I have a further question related to the above. If one can get decent, tightly packed tiny plants, would it be reasonable to opt instead for some kind of compact floro. lighting? The way I figure, the plants will be fairly uniform clones, and relatively low to the bottom of the cab. This will also allow for an adjustable lighting set up to be kept fairly close to the top of the canopy without fear of burning the plants, which would maximalize the use of those lights.

Could this work out well? Or would the grower still be better off using HID's, especially an HPS for flowering, even with it's relatively more intense heat and the need to keep the light further away from the top of the canopy? Because while it's true HID's are "better" in terms of lumen out put, couldn't there be situations where that is offset by having to keep it some distance from the plants, and further by the expenditure on extra ventalization, air conditioning, etc.?

Further, if floros are a possibility (ideally I'm talking about an actual growing space no larger than 3' x 3', possibly smaller), is there a specific type of bulb that should be used? If a bulb with more red spectrum for flowering is obtained (I've read that such compact floro. bulbs do exist), could it still be used for rooting/vegging as well, or would it be really worth getting a different "blue" bulb (if one can reasonably afford it)?

Indeed, I'd be kind of interested in info on how lumen output is measured for the various bulbs on the market (HID or otherwise), what distance from the bulb it is measured from, etc. This info, combined with facts on just what cannabis plants need in terms of light for good growth (with the first priority being the potency and the tightness of the buds themselves, yield being still significant but secondary consideration), would give someone the ability to make an informed decision on just what type of bulb to use in this type of set up.