LEDs DO work. please do not come into this thread and say they dont.

Peak absorption:
chlorophyll a-439nm(63%),667nm(43%)
chlorophyll b-469nm(80%),642nm(20%)
carotenoids---439nm(57%),483nm(60%)
phycoerythrin-590nm
phycocyanin---625nm
Overall-------425nm(99%),640nm(83%),665nm(90%)

absorption graphs:
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http://ncr101.montana.edu/Light1994C...%20Gei%201.jpg

Procyon (LED light SnS is using)has:
450nm-29%
635nm-71%
7:3 R:B

LED info:
lumen to watt conversion LED Wattage
Photopic function factors

LED suppliers:
LedEngin, Inc.
Mouser Electronics - Electronic Component Distributor
Enfis
Roithner Lasertechnik Vienna Austria ------x laser diode laserdiode optic collimator YAG laser semiconductor laser laser module lasermodul LED photodiode MID-IR InGaAs DPSSL UV-LED GaN white LED
BestHongKong.com ProLight 5 Watts LEDs
Rapid Electronics - Electronic Components > Optoelectronics > Power Leds
http://www.luxeonstar.com/http://www.luxeonstar.com/
EPITEX INCORPORATION

To convert the spectrum from Watts to uE/sec/nm use the appropriate physical relation and constants (uE/sec = power in Watts X wavelength in nm X 8.36 10-3). After you have your watts corrected for the wavelength (explained how to do a couple posts ago), just multiply by the wavelength and also by 8.36E-3.

Example:
For this example say we have a 200lm 660nm LED.
This LED gives 200lm of light, the value we want to convert.

1)Convert the lumen output to watt output.
goto LED Wattage. 1lm of 660nm light is .024W. (divide the lumens by the conversion factor to get watt output). So 200lm of 660nm light is 4.8W of light.
2) Now multiply the watt output (in this case 4.8W) and multiply by the wavelength and 8.36E-3. So 4.8W*660nm*8.36E-3=26.48 uE/s.

So this 660nm LED gives 26.48uE/s. If this was over a 1m^2 area, then the PAR is 26.48uE/s/m^2 (or uE*s^-1*m^-2). For comparison a Lucalox 400 hps is about 600uE/sec/m^2. So about 23 of these 660nm 200lm would give the same PAR (photosynthetic active radiation) as the hps.
Designing A Simple Lighting Layout - Venture Lighting - Lighting A Better World
http://www.kitchenculturekit.com/lighttable.PDF

5mm LEDs:
5mm LEDs have time and time again proven they can't handle flowering the plants. Here is a thread on that:
LED Grow: 1st grow, 56W max, Northern Lights


phycoerythrin & phycocyanin:
red n blue organic dies. in combination there most active from 590-595 and there job is to receive the wrong colored light and recycle it to the correct frequency. lighting them alone can provide the 660 straight to the chlorophyll. One also carries nitrogen, but that was in industry. having these receptors active will probably help facilitate in the conversion of all off frequency light from the description of there filtering techniques to achieve the 660

green light absorption:
The chlorophyll absorption spectrum does show that chlorophyll in a test tube absorbs only about 2 to 3% of the green light. However, that is very artificial because a leaf is highly . structured. Salisbury and Ross (1985) note that in the intact leaf, a green photon may not initially be absorbed by a particular chlorophyll molecule but it is reflected and then gets another chance to be absorbed, and perhaps another, and another, etc.
PHOTOSYNTHESIS

White LEDs:
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carotenoids:
http://www.iupac.org/publications/pa.../6301x0123.pdf
http://www.life.uiuc.edu/govindjee/papers/carotfig7.jpg
http://www2.mcdaniel.edu/Biology/botf99/photo/attcx.jpg

Pulsing LEDs:
Quote:
so instead of long slow electricity usage you get super spikes every 200ms? wouldnt that strain the hell out of your equip?

Exactly right SnS. You overdrive the LED's for a shorter period of time. The LED's are fine with this, as long as they are pulsed for the correct duration so they dont burn out (Most LED sompanies give pulse time and rate for overdriving LED's). The paper proves that with 100us pulses, photosynthesis remains 100% of that with constant light. Were not trying to trick the plants by "flickering" the lights, merely providing increased amount of light over a shorter amount of time by overdriving them for 100us pulses.

Quote:
but is turning on/off so many times going to hurt the leds?

LED's can turn on in 200ns. There is no harm done to the LED's by pulsing them, it actually increases life expectancy (if overdriven than life expectancy stays same).

Opie- Photosynthesis only happens so fast(but still very fast)...its not like the more light you give it the more it will grow(there is a linear relationship between amount of light provided and plant growth, up to a point). Plants require certain amount of photons per unit time to attain cellular reactions for light cycle, sugar creation, ect.

this is from the paper:
Much of the light used for photosynthesis by leaves within canopies is from sunflecks (Pfitsch and Pearcy 1989; Pearcy 1990). These sunflecks range from milliseconds to minutes in duration and their photon flux densities can be as bright as full sunlight.

So plants undergo photosynthesis naturally with these "pulses" of light.
https://mywebspace.wisc.edu/tsharkey...ght%201995.pdf



Flower with shorter Nights

There are another pair of pigments involved in things here - phytochrome-R and Phytochrome-FR. Phyto-R is most sensitive at 660nm Red, while phyto-FR is most sensitive at about 730nm Far-Red, hence the R and FR naming (IE, JUST 735nm and very near wavelengths, but nothing under 710nm or so). With 735nm far-red/near-infrared emitters available then it's possible to flower cannabis with 15 hours 'daylight'. How? Why? Well, the plant senses that critical 12-hours-darkness that triggers flowering in cannabis because a critical amount of phytochrome-FR has slowly, naturally, reverted to phytochrome-R during the dark cycle. But during the 'day' 660nm red light converts the phyto-R into phyto-FR, while far-red 735nm light more slowly converts the phyto-FR back to phyto-R. So we run all lights for 15 hours, then run nothing but 735nm for another two hours and finally 7 hours darkness.- artificially driving much of the phyto-FR back to phyto-R without waiting 12 hours for the natural reversion- so you can actually flower with shorter nights.

That's 30% more light per day reaching the plant, the result is that we can pump 25%-30% more energy into the plant each day - that means 25%-30% more growth - during the flowering cycle. Pushing even longer is probably possible, with sufficient intensity of 735nm alone during some portion of the 'dark' cycle. Several experiments have already documented this effect.

I hope this was some what of a good recap