GigZ-16's Light Guide

[GigZ-16]

Light Guide
by: GigZ-16

When it comes to growing Cannabis, not every light source will do. Choosing a proper light source is essential to obtaining a good harvest. Organic gardeners believe the best light source is the sun, but this isn't always an option for the indoor rural gardener. The major types of artificial lighting are Incandescent, Black lights, Fluorescent, High Pressure Sodium and Metal Halide.
Some things need to be taken into account when deciding on the light source, such as budget, light spectrum, intensity, wattage, electric bill, etc. The proper color spectrum for vegging is blue, as it promotes leafy compact plants. The proper color spectrum for flowering is red, as it promotes budding. The proper light intensity for Cannabis growth is 2000 to 3000 lumens/sq. ft. The proper wattage may vary with the size.

2 x 2 ft. area 100 watts
3 x 3 ft. area 250 watts
4 x 4 ft. area 400 watts
6 x 6 ft. area 600 watts

Light sources

Incandescent - These work by heating a Tungsten filament inside of a glass covering until it heats enough to produce light. They range from 1.5 volts to 300 volts. These bulbs are simply not acceptable for growing Cannabis. They cause an excessive build up of heat causing heat stress and tend to stimulate stem growth. This results in plants that stretch too tall and fall over. they produce 18 lumen's per watt.

Black lights - These lights produce long wave UV radiation and little visible light. They are not good for growing all the way through or for any stage of growth to be honest.

Fluorescents (and CFL's) - Fluorescent lighting is the cheapest and most convenient source of light for the indoor grower. Especially the money saving Compact Fluorescent Light bulbs which do not require any ballast. These are easy to obtain and with CFL's the mounting options are endless. Fluoro tubes range in size from 6 inches to 8 feet and require a ballast to run. Fluoro tubes come in cool white, neutral white or daylight. The color temps are 4100 , 3500 and 5000 to 6500, respectively. The lower the color temperature, the less red light that is admitted and the higher the color temperature, the less blue light is emitted.. Therefore, Cool white would be better for flowering growth, while daylight is better for vegetative growth. CFL's come in the same tpyes and the same rules apply. For more on CFL's try this guide. Fluoro tubes produce 2500 lumen's per meter. Fluorescents produce 39 lumen's per watt.

High Pressure Sodium - HPS Bulbs come in anywhere from 150 to 1000 watts. They produce 100-140 lumen's per watt.They work by using electricity to put Sodium in an excited state, thus producing visible light. These bulbs emit light from the red spectrum and are best for flowering. Alot of growers prefer to switch to HPS bulbs for 12/12. These need a ballast and produce a good amount of heat, meaning they should be placed 12 inches from your plants and 18 inches from seedlings. Some growers prefer using this bulb all the way through. Extreme care should be taken when growing with HPS and MH as to not let any drops of water touch the hot bulb. This may cause any High Pressure lights to explode. These bulbs usually have a life time of 20,000 hours.

Metal Halide - MH bulbs range in watts anywhere from 150 to 1000 watts and require a ballast. They produce up to 125 lumen's per watt. Metal halide bulbs produce light by passing an electric arc through a mixture of gases. This bulb produces an abundance of light in the blue spectrum, making it ideal for vegetative stage. Many growers prefer to use MH for veg and switch to HPS for 12/12. These lamps must be placed a distance above your plants as they also produce excessive amounts of heat. MH has a life time of 10,000 hours.


The Cost of Running a Lighting System - To figure out the cost for an hour for a light, take the lights combined wattage, and divide it by 1000 to get the kilowatts used. Multiply that number by the amount your electric company charges per kilowatt hour. HID lights will use the number of watts it emits per hour, ie; 600w system will use 600 watts per hour.
(light wattage output / 1000) x electricity cost per kilowatt hour = Operating Cost per Hour
Operating Cost per Hour x hours used per month = Operating cost per month

I hope I helped someone. As always if ou have anything to add, post it up and I'll add it. Good luck.