An interesting find related to our discussion here: "A key part of our research involved the determination of which light frequencies or wavelengths would produce superior plant growth results." http://www.patentstorm.us/patents/6921182/description.html Since LED's represent a relatively narrow band of light, as opposed to HID's or Fluoro's, the researcher's used these lights for accuracy purposes. Prior research that they found gave a broad suggested range within bands 620-680, or 700-760 nm (red) and 400-500 nm (blue). After a year and a half of research, they settled on three more specific light wavelengths that produced the best plant growth results. "660 nanometers (nm) is the wavelength that drives the engine of the photosynthetic process. The 680 nm wavelength is perhaps closer to the peak absorption wavelength of one of the two chlorophylls found in higher plants. However, at 680 nm you miss completely the absorption curve of the second chlorophyll, and furthermore the output curve of a 680 nm LED has a fair amount of light output above 700 nm, which is known to cause unwanted morphological changes to plants. LEDs of 680 nm output are also rare in the marketplace, making them relatively expensive. Our choice of a 660 nm first wavelength component is a compromise wavelength commonly used in plant growing research, which supplies energy to both types of chlorophyll without emitting enough light above 700 nm to adversely affect plant growth. The 620 nm LEDs used in the aforesaid Ignatius et al. patents, are meant to provide the light energy for photosynthesis, but a look at the absorption spectrum for the two chlorophylls shows that this wavelength falls almost entirely outside the absorption curve for chlorophyll. Our research showed better results using LEDs of 660 nm and 612 nm rather than the wavelengths of 620 nm and 680 nm. Beneficially, LEDs of 660 nm are also readily available in the market, and are very inexpensive. Our second 612 nm wavelength component was selected not to promote photosynthesis, but to match one of the peaks of the carotenoids. As noted in "Influence of UV-B irradiation on the carotenoid content of Vitis vinifera tissues," C. C. Steel and M. Keller (http://bst.portlandpress.com/bst/028/0883/bst028883.htm), "carotenoid synthesis . . . is dependent upon the wavelength of visible light, and is diminished under yellow and red filters." By providing the orange 612 nm light, we not only promote creation of carotenoids, which are required for plant health, but also add a little to photosynthesis, since the carotenoids pass their absorbed energy to chlorophyll. Carotenoids are required for plant health due to their ability to absorb destructive free radicals, both from solar damage and from chlorophyll production, whose precursors will damage plant tissue in the absence of the carotenoids. During research we found that, beneficially, test plants turned a deeper green, i.e. produced more chlorophyll, with the addition of our 612 nm light component. This ability to increase a plant's chlorophyll content with this specific light wavelength is an important aspect of our invention. Blue light of about 465 nm, this wavelength being non-critical, is strongly absorbed by most of the plant pigments, but is preferably included as the third component in our lamp to support proper photomorphogenesis, or plant development. Any LED near this wavelength will work as well, but the 470 nm LEDs are commonly available and less expensive than many other blue LEDs. Regarding the proper proportion for each wavelength, it is known, from independent laboratory research, that a blue/red proportion of 6-8% blue to red is optimal. In sunlight the blue/red light proportion is about 30%, but this is not required by plants. More than 8% blue light provides no additional benefit, but adds to the cost of the device since blue LEDs are among the most expensive to manufacture. In our device we include about 8% blue light, which is near optimal for plant development while offering the greatest cost savings. Our research showed that best results were obtained when the output of the 612 nm orange LEDs in our device was added to the output of the 660 nm red LEDs when calculating our most desired blue/red proportion."

Thanks for the input, but I'm not so sure that you really did cut to the heart of the matter. Surely the number one biggest factor that growers will care about is the amount of light that they get. Documents such as the one I linked to claim that T5s are more cost-effective for the same amount of light than metal halides and I have my doubts. There are other issues like light distribution and spectrum but I think they can be dealt with if necessary using either light type. There is a segment of the buying public who are interested in growlights which emit the smallest heat signature in order to avoid detection. This has been one thing which has driven sales for the T5 lights. If that is what is driving T5 sales then growers are being thoroughly scammed by the marketing people. 100,000 lumens of T5 fluorescents give off just as much heat as a 100,000 lumen HID lamp, probably even a little more. Please see Myth #1 of Ten myths of growing under lights. Is a very hot point source more of a risk for illegal growers than the same heat distributed more widely? The amount of light you can put on the plants will depend to a much greater extent on the distance that the leaves are from the plant than the fixture. The kind of light you want depends on the kind of plants you have. OK, you confused me. I think I know what you're trying to say, but I don't want to put words in your mouth because there are some more myths here, related to penetration. Also, I'm not sure how valid the comparison of four 54W T5's to a 1000W HID lamp is. The light output is in no way comparable so there doesn't seem any point comparing the prices. Try 20 T5s to get about the same light as a modern metal halid bulb. Personally I wouldn't pay even half the prices you have quoted for HID bulbs, although I appreciate that you can pay that much if you really want. Similarly, 54W T5 bulbs are available for much less than $17, about $8 if you are prepared to buy them by the case, which you'll have to if you want that much light :)

You are quoting random rubbish from the internet again without checking what is happening today in the real world. I doubt you can find a CFL in Home Depot or any other store in any state of the union, and probably not in an internet store either, which produces anything more than a lumen or two away from 65 lumens/watt. There are however, a number of compact fluorescent designs which considerably exceed this efficiency, mostly high power devices with relatively few bends. You continually compare your infamous CMH bulbs with obsolete technology, presumably for greater impact on your sales targets, but it is highly deceptive. Please compare best practice CMH technology with best practice technology of other bulb types. The PAR CMH does indeed produce a highly focussed beam just like the halogen reflectors it is designed to replace, but this property is of only limited value for growing plants. In fact most growers strongly prefer a more diffused light to allow maximum intensity without localised scorching. Some form of reflector, baffle, or enclosure is important to getting maximum light from any bulb onto the plants. Some CFLs come with an integrated reflector, some don't, but something should always be used for plants. A simple device like a white card baffle surrounding the area is extremely effective. And what is this about horizontally oriented. It is oriented whichever way you plug it into a socket. It is in fact vertically oriented with respect to the reflector, a choice which is equally as effective as any other orientation when combined with an appropriate reflector shape. In this case, the vertical orientation with a round reflector gives a symmetrical beam spot, highly desirable for this type of bulb.

OK. I am going to try to post a picture directly into this post. The picture is of how I plant my seeds. I fill a clear plastic shoebox sized container with about two and a half inches of seed starting mixture and level it out. Then I use the eraser end of a pencil to punch in 8 to 15 equally spaced holes about 3/8 of an inch deep into the soil. Then I put an equal number of seeds into a small dish of water and wait until they get wet enough to sink. Then I put one seed into each hole. The wet seed will stick to the pointed end of the same pencil for dropping them into the small holes. Then I cover the seed with a thin layer of pure vermiculite, put the cover on the container, put it on a heat mat or into my oven where the pilot light keeps it at around 85 degrees, and wait, usually four to eight days. As soon as the first seed sprouts I remove the cover and immediately put the container, sprouted and unsprouted seeds alike, under my lights or outside on the patio in direct sunlight if it is over 50 degrees outside.