found this.
I've been reading so much about lights recently that I decided to put some of the info I've found in one place. I'll just look at each type of light and some pros and cons and applications of each. I also want to mention problems with guidelines like watts-per-plant or grams-per-watt. Each type of light has a different efficiency and therefor puts out a different amount of light per watt. We shouldn't even really be comparing lights with lumens. Lumen is defined as a measure of the power of light perceived by the human eye.
Plants do not care about how bright the light is to a human eye. The links directly below discuss the wavelengths of light that plants use. This makes it a little difficult to compare lights that emit a huge variety of wavelengths versus only specific wavelengths (like LEDs). Take this into consideration in your lighting ventures.
Incandescent
Incandescent bulbs are going to be outlawed by 2014. They are very inefficient. That means that a lot of the power they use is converted to heat instead of light. These are never used for grow lights so we'll move on.
LEDs
LEDs are quickly becoming a viable option. LED grow lights come in panels because each single LED usually puts out less than 3W right now (3W being the brightest and most expensive). Low wattage LED panels found on ebay should be used for nothing more than light supplements and clones. LED panels usually have at least two types of LED on board. Each LED only puts out one specific wavelength but plants need a variety of wavelengths to grow. The link on photosynthesis above goes into detail on this subject. If you are planning to use LEDs then make sure you have blue lights for veg and red/orange for flower.
High power LED panels are very expensive right now. A 1000W HPS bulb is about $30 but the equivalent LED panel is about $2,000
. On the plus side, LEDs are the most efficient forms of lighting. Currently, the brightest LEDs output about 150 lumens/watt. That's about the same efficiency as high powered HPS lamps (>600W). LEDs are making progress every day so it probably won't be too long before we're all using LEDs, but right now they're a bit pricey.
Compact Fluorescent (CFL)
CFL lights are very common for small grows. They are pretty efficient (but not as good as MH and HPS) and are pretty small. They don't put out a lot of heat so they are good for small closet grows. CFLs are available in a wide range of color temperatures so they can be used for vegging (~6000K) and flowering (~2700K). These bulbs fit in normal household fixtures (no ballast needed). This makes it easy to make your own lighting fixtures with power strips and socket adapters to be able to plug the light into a two-prong outlet. To maximize light delivered to the plants the bulbs must be very close to the plants. Not touching, but they should be within a few inches of eachother. This type of lighting is good for smaller plants. Those of you wanting to grow trees should look into HID lighting.
T5
T5 fluorescent bulbs are a little hard to compare to other lighting due to problems in ratings which is discussed
here. Like CFLs, these have less heat output than MH and HPS so they can be placed closer to the plants and used in more confined spaces. They are available in larger sized fixtures (hundreds of watts) that usually come with a reflector and ballast built in. Again, these are better for smaller plants instead of giant plants. Here is a wiki on T5s if you're interested:
T5 on Wikipedia
HID Lighting
The following lights are categorized as HID lighting. These lights are about 8 times as efficient as incandescent bulbs and twice as efficient as CFLs and other fluorescents. These lights are usually too powerful for clones. Lower output lights should be used because if the plants are photosynthesizing too much before they have a root structure then they will dehydrate themselves.
Metal Halide (MH)
With MH lights we're getting into bigger grows. Power ranges from about 75W to over 1000W. The light spectrum here tends to be a little cooler than HPS bulbs so MH bulbs are better suited to growing in the veg stage. These lights need ballasts to operate. These lights tend to have a lower lumen/watt output than HPS bulbs but have a wider light spectrum.
Ceramic Metal Halide (CMH)
Along with LEDs, these are some of the newest lights on the market. These lights have about the same lumens/watt as regular MH bulbs but have a much wider light spectrum. I expect that these will become very popular since it appears that one bulb can be used all through veg and flower. These bulbs work with analog HPS ballasts but not digital ones. Digital ballasts for these lights will come along soon and will be able to operate these lights more efficiently.
High Pressure Sodium (HPS)
HPS bulbs have even more light output density than MH bulbs but tend to be on the warmer end of the light spectrum lending them to be great for flowering. These lights can be incredibly bright (~145,000 lumens from 1000W). These lights also need ballasts and produce a lot of heat so for higher wattage models, ventilation for the bulbs is necessary so as to not turn your grow room into an oven.
Summary
So what does this all mean? Well... there are a lot of factors that come into play. Here are a few bullet points, though.
-CFLs and fluorescents for smaller grows and clones.
-LEDs are pretty expensive right now but should become cheaper over time.
-HID lighting for bigger grows, but they usually require a ballast.
-Blue light/daylight/about 5700k bulbs for veg.
-Red light/soft white/about 2700k for flower.
-Higher power = Higher Heat= More Light = Bigger Growth = More Yield
