UPDATE: 4 August, 2012
I've taken some flak for using CFL's with a recommendation from Jon Parr
to use Ceramic Metal Halide (CMH) bulbs. If I continue to supplement light next Winter I will switch over to CMH.
This is what Jon had to say:
Jon Parr (LINK) - ."CMH are not necessarily the best, but they are my favorite. MH emit blue light for veg, HPS emit red light for flowering, and CMH emit full white beautiful spectrum, including UV. Photosynthesis uses a fairly narrow spectrum of the blue and the red, and non at all in the green, in fact reflecting it, which is why plants are green. The jury is still out on how exactly UV is used, but side by side comparisons show healthier plants when a little UV is added, IDK. I do know that HPS are cheaper, about $20 and on the shelf at Home D for a 400W, as opposed to $50 for a CMH 400W. Bob, and Kevin, you will be amazed how cool HID lights are compared to flouros. The bulb itself is hot, yes, but the total heat generated per watt is less, and a vertical CMH bulb needs no cooling at all, not even a fan, as the natural convection draws a cooling air current upwards past the bulb. I pay $.45 per KWH, so efficiency is paramount, meaning no reflectors or glass to suck lumens. I hang a vertical bare bulb, and situate my plants around it in zip-grow style towers. Ideally, I don't want a single photon striking anything but plant. Is the UV dangerous from a CMH? Yes, probably, just as dangerous as it is from the sun. I have never noticed any discomfort, but I am in the sun working every day anyway. I've read that sensitive people advise wearing sunglasses, long sleeves, or even sunscreen if working around bare bulbs for extended periods of time. I have them lighting up my whole shop, but they are in closed fixtures with a glass panel, which blocks the UV.
I get my CMH here, and ballasts, and sockets are available for about $15 at your local head shop. http://advancedtechlighting.com/cdmed18.htm For flat grows like Bob and Kevin have, you'll want to add a wing style reflector to bounce light back down to the plants. The linked site also show some pictures of failed bulbs, and how the arc tube remains contained. The Phillips brand they sell are rated for open fixtures, a big plus for bare bulbers like myself."
For an explanation of why CMH are the preferred grow bulb WATCH THIS. Basically it is because they have a complete spectrum, and last longer
worked out a custom auction for me!
15 - 14W 5000K 800 Lumen CFLs
15 - 18W 6500K 1170 Lumen CFLs
for $65.00 including shipping charges!
But the auction he has listed now says
30 CFL Bulbs Total 15-2700K 15-6500K so you may have to ask for what you want.
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All along I have spent the time to find the best values when I had to purchase anything for this project.
With lights I feel that I may still be on the learning curve, but here is what I've found.
T5 and CFL seem to be the best bargain when heat, energy, and initial cost are all considered.
The luminous efficacy of a typical CFL is 50–70 lumens per watt (lm/W).
A typical T5 HO (High Output) bulb produces 92.6 lumens per watt.
T5 systems come ready made and have a professional look.
CFLs can be slightly less expensive if you are willing to invest the time to build a light bar. Here is how I built mine. It's 16 standard E27 bases connected in parallel on a 1 x 6 board.
As an example two light bars each with 8 - 5000K 800 Lumen and 8 - 6500K 1170 Lumen CFL bulbs should produce about 31,500 Lumen when new, but about 25% loss will occur during the lifetime of the bulbs.
Below are some pictures of how I made it.
|I first laid out the pattern and drilled 1-3/8" holes|
|Then I cut out the opening for the electrical connections to the standard E27 light bases|
|This is the top where the wire get connected.|
|This is the result.|
CLICK HERE for a full explanation of Color Temperature.
Expect to pay more for the higher K value.
2700K tends toward the red end of the spectrum and is good for fruiting while 5000K and 6500K tend toward the blue end of the spectrum and are best for growth. I plan to mix a few 2700K in for good measure, but I will use mostly 5000K and 6500K. Alone you may think a 2700K looks bright and white, but next to a 6500K it will look dim.
The cost difference is significant. I was able to find 2700K at Costco for less than $2.00. If the package does not have information about the color spectrum or if it simply says "Full Spectrum" it is most likely a 2700K bulb.
The best price I found for 5000K and 6500K was $4.14 at Lowes. I looked at eBay, but it appeared that the big box stores have the best deals until firstname.lastname@example.org helped me out.
The cost of each white plastic E27 base was $1.34 at Lowes.
Total cost for a 16 light, 368 Watt, 25600 Lumen light bar was 21.50 for the bases, and $66.00 for the lights. Plus a 1x6 and some wire for a total cost of about $100.00. It took about an hour to assemble.
I found R48 - T5 HO Fluorescent Grow Lights for $145.00 on eBay.
Considering the small difference in price the T5 light may be your best option.
The value if you buy your bulbs at a Lowes is about 200 lumen per dollar for the CFL 6500K and about 160 Lumen per dollar for the T5, but I think the T5 looks better. If money is an issue or you require a lot of lights then the cost may be the deciding factor.
For more information about lighting reference these links
An excerpt from Marijuana growers handbook by ed rosenthal, newest edition sums up the math very well.
Lux is a type of measurement of visible light to the human eye, is an industry standard in Europe.
PAR is a measurement of Quanta of light in PAR range, used in Horticulture research, and the a measurement of "daily light integral" accumulated PAR light during an entire day, also used in Horticulture research.
There are other PAR measurements for Energy in PAR range, and total energy, that is used by engineers and researchers.
PAR is usually expressed in Moles, which measure the number of light photons (one mole = 6.02 x 1023 photons) and are frequently combined with units of area and time to give you moles per meter per day.
Light output or intensity is measured in several different units, including candelas, foot-candles, lumens, lux, and moles. Many of these units are based on each other, and some are more commonly used than others. They measure three basic things:
*the amount of visible light emitted (candelas, lumens)
*The amount of light that reaches a defined area (foot candles, lux)
*and the total number of light particles (moles)
envind added this comment in the forum discussion "Lux Versus Lumen & Par Versus Ppf" on the GreenPassion forum
Lumens measure the visible light or "luminous flux" emitted in a defined beam. a single candela light source that radiates equally in all directions produces exactly 4(pi) lumens (12.6); a 23 w compact fluorescent emits about 1600 lumens.
The lux is similar to the foot-candle in that it measures the visible light intensity (luminous flux) that reaches a particular area, defined as one lumen per square meter. so 100 lumens concentrated in an area of one square meter equals 100 lux. if that same 100 lumens is spread over a space 10 square meters, you have 10 lux.