The Basics Of Plant Lighting

Maybe you guys can help me with something I just can't seem to get my head around.

I'm trying to figure out how much light my plants are getting in veg. I run 6 - 23 watt CFLs over each 6 gallon pot, roughly one square foot. Lumen output decreases over time, but they start with 1400 or so each x 6 = 8400/sqft, kinda high. But ... I run them at 2 inches above the canopy. So, with the inverse square law ... um ... that's a LOT of lumens. I've looked around, and I still don't exactly know how lumens are measured. I think it's at 1 foot distance. Am I right, or am I confusing lumens with foot candles, or does it even matter? Anyway, if so, and mine are 6 times closer than that, then that's 36 times the lumens = 302,000 lumens/sqft - a ridiculous number. Huh?
 
Lumens measure the amount of light energy output by a light source. Foot-candles and lux measure the intensity of light falling on an object with a foot-candle being equal to 1 lumen/sq. ft. and a lux being equal to 1 lumen/sq. m. (1 foot-candle = 10.76 lux) So to determine the actual amount of lux/foot-candles hitting a plant you would need a light meter and take readings at various places around your plant. However, that seems a little overkill to me for growing weed so I'll just stick to wattages and lumens. Plus it gives us all a common basis in which to discuss varying light sources and their impact on growing cannabis.
 
:cheesygrinsmiley: And you didn't even get into the PAR lecture, heheh.

So, in terms of lux, are my calculations correct? I get 36 times the lux if the lights are 6 times as close?

There seems to be something wrong with the whole idea, and I can't pin it down. Any chance 138 watts of CFLs at 2 inches is "too much"?
 
First and foremost, lumen is a poor measurement for plant lighting. It is a measurement of brightness to the human eye and skewed to the 525nm wavelength, giving less weight to the wavelengths used most by plant photosynthesis (the upper and lower reds and blues respectively). Secondly, the inverse square law is not a perfect calculation when moving in closer than one foot (though it will give you a very close evaluation). As for there being too much light, with CFLs it is nearly impossible to hit the photon saturation point due to the phosphors used to create the color blend and the number of wavelengths hit. The more likely scenario is that they get burnt from the heat or dry out. Are you getting the most out of your lighting? Probably not. It does seem a bit excessive, but as long as the plant is covered well, you should be fine.
 
Thanks, Hosebomber. I'm just trying to get an idea of scale. 300,000 seems so wrong.

But I only get issues when the lights get closer than 2 inches - plants seem to like it just fine.

I'm trying to figure out why my plants barely stretch when they go into flower, and thought maybe light is part of it. Dunno.
 
If they are getting a high enough concentration of photons in a very high intensity (such as being 2 inches from the point source) they won't stretch much. The stretch comes from photo receptors sensing long wavelengths of red that come with the fall and shading from other plants. The growth is to put the flowers high to spread the seeds further. When they are receiving all of the light they need there is little incentive for them to stretch.
 
That gibes with my vague thoughts. They've been spending 2 months in veg under the close intense CFLs, and then they go into a room with 35 watt/sqft of HPS and don't stretch. If I'm thinking straight about the CFL intensity, they apparently get less light when they hit 12/12.

... I run a few 2700K CFLs in the mix - would it be better to remove those?

I'm trying to compare the pros and cons between 400 watts of CFL vs watts of HID. One can't be within 12 inches of the plant - the other can be 2 inches away, 6 times as close. It seems intuitive to switch to HID, but I get nicer node spacing with the CFLs. Isn't HID or LED a clear winner, except that both have to be kept far from the plants?

So I get confused about the inverse square law.
 
so has any one worked with a multiple bulb (hps and cmh) set up, perhaps someone knows of some journals they could direct me to
 
Start with Icemud. He's had CMH/HPS for quite awhile - moving to LED now.

Have you seen the long dual cooltubes? Groovy idea.
 
Thanks graytail
I am also interested in high brix gardening (more for food) but a spot on reference for me.

I have looked at the cool tubes but feel that the growzilla hood may suit my needs better. My space is 6x6x8 and two hoods with four 4hundred wt lamps should be doable considering heat issues. I also have a light mover which would give me even better coverage and only moving the hoods a foot or so back and for as well as different angles into the canope.

still looking for info on strength of light vs. par range(i.e.600w hps vs. 400w high par) and does the cmh bulb rate as a high par?
 
All good questions for Ice! :cheesygrinsmiley:

He was quite an advocate for CMH in some of his threads. He usually checks in every day or two. Heck, PM him.

:thumb:

1600 watts over 6x6 should do it, especially with movers, heheh! I'm considering adding a 400 watt to my 600W hps in a 4x4. The cooltube would be ideal for me.
 
Very interesting thread. I am building out this first grow setup right now. So far the veg shed of 8x6' is built out it has X2 1000 w MH with sealed and exhausted hoods powered by adjustable ballasts(may change one of the MH to HPS..) also have an HO t5 hood for the babies and seedlings. The plan was to setup one 1000 light on one end for plants around a foot and the other lights for teens and mothers. Will be using the Green Lantern Routine lighting regiment for veg and diminishing flower. organic, teas, super soil and hempy hydro buckets so I am running two grow styles one hydro and the other soil first time out to bat.

Clones are coming in next week. skywalker og, blue dream and probably some tahoe og.. Was going to try out some SOG to help get the flowering room dialed in asap and keep the rest to veg for a few weeks.. Plan to harvest every couple of weeks.

Flowering room has most parts picked up just need to build out the rooms(x2 5x10x8.5') stick frame 2x4, insulated and ducted. Each enviro is sealed from the other and can add a third and fourth 5x10 if needed down the road..

So I was fixing to run X2 1000 HPS sealed on XXXXXL type hoods plus on a light mover per 5x10' but might go ahead and make up some more floor supplemental from like cfl's or cheap led. Figure to run these on the floors, in between rows of pots and possibly around the perimeter of each grow room. I also pondered adding a third 1k light per booth but I think lower and side would cost less per month to run over the long haul but lmk what you think! Right now, I have tons of 1k lights that are on huge sealed ducted hoods here ready to go but would be buying any cfl or led fresh.. Which is better in a 5x10 box? X3 1kw hps or X2 hps and a bunch of under the canopy and side wall lighting..? Is this a question even answerable.. lol probably not.

I would love to make a tuned LED strip light that did the spectrums.. A light that would roll out flat and would run through the canopy and mount on the walls.. Kind of like xmas lights in your tree and home..

This is my first post. Have found much great info out from the forum and I hope to learn and input more as time goes on. Looking forward to starting up a grow journal in the next week or two. The design of the grow is based on the parts I came across and what I have been reading mostly from this forum.

I think it would be cool to make a pontoon such as the igro pontoon for my hoods... Someone here with the time should make a batch of pontoons to fasten on a regular hood I would be a buyer!

I think it would be baddass to add the 740 red and 480? blue type spectrum LED on an HPS hood... Like you could have 1k hps or halide plus 1-200 leds installed and relflecting though the sealed hood, inside of the reflector of hood... This would let you power both light types off of 1 power supply......................

LED and HPS installed in one reflector would look clean imo. Less wires and stuff hanging in the air..

Appreciate all of the good knowledge on here. Some of y'all were growin before I was born so keep it up I love to learn from pros!

breeZee
 
ok.... I am just not getting why so many people are still so concerned about Watts. watts are the measurement of how much power it uses to run the bulb. in the past- sure that made a difference because the more watts(power used)- the brighter the light(incandescent world), but with cfl's and LED's it doesn't work that way anymore. the numbers to be concerned about are lumens and the kelvin range.
 
Periwinkle, please read over this thread again. Lumens are not a good measurement for plant lighting by any means. They are skewed to rate wavelengths of 525nm and those in the green range higher than any other wavelength. Therefore the light that does the least amount for growing gives you the highest lumens. Kelvin range only matters when we are talking about white light. If you are using a discrete diode, you will not have a kelvin black body temperature to read. Watts are currently the best standard to use because the companies are not likely to give you the scientific breakdown of each of their diodes or CFL bulbs. We can make some basic assumptions when making the calculations with watts and any current type of lighting. When we do this we have a very close guesstimate of actual radiant flux (true power, in photons, being produced by the light source).
 
direless said:
Thanks graytail
I am also interested in high brix gardening (more for food) but a spot on reference for me.

I have looked at the cool tubes but feel that the growzilla hood may suit my needs better. My space is 6x6x8 and two hoods with four 4hundred wt lamps should be doable considering heat issues. I also have a light mover which would give me even better coverage and only moving the hoods a foot or so back and for as well as different angles into the canope.

still looking for info on strength of light vs. par range(i.e.600w hps vs. 400w high par) and does the cmh bulb rate as a high par?
Click to expand...

I saw a recent test that was run between CMH, a few models of LED, HPS and MH and CMH actually had a better PAR value than all of them. CMH bulbs rock and if it wasn't for LED being much cheaper to run, I still would be running CMH. I wish they had an LED that output the spectrum of CMH, I would be one happy grower!
 
direless said:
Thanks graytail
I am also interested in high brix gardening (more for food) but a spot on reference for me.

I have looked at the cool tubes but feel that the growzilla hood may suit my needs better. My space is 6x6x8 and two hoods with four 4hundred wt lamps should be doable considering heat issues. I also have a light mover which would give me even better coverage and only moving the hoods a foot or so back and for as well as different angles into the canope.

still looking for info on strength of light vs. par range(i.e.600w hps vs. 400w high par) and does the cmh bulb rate as a high par?
Click to expand...


Here is the video of the test of Par values for CMH, HPS, and led.
[video=youtube_share;yVMbxqddkFU]
[/video]
 

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