Information is always welcome, but I'm not entirely sure what conclusions to draw. That HID bulbs produce an intense light over a small area and an array of fluorescent tubes produce a less intense light more evenly over a wider area? I could have told you that :)

I think that it skates quickly over (perhaps misses entirely?) the key point that "penetration" (relative decrease in intensity from the top to the bottom of the lit area) is not a factor of the light source but of how strongly the light source is focussed onto a small area, and hence how slowly its intensity decreases with distance. In the good old days, fluorescents were so dim you had to have the plants touching the tube, and so never bothered to focus them well, while HID lamps were so bright you had to have them three feet away and so had to use a good reflector. Hence it appeared that only HID lamps had any penetration while the real story was that any bright lamp focussed from a distance would have the same penetration. Reflector/baffle design is of course key and the linked results apply to the typical small highly focussing reflector supplied on HID grow lamps.

Perhaps there is an ingrained mindset in the pothead community that is slowly being modified? I read some other related threads and there seems to be a slow shift away from the "HID is the only way" mindset that ruled a few years ago towards the idea that the choice between HID and fluorescent depends more on convenience, availability, and initial cost than on outright performance differences.

Very interesting posts in that forum.

Shrub did you download the spreadsheet ?
I did, not sure I what to make of it but very interesting.

>>Hence it appeared that only HID lamps had any penetration while the real story was that any bright lamp focussed from a distance would have the same penetrationYup, that's why I would prefer HID over fluros for tall plants.HID spectrum is terrible but they are getting better.

Why can't they make an "HID Fluo" light? I'm sure this is a stupid question but I can't figure out why not.
ie a 5 cm fluo tube delivering high output in the 400 - 1000 watts?
This would Kick @%^, imagine a full spectrum Gro-Lux at 1000 watts.
I'm convinced this would make a big diffrence in growth quality of plants.