Wow, finally someone on the forums that has a grasp of the situation with LEDs.
After OG's fall i registered here. I posted some about lighting, but at that time this board becames very unconfortable, and i get very little feedback. So i went to other boards. Now things seems to go smoother here, and ive read good threads about LED on this board, so im here again. :rasta:

1. While HPS is more efficient the LEDS, how much of that disadvantage can LEDS make up by being closer? I have been building arrays that use no lenses, 140 to 160 degree view angle and trying to get them placed about an inch above the top of the plant. I think the closest you can get with HPS is about 6 inch for a 400 watter and 8 inch for a 600 watter. And that is with air cooled hoods and a light mover.
My personal thinking is 100 watts LED is equiv to about 60 HPS at this time.
Mant people had a bad understanding of the "square law" and its meaning. It refers to how fast irradiance drops with distance. But its due to a given amount of photons are dispersed on a exponentially increasing volume of space as distance increases. When you distribute small points of light along the grow, you deliver the light exactly where its needed, so you can keep irradiances at leaves surfaces very even, as you dont need the light of each LED cover a large volume.

But light from a top HID dont dissapear magically with distance :wtf: irradiance goes dropping from very high figures on top to very low on bottom and edges, but its not due to less photons avalaible, but to almost same photons diluting on a larger volume as distance increases.

Of course there is optical losses as the light must travel larger distances. Dust in air absorb some photons (more as dirtier the environment), aswell as light bouncing on walls let part of the light at them. And it obviously happen more as more far is the light source (and the reflector footprint match less the plants area).

So distance affect light efficacy by two ways: less total photons avalaible and suboptimal photons densities at leaves.

How much less photons are avalaible depends of a lot of factors: how well the reflector footprint matches the grow area, how much reflective are walls, how clean is the air, if there is a glass barrier between the bulb and plants, how much reflective is the light's hood...so its impossible to generalize those losses. It depends of each setup. A well designed LED setup almost eliminate these losses, and it allows to use less total photons than a HID to get same results.

How many less photons? Little difference if you compare with a vertical HID setup surrounded by plants. For top reflectorized HIDs, optical losses at reflector are 20-25% of the total amount of photons emited by the bulb. With a glass barrier (cooltubes and such), its a minimun of 35% of the light emited. These are the minimun less photons we may use on a LED setup to get similar yield. As i noted before, there are other optical losses, but it varies strongly between setups. For a well designed HID setup (reflective walls, ventilated and filtered (clean) area, reflector footprint mtaching the shape of grow area) they exist but are small, so we may ignore it for doing estimations.

On the other hand, what have a large enhancement of light productivity (yield/uE of photons) is keeping irrandiance at leaves on the optimun range. For a whole grow room, the only data i have about this is the 35% enhancement from the NASA study. We must calculate it for cannabis, but until we do it, we may use this figure (with a grain of salt ).

So, answering directly your question the fact of using the LEDs closer reduces slighty the light losses, although keep irradiances at optimal levels. We may suppose initially an enhancement of 35% on photons efficacy. It means we can get same yield using about 75% of the total photons emited by a top HID.

(Important math's note: we are talking of enhancement of photons efficacy, so we may apply it to the baseline of amount of photons. If we use 75% of photons with 35% enhanced efficacy it result of a total efficacy of 75%+(35% of 75%=0.35*0.75=26%)=101%. )

If the enhancement on cannabis is of 25%, we must use 80% of photons (to get same results than a top HID).

Having this reference in mind, we need know to know how many photons emit a HID avalaible to plants. It depend of the setup, so the amount of uE to be delivered by the LEDs in order to get same yield depends of with what setup you compare it. For example, a generic 600w HPS emits 1000uE (per second) (good ones as Grolux, Hortilux, Plantastar, Green Power or Sunmaster may reach up to 1100uE):

-Verticaly unreflectorized . Very little enhancement, especially if plants are kept short (usually with this type of setup), so we must use near same amount of photons delivered (1000uE).

-Top lighting with reflector. Optical losses at reflector are 20% (very good ones), 25% on average (dirty or low quality reflectors may have way higher losses). It mean about 750-800uE. If we suppose a 35% of enhancement for optimum irradiances, we need 550-600uE of leds.

-Sealed (glass barrier) top lighting. Average losses of 35% on clean setups. So just 650uE avalaible. We will need about 475-500uE to get similar yield.

Take in mind HID are less efficients at smaller wattages. So its easier (less watts of leds for each watt of HID) to get similar yields as smaller is the grow.

I have yet to see a documented LED grow of more then .3 gram/watt/month and the grower has so far been unable to repeat that performance
Yep, current perfomance LED commercial units are producing about 0.2 g/W per month. But this parameter is very important to decide when comercial units are cost effective, but of little usefulness on the actual stage of development. g/mol of photons is a way more meangliful and useful parameter, due LEDs are improving very fast, and for a given amount of uE you need now 100W of leds, but one year later only 60W. At it depends too of how hard (efficiently) you are running those leds. As i noted on my last post, it affect strongly to their efficiency (uE/W).

When we determine production in terms of g/mol of photons we can extrapolate that data to watts required of any LED with known emission, so we could estimate the amount of watts to install to get a given yield target.

I dont know how many times ive claimed that we may use LEDs with accurately known emission on our experiments so we could get universal conclusions that can be extrapolated. BTW, Ive been little sucesfull. So im running now a group buy of components of known emission with about 20 growers that are going to do logs with them, using differents styles of growing (soil, hydro, scrog, LST, sog...) so we can get conclusions fast of the amount of light required to grow cannabis and get similar yields than with HID, fluos, etc.

2. I am undecided on getting better efficiency by running about mid-range on current and allowing better area coverage with more LEDs. Or running them rascals as close to max ma as possible, spending more $$$ on cooling in order to get better penetration. Any thoughts?
Thats a very personal decision. You must find the best compromise between initial cost and efficiency: more leds at lower current means higher initial cost but lower efficiency.

On the actual LED's state of art, they just may be cost effective on very small grow spaces. So i suggest to build an experimental LED setup very small and use them at very good efficiency figures. The size of such grow determined for your budget.

I try to avoid as much as possible active cooling. Of course its doable, but a failure of fans may result on permanent damage or strongly reduced life of LEDs. I prefer to rely on passive cooling and LED distributed sparingly along the grow so power concentration is low (thus easy to cool down): lower cost on fans, less electric consuption, increased efficiency.

At least, i suggest to follow this way for side and IC modules. If you want max power on top, modules on top may be actively cooled. Indeed, PC's socket heat dissipators are one of the cheapest options as heatsinks, and they comes with fans. You can conect the fans or not, depending on the density of leds you install and current used. Those bulky heatsinks arnt a problem on top, butthey are on IC lighting. As on IC we need lower power densities, often passive cooling are a better choice.

You dont need any penetration ability if you use the LEDs between plants, so you always may place LEDs very close to plants and using wide emission angles.

Relying on light penetration is a limitation of HIDs, not an advantage. We are so used to work that way that we not realize how bad its it: produce uneven light distributions (reduced productivity), and light passing though leaves increase strongly its wavelenght, resulting of a strongly far red lighting on bottom plants that produces fuffly buds.

3. What is your thinking in light ratios? Mine has been approx 3 to 1 red/blue with a little white light for insurance. However, I really want to experiment with a heavier blue ratio. I am close to the point where I think I can use LEDS in a vegging set-up where it will be able to outperform both CFL and HPS.
Check the Inada curve. It shows the amount of photosynthesis promoted for 1W of light of each wavelenght (2nm bands) (isolated, each waveband at a time; study performed on sunlight grown plants):

(i was to post here the attachment, but i dont know how to do it; anyway, its on the bottom of the post, open it).

The curve 1 is the average response of 27 herb plants (curve 2 are for trees). Note how the minimun photosynthetic response is about 465nm, the emission range of blue leds! Still lower than of green light.

Blue light is added because plants need it, not because increased photosynthetic efficacy (at least, at no CO2 limited irradiances). Cannabis is a little demanding plants in term of light quality: it needs very little (if any at all) blue to be able to grow (opposite to most plants). But blue light has some "colateral" effect that advice to use it: first, the lack of blue light strongly increases internodal distance, so you need to add some blue if you want the compact plants we seek for indoor. But just 30-40uE per sq meter are enough for this, while we rarely use less the 500uE/sq meter of average radiances. So we need less than 10% photons of blue, often just about 6% of total radiance in order to keep plants short and compact. As blue photons carry way more energy than red ones (in direct correspondence to its wavelenght: a 450nm photon carry 650/450 more energy than a 650nm photon), if we talk about PAR watts instead of number of photons (uE), then that 6% correspond to about 10% of total PAR watts. This are minimum requeriments.

But blue photons have another collateral effect that may advice to use higher amounts of it, and its especially important on LED grows due the high percentage of red photons: blue photons promote the opening of stomatas, while red photons promote the opposite (maximum effect peaked at 450 and 660nm, respectivelly). It affects the transition point between the light limited part of the photosynthetic response curve to the CO2 limited part of the curve.

So the higher the irradiances used, the higher the percentage of blue you need to add. Thats why blue enhanced HPS bulbs (or MHs) tend to work better as higher the w/sq ft used, while it offer little enhancement of gardens using low light densities

So if you keep irradiances low to medium (up to 250-300 uE/m2), you wont need to add more blue. But we often use higher irradiances in order to get fat colas, and then the internal (leaves) concentration of CO2 becomes very important to get good photosynthetic efficacies. So in that situation, if you are growing with LEDs and you want to keep light's productivity high, you need either supplement with CO2 or add more blue light so plants are able to keep CO2 internal concentration higher.

On a side note, the ratio of Blue, Green and Red (simplified ranges for B:400-500nm, G:500-600nmn, R:600-700nm) must be refered to the amount of uE or PAR watts, not to the number of leds or watts installed, as leds of different colors and running currents have different efficiencies.

4. For some reason, LED in combo with CFL seems to produce the best results. Any thoughts?
Thats due commercial units using just blue and red have spectral lackings that results on reduced perfomance. By adding white light, the perfomance of all photons are improved.

Apart of it, people are using to little photons per sq ft because they are wrong about LEDs perfomance. They strongly overstate it so they end installing too little watts. By adding CFLs, they complete the spectrum and add some more photons.

(Will you expect a good yield using a 100w HPS on 1 sq meter? LEDs arnt different, if you dont give enough photons you cant expect good yields)