No more circles!!!
Hey all, hopefully this can clear up the questions on LED vs. HPS (specifically HID)!
Firstly, LED and HID lights are effective, but using them right since they differ in their output is essential to success.
LED's, for example, emit specific frequencies of light that are beneficial to the plant. However, the intensity of the light is extremely weak and fades quickly. For this reason, the LED has to be within a few inches of the plant to get enough light down to its lower branches during flowering which is ineffective considering the cost of LED's for the time being. On the other hand, there is very efficient power usage which is convenient for small grow ops of only a few small plants, and while the coverage is limited, it is not a complete waste of money since plants have been shown to grow well under quality LED lights that have broad spectrum ranges, known as tri-band or quad-band ~ (3 or 4 frequency type diodes installed into the LED to ensure that no spectrum of light which is vital to the plant is missed)
the LED light in the link is 5 band, and is a good source for information on LED products out there
http://www.prosourceworldwide.com/product_p/illuminator pro series 350w.htm
Now, while HID lights are power sucking monsters and every grower despises the heat (unless your a winter grower 12 months of the year), they are extremely effective for covering large areas of space with intense lighting. In addition, many lights (specifically hortilux), have worked tirelessly to perfect their formulas to produce correct lighting for plants. For those who don't know what seperates a good HID bulb from another, its the chemical make up of the gas inside the tube! When a company spends time researching how to perfect a light, they are combining different ratios of gaseous elements and seeing which ones produce the correct frequencies when a current of e- (electricity) runs through it. Thats why even though two HID bulbs may put out the same amount of lumens (light intensity), if its not the correct frequency it won't grow as well
!
From a personal perspective though, I would wait for LED lights to evolve, because in addition to the actual LED diodes becoming more powerful, people are only now starting to experiment with the correct frequencies for light so the LED kits will evolve rapidly over the coming months while HID lights have a solid track record, and are actually improving. If i was on an e- constraint though and had limited room, I would consider an LED and probably use the one listed in the link above.
Also, it looks as though plasma lights are evolving at a fast rate and I think that in a years time, most people would enjoy having 250,000 lumen output for only 700 Watt input
http://www.youtube.com/watch?v=atrKO1tnNBY
If you have any more questions don't hesitate to ask!