors in what you are talking about DD. First, you need to understand the definition of lumen and how it is calculated.

The following is from Wikipedia and a pretty good definition:
The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power (radiant flux) in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux measurements indicate the total power of all electromagnetic waves emitted, independent of the eye's ability to perceive it. A lux is one lumen per square meter.
The lumen is defined in relation to the candela as 1 lm = 1 cd·sr
A full sphere has a solid angle of 4·π steradians,[1] so a light source that uniformly radiates one candela in all directions has a total luminous flux of 1 cd·4π sr = 4π ≈ 12.57 lumens.[2]

Basically, a lumen is the brightness of a point source to the human eye.

Next you have to consider the inverse square law. Yes a 1000 watt HPS puts out a shitload of light, but it also puts out a shitload of heat too. You have to keep it at least 1 foot from the top of your plants to keep them from burning. A plant will receive the square root of the amount of lumens for every 12 inches you move away from that light source.

Next you have to factor in how lumens are measured. It is skewed to 555nm (green) light. Because this is the wavelength that humans see best. So one lumen from the red diode will actually put out 30-60% more photons than one lumen of 555 green led light. The same holds true for blue LEDs as well. However, the radio spectrometers are set to the lumen standard because that is how we have always measured light in science. So all LEDs are set to that standard too. On most manufacturers datasheets, you will be able to find the radiant flux value. That is the measurement I personally use in the design and development of my panels.

I hope that answers your question, If not please feel free to guide me to exactly what information you are looking for.
 
I am about to create two more grow spaces and I found this post very helpful as I am trying to figure out what lighting I should use. Sorry ahead of time for bumping an older thread.

My question is this- According to your post, CFLs require 65 watts/sq ft for flowering. A 4' by 2' T5 that has 8 bulbs at 54 watts each will only produce 432 watts, over a space of 8 sq ft. You say it would need a total of 520 watts (8sq ft X 65 watts) minimum for adequate production. Are you saying that this T5 fixture won't put out enough light without supplementing another 90 watts with another light?
 
If my box is 5x2x2 using cfl lights. What is the right amount of watts to use ?

I have 8 cfl 100 watt daylight bulbs (energy used in watts 23) and 4 cfl bright white 100 watt bulbs (energy used in watts 23) is this enough for to get the best performance from my plants ?

If not how many more lights do I need?

I plan on growing 1 -2 plants in my box.
 
Your measurements do not seem correct. Is it 5' length x 2' width x 2' tall? OR is it 2' long x 2' wide x 5' tall? If it is the former, you will have sever height issues keeping a plant under 1' tall. If it is the latter, it will be much more manageable. In this case you are covering a 4 square foot area. If using CFLs I suggest 65 watts per square foot as per the second post. This means you need 260 watts of CFLs. So you would want to put 11 or 12 of the bulbs you currently have in that area. CFLs will cause a fair amount of heat in that size area.
 
I'm new here but following this thread and particularly Hosebomber's last reply about the 2'x5' closet (my space is a 2' deep x 5' wide x6' high closet) I will share what I have learned. That means I did it wrong the first time. I used CFL's 23W bulbs put together a light strip using bakelite pre-wired 4 bulb cluster sockets as they only cost $3.26 a socket. Built two sets at a cost of less than $40 including bulbs (I got a great source for 23W bulbs at $.50 each). As each socket has 4 bulbs 23W = 1600 lumen therefore 4x1600=6400 lumen and by attaching 4 sockets to a 4' board (1"x4") I have 368W producing 25,600 lumen per light strip. And they do put out some heat. As a matter of fact being a first time indoor grower on my first pass - I started my seedlings using an old 4' 40W T12 fluorescent tube fixture and they did fine even when I added a second 4' 40W T12 fixture in the closet for the next 10 days. At two weeks I put together my CFL fixture and found 1 fixture was way too much light and heat for the young plants. After totally stressing my little plants I cut back using only 1/2 of the fixture or 2 sockets (8 bulbs) and I re-started another set of seeds. It's all a learning process but I know I have enough light(s) as if I used both fixtures it would be 51,200 lumen in a 2'x5'x6' closet. Right now as the plants are still so little I can keep the door open and use a 16" oscillating fan for cooling but know I'll end up putting in at least a 70CFM exhaust fan at the top of the closet.
 
Here is my follow up to the previous post I did. Looking for guidance on next batch of seedlings and not wanting to do it wrong again. As I said; I started another batch of seedlings (9). I will list my plan and am looking for advice from more experienced individuals on this plan. Got to have a plan or you can't measure yourself...

18 on 6 off cycle till flowering week then 12 on 12 off

Week 1 - Start seedlings under 40W 4' double tube fluorescent fixture using 6500K/2325 lumen bulbs x 2 (4560 lumen starting point).
Week 2 - Add second 40W 4' double tube fluorescent fixture adds another 4560 lumen for 9300 total.
Week 3 - continue under 2 fixtures above (first three weeks T12 40W fixtures will be about 2" above plant tops)
Week 4 - transition to using 1-4 bulb socket (23W CFL providing 1600 lumen or 4 x 1600 = 6400 lumen). I know the CFL's are much more effective at producing light than the T12 40W tubes so while I'll be downsizing for a week in total lumen on paper in reality more light will reach the plants. Hang light fixture approximately 6" above plants first day and lower 1/2" each day till only 3" inches above.
Week 5 - add second (plug it in as I wired first two cluster sockets individually with their own power cord and last two together for when I need all four sockets on) 4 bulb cluster on plants.
Week 6 - rotate plants to other end of fixture turning on 2 cluster sockets (wired together 2) and turn on 3rd cluster socket; now using 12 bulbs or 19,200 lumen hitting plants.
Week 7 - half way through turn on 4th fixture increasing lumen up to maximum - or 25,600.
Week 8 - ditto week 7
Week 9 - switch to 12 on 12 off and change bulbs to all 2700K 23W - cut two clones per plant and identify them by number.
Week 10 - add second fixture in grow room switching on one cluster socket per week now (32,000 lumen)
Week 11 - switch on second socket second light strip (38,400 lumen)
Week 12 - switch on third socket second light strip (44.800 lumen)
Week 13 - switch on fourth socket second light strip (51,200 lumen)
Week 14 - Week 16 - full lumen light power at 51,200 watching buds grow
Week 17 - harvest

Any suggestions or recommendations please comment.
 
If i'm reading this correct you are using 36 23 watt CFL bulbs? That draws ~828 watts for 51200 lumens... Lumens is a horrible measurement of lighting for plants. However, you are using 228 more watts than an HPS and getting at a min 20k lumens less. Likewise, you are probably creating more heat than the HPS would as well. If your $40 per 4 bulb fixture holds true, that means you spent over $350 setting that up. You can get a 600 watt system cheaper than that, have less heat, better coverage, less power draw. Please correct me if I am wrong on any of this.
 
Hosebomber said:
Your measurements do not seem correct. Is it 5' length x 2' width x 2' tall? OR is it 2' long x 2' wide x 5' tall? If it is the former, you will have sever height issues keeping a plant under 1' tall. If it is the latter, it will be much more manageable. In this case you are covering a 4 square foot area. If using CFLs I suggest 65 watts per square foot as per the second post. This means you need 260 watts of CFLs. So you would want to put 11 or 12 of the bulbs you currently have in that area. CFLs will cause a fair amount of heat in that size area.
Click to expand...

Should I use all 12 lights from the beginning or start with 4 or 5 bulbs while the seeds are just babies an then add lights as it grows?
Remember I'm starting with two plants. Would all 12 be too much for the seedlings?

My box is 5ft tall 2 ft wide 2ft long
 
Hosebomber,
I spent less than $45 for both light strips for 32 bulbs and am using 23W bulbs. 4 bulb cluster sockets are $3.26 each X 8 (4 per strip) or $26.08 and the bulbs are $.50 X 32 or $16.00 or $42.00 total for the whole thing as I had the wood strips around just as multiple extension cords and wire nuts from having a retail store where we did Christmas big time in lights...Find me a cheaper set up if you can but doubtful. I did the wiring myself in less than 10 minutes (I did work in a development lab for electrical engineering at IBM). I forgot to add the 3/8 threaded nipples and nuts they were $.18 cents each..for 8 or $1.08 more. That's $43.16 total for two light strips each producing 25,800 lumen. The power company supplies the local Goodwill Stores with CFL's packaged 2 per box for $1.00...

Now you say lumen isn't a good measure but watts are. But both can be used as both are measurable. 23W CFL's typically produce 68-70 lumen per watt. So whether it's 5,000 lumen per sqft or 64W per sqft for flowering it's the same as having fifty cents with two quarters or 5 dimes; it's still fifty cents.

We got a storm coming it's dark outside so I'm signing off and shutting down the PC.
 
Based upon my experience I'd start with a minimal number of lights as you can as they are seedlings. My other post I tell how I produced both light and heat stress on my seedling using too many bulbs at the start.
 
Jeeztatted said:
Should I use all 12 lights from the beginning or start with 4 or 5 bulbs while the seeds are just babies an then add lights as it grows?
Remember I'm starting with two plants. Would all 12 be too much for the seedlings?

My box is 5ft tall 2 ft wide 2ft long
Click to expand...

Starting off with a couple of bulbs over each seedling and slowly increasing the amount as the plant grows is most effective, both in energy consumption and plant growth rates.
 
I misunderstood your construction methods/description and thought you where saying each 4 bulb cluster was costing you $40 to make. That's a good price for the amount of lighting you are getting. Depending on where you live, it will take at least 2 years for the power consumption difference between your set up and a 600 watt HPS system to make it worth while to switch.

There are a few things you need to understand about lighting and the measurements used. Lumens are described rather in-depth in this thread. Some of the things I didn't mention have to do with CFLs and how those lumens are calculated. If you look at 2 different CFL bulbs of 2700k rating and 6500K rating, you will notice that they both consume the same 23 watts of power. However the 2700k will produce ~100 lumens less than the 6500k. This is due to how lumens are skewed to the 525nm color range for brightness to the human eye. So the more green coloring in the light the higher the lumen count even though it actually produces the same or less number of photons.

Watts are a measurement of input power. While there is a correlation between the input power and the number of photons released, there are many other factors in play. The major factor being power conversion efficiency of the driver and efficiency of that type of lighting. We can make basic assertions (such as my 65 watts per square foot of flowering space with CFLs) because the differences in efficiency between manufacturers is so low that it makes nearly no meaningful difference relative to the output of that type of lighting.
 
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