i think there is little shading at all with my setup....
Sorry HOHO, that sounded harsher than it should have done - I was just trying to think up the best possible way the light could be distributed. It obviously depends a lot on your plants and setup and I would agree that having plants like yours, a 45 degree bulb on a mover would create excellent light distribution.
1 square meter = 10.7639104 ft^2
10 000 cm^2 per m^2, so 1 square foot = 10,000 / 10.7639 = 929 cm^2
Topfuel says;
"so we need .23211 watts per Sqr. ft. of UVB"
.23211 W = 232,110 uW / ft^2
Since there are about 929 cm^2 in each ft ^2, that's...
249 uW / ft^2
I checked the number afterwards with
http://www.reptilesdownunder.com/reptile/reptilesAsPets/enclosure/uv/uvSA ;
"Outside on a sunny day, UVB readings are around
250 µW/cm2."
Comparing it with the document you've posted, it would seem to suggest the big bulbs are the way to go for some.
At first I thought they'd be way too much - but looking at the rate the UVB intensity falls off you can see how they'd be good if your high power bulb is a foot or two away.
You see that the intensity is roughly halving for every extra foot?
UVB wattages you see for the fluoro's are assuming you're going to have them close to your reptiles - the output of the bulb is actually measured right up against the glass.
Now apply the document you found, intensity halving every foot away, to CFL / fluoro.
What I found was these two sites;
http://www.reptilesdownunder.com/reptile/reptilesAsPets/enclosure/uv/uvSA
http://www.uvguide.co.uk/phototherapyphosphor-tests.htm
To put the numbers into context, even with something like a 26w 10.0 CFL, you're only meeting the sunlight requirement around 6" from the bulb.
With other bulbs, moving to a foot away produces something around 150 uW / cm^2 or less.
So two important things to note are that unless the CFL / fluoros are close the amount of UVB won't be the same as bright sunlight.
And, the intensity falls off so quickly that a foot further down the plant it'll be a lot less than sunlight UVB levels. HOHO's plants (with all the buds near the canopy) would help solve that, but for people with buds all over the place at different heights, illuminating from above with a UVB will mean you not only risk shadows but also having a low UVB level further down due to the light spreading out.
The other risk is, if you buy one huge wattage mercury UVB lamp, that might get the sunlight level UVB lower down but the intensity will be huge at the canopy and might stress the cola.
The short of it seems to be, if you buy CFL / Fluors you'll want 10.0 20W+ versions and they'll need to be around a foot or less from bud / tric heavy sites.
The big mercury bulbs produce lots more, but they also don't spread it very well using those reptile designs - they'll produce a cone of bright UVB. We could do with a standard mercury UVB that looks like a HID, to spread it out more.
From the link earlier in the thread, there's a picture of light distribution from the big mercury reptile lamps and you can see it's much stronger in a kind of V shape directly under the bulb.
Maybe we could modify the reptile bulbs by putting a cone shaped reflector under the bulb to spread the light out into a fan or smoother profile? Photographers and camera drews do the same when they light things with bright lamps. There's a reflector directly in front of the bulb to spread out the bright patch the glowing bulb makes - so you don't get sharp reflections in the images.
You can also buy UV mercury bulbs that look like this (and these may give a better spread);
It'll depend a lot on your situation. If you have insanely well trained plants and a light mover like HOHO, you could go for one or two higher power lamps and sweep them over the sites.
Say HOHO has his HID 2 foot from the canopy, from the document mindphuk linked to, something like the MegaRay 60w EB would produce almost exactly sunlight UVB levels at the canopy. His light mover is critical to keeping the light distributed through and the more uniform budding height means they'll all be getting about the same UVB.
http://www.megaray.co.uk/index.php?page=60w Zoo EB
If the UVB's were run closer, a foot or less, CFLs / Fluoros might work and would probably give a nice spread (the fluoros definitly would).
In the document mindphuk posted they list the age of the bulbs. Some of them drop off in intensity by almost 75% over a year. Others are a lot less.