Lighting Facts

[rebel dawg]

Here's something that may help the new grower understand the importance of lighting and encourage the experienced grower to experiment a bit.
Proper lighting is the most important ingredient an indoor grow. Photosynthesis and chlorophyll production occur throughout the spectrum with peaks in chlorophyll synthesis around 400nm in the violet wavelengths and photosynthesis around 700nm in the orange-red wavelengths. It's easy to see that any artificial light producing the visible spectrum can be used to grow plants. Only a few types of artificial lights will grow plants well.

Fluorescents and high intensity discharge (HID) lights have been the only useful artificials until the recent past when LED and MPS (microwave powered sulfur plasma) became available. The price of LED & MPS is still prohibitive for the grower on a small budget. Currently they are about twice the price of a dual 1000W system/bulbs/reflector/fans. However, LED's use much less energy and have a much longer life than HID and flourescents so their savings is realized slowly. MPS systems use 1000W of energy; they only offer savings in the less frequent bulb changes. MPS bulbs only need to be changed every 7 yrs while MH & HPS should be changed yearly.

Incandescent, halogen, and mercury vapor lights will grow plants, just not well. They produce a lot of heat and little light so they are much less efficient than the others. Their spectrums are heavily weighted on the red side which induces stretching (longer internode spacing). Heat also induces stretching which combined with the redder spectrum produces a spindly plant sparsely populated with leaves.

Lights are often rated in color temperature - degrees Kelvin (K). Low numbers indicate redder light while high numbers indicate bluer light; red light is designated warm and blue light is designated cool.
2100K - HPS
3000K - warm white
4200K - cool white, MH
5000K - "full spectrum"
6500K - "sunlight" or "daylight"
>9000K - specialty MH and fluoros

Fluorescents
Fluoros come in 2 types, standard tubes and compact fluorescents (CF or CFL). Tube fixtures house the ballasts that power the bulbs while CFL's can be screwed into any household socket. Conventional CFL's, that is. CFL's designed specifically for horticultural use often require a MOGUL socket. In both cases, the ballast is housed in the base of the bulb so they generate a bit more heat than tubes. The plants can't be quite as close. The biggest drawback with fluorescents is they only penetrate about 6". Blacklights produce uvA & uvB light and are useful as supplementals only. A better choice would be a 10,000K aquarium light. Fluoros designed specifically for horticultural use are available. Some employ targeted spectrum phosphors emitting a purple glow.

High Intensity Discharge (HID)
There are 3 varieties of HID lights useful for growing, HPS, MH, and MPS. HID lights require a ballast to provide the power to ignite them. Some have the ballast built into the fixture and others are available with a remote ballast. I recommend the remote ballast types for two reasons. First, the ballast is heavy and incorporating it into the fixture creates a very heavy fixture to hang over your delicate plants. Second, ballasts produce heat and being able to locate a remote ballast outside the growspace helps control heat. Electronic ballasts produce much less heat but are relatively expensive now. Horticultural lighting systems are available with shrouded cords. You simply hang the light and plug it in.

As the name implies, HID lights have a higher intensity and penetrate farther than fluoros.
50-70W penetrates about 1ft
150-250W penetrates about 1.5ft
400-600W penetrates about 3ft
1000W penetrates about 4ft

High Pressure Sodium (HPS)
HPS can be identified by the rosey glow it emits. Watt for watt, it produces more overall light than MH. HPS induces stretch (longer internode intervals) due to its redder light. It emits a spectrum useful for growing throughout the lifecycle although many growers use them only for flowering. Plain HPS bulbs work just fine, providing ample useable light for growth, but there are bulbs available with an enhanced blue spectrum to aid foliage growth and combat stretching. EYE Hortilux, Sunmaster, and Phillips Son Agro are 3 well known brands. Currently their cost is about 5 times that of a regular HPS bulb and worth it.

Metal Halide
MH emits a more natural white light. Watt for watt they emit less light than HPS (36,000 lumens for a 400W MH vs 50,000 lumens for a 400W HPS). Plants grow very compactly under the bluer light of MH, therefore many growers use them for vegetative growing and switch to HPS for flowering. Plants do very well under MH throughout their lifecycle, but the lack of red light inhibits flower/fruit production so the plants yield somewhat less. Sunmaster and others now make MH in enhanced spectrums as well; cool MH (4000-6000K) for vegging and warm MH (2000-3000K) for flowering. Light systems designed for aquariums are available with MH in the 9000K range. MH also produces a *small* amount of uvB light which is theorized to increase resin production and therefore increase potency.

LED
There are several websites to visit. LED Grow Lights.com offers proof that they work and excellent information on growing applications, with specific information on plants with low light requirements and those with high light requirements.

How much light do I need?
Cannabis is categorized as a high light plant. There are minimum levels of illumination required to insure compact plants. I have read that gardens can be successfully lit by as little as 2500 lumens/ft² when vegging and 5000 lumens/ft² when flowering. I have never used anything less than 3000 lumens/ft² for vegetative plants and 7500 lumens/ft² for flowering plants (in HID terms: 35W/ft² for veg and 60W/ft² to flower). Intensity degrades exponentially as you get farther from the source so the lights have to be kept close to the plants. To the indoor gardener that means less penetration through dense foliage. Ventilation is the key to keeping the light close. Air-cooled, tempered glass shielded hoods go a long way toward controlling heat. A small fan blowing right at the bulb works well also.

Broadside Lighting
The angle of light is important as well. Rays of sunlight are almost parallel by the time they reach earth due to the distance between earth and sun. A 10ft plant is illuminated equally from top to bottom outdoors. That is not the case indoors where the plants are a few feet at most from the light. Hanging lights vertically without reflectors at varying heights between rows of plants insures illumination to the bottom of the plants, penetration to the center, and dense growth along their entire height.

[cocogrower]

or you can have tried to summarize the post for the readers of the forum, but you probably dont understand lighting quite like the person who wrote the initial article did, so i will help break it down to the people who might actually read this topic.

metal halide lights should be used for vegatative purposes, because it more closely simulates the light the plant would be given by the sun during that phase of life. compact flourescent lights, or cfl as they are more commonly called, can be used for veg purposes, but primarily for freshy rooting clones, or pre-sex seedlings. once the plants become 6-8 internodes high, the cfl is not intense enough to properly grow the plant.

high pressure sodium as a more red tone to it, which is designed to replicate the warm color of the sun during fall months. because of this, it is the only light that should be used for flowering, since the plant has developed, and adapted to that particular light color for optimal flower growth.

as for depth concerning lights. lumen output is the most important factor to an indoor, artificial light grower. lumen count will determine exactly how well your plants produce. there are two things to keep in mind, a) the footprint of the growing area you want to grow in will determine watts, b) the number of plants you would like to grow in that area.

a 400/430 watt hid light can light up a 2x2 or 2x3 footprint with the proper reflector.
a 600 watt hid can support a 3x3 footprint, while a 1000 watt hid can light up a 4x4 area.

now you have to consider how many plants you'd like to grow within that footprint. the more plants, the less space between them, meaning the shorter they have to be. fewer plants result in bigger plants, requiring more light penetration.

example:
a friend grew strawberry cough, the original variety from the east coast, under 1000 watt hps lamps. he grew fewer plants, taller, for more "robust" yields. he did fairly decent, gettin 8lbs from a 4x8 footprint, though even he admitted, about 20% of the weight was wispy, and just lack luster, not worth selling. even with that said, he got 4 ounces per square foot.
i took the same stock, procuring a clone from him. i instead grew under 600 watt hps lamps, sitting over a 3x3 footprint. i dont like tall plants, i prefer my plants to be under 28", so in one 3x3 area i simply fim'd 9 plants, allowed them to bush out, then cut back all flower sites to give the most within a 1" zone across the top of the plant. the other 3x3 got a sea of green, that was fim'd, and then forced to flower. the 9 finished plants netted a total of 35 ounces, or a little over 2lbs. the sog on the other hand, netted me 4 lbs. when the sea of green (sog) plants finished, they were only 18" tall. they were planted in 4" cubes, and piled into a 3x3 table. each 4" cube was giving me 20-24 grams. the first nine/3x3 footprint developed about 4 ounces per square foot, while the sog gave me 7 ounces per square foot.


posting articles for people doesnt do much but eliminate some research.

[rebel dawg]

No need to be condensending my friend. If you have a better way of explaining lighting feel free to have at it but don't cut me down for utilizing the tools at hand and not recreating the wheel.

[Helping Hands]

WATTAGE, Ultraledlights

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Google: What is watts in lighting? The top one "Lighting" will tell you watts is the amount of work done. (unless you are a half watt, or is it wit?) Watts is how the electric measures your electric usage by the amount of work it has done. Lumens is how you measure brightness not watts !!!

As far as plants, wavelengths is what is need for growth and flowering.
NOT HOW BRIGHT IT IS TO HUMAN EYES.

If you are growing plants indoors, then the color of the light that your grow light emits is quite vital to your plant's health. Young plants at the seeding stage require blue light in order to grow properly. Mature plants, such as a flowering or fruiting plants, require red, yellow and orange light in order to get the plant to produce the flowering and fruit that you want.
All of this is dependent on the light that you use with your plants. LED Lamps come in a wide variety of colors, so it is easy to get the exact grow lamps you need in order to get the results you want from your indoor plants.

I hope this has helped in understanding LED's.

Very nice guide Rebel Dawg.

[astra007]

make all the links work or i'll start deleting

[Helping Hands]

I have been working with white led's and so far they seem to be doing very well. White is the full spectrum of light waves, this may not be as strong as the red and blue but it does seem to be doing as well as the red and blue so far. Ultraledlights is the group I have been working with.

Ultraledlights will build a panel how you want it (custom) made. I have had sucess with so far with these lights.

[makeitlegal420]

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[Widow Maker]

Ultra-violet light is very important to THC production. Suppliment HPS with a source of UV during flowering/throughout growth.

[KaliKitsune]

I would like to say that LED lighting has poor canopy penetration. I tried using an LED grow light kit by itself, compared with a standard T12 fluorescent shop light, and the fluorescent won. Yea, you're emitting a higher PERCENTAGE of PAR (photosynthetically active radiation) with LEDs, but it doesn't penetrate nearly as well as other light sources, since it's directed and not diffused. This is good for Scrog setups, but not very practical for any other method.

On a side note, getting a whole bunch of proper nanometer RED LEDs REALLY helps out with your budding at the canopy level.