Ok, I would use one bulbfor every two cages, so you get even lighting. I would look at the readings for that particular brand of light(there are studies online at various distances).
At about 2 feet, most MV bulbs will output(I might be wrong, so check the the actual ouput/readings) ~20 micro watts per cm. sq. (mw for this post).
I think that is a good compromise between intensity and coverage. At 3 feet plus, they tend to drop off, unless you use a spot, which are only good for small areas in big enclosures(not those cages).
At 2 feet above, you get good coverage on one side of each cage(factoid: Some MV bulbs have been found to produce MORE UVB radiation at the 45 degree mark than from the center!!!)
This leaves adquate area for the chameleon to stay high up, but not in direct UVB radiation, if they want.
Your cages seem fairly tall, so raditaion/thermoregulation should not be a problem, as long as the MV bulb is NOT placed directly on the top of a SINGLE cage. If that is doen, they wont be able to escape it unless they go down.
Now that you have it set up that they are recieving 20-30 mw of UVB in their cages, determine how LONG you want to expose them to it. I suggest you look at that paper by Dr. Ferguson, and see how much radiation the pardalis were exposed to that had only .5-1 hour of radiation. They had about 40-5 mw for .5-1 hr. SO, you could extrapolate that to get similar results from the aforementioned setup, you'd have to keep the lights on 1-2 hours instead.
Another thing to ponder, the MV bulbs put out much more uvA thant the sun lamps used in the ferguson paper. UVA is supposed to aid in their thermoregulation and behavior. Sunlight has thousands of mw of UVA, and hundreds of mw of UVB. Artificial lighting should attempt to follow suite.
I noticed that UVA was NOT a factor in Dr. Fergusons study, nor was it controlled. For this study to be really helpful, the amount of UVA would remain constant, and the UVB would change--or the proportions of UVA and UVB should remain constant.
However, he was using available UVB lamps, so there is nothing to say except that it is a potential source of error.
I would think that a bulb suspended one or two feet from the tops of two cages, turned one for one or two hours a day, would provide adequate UVB and UVA for the chameleon. I would keep the cage lighted with florescent bulbs, outputting UVA, and an incandescent heat source--MV bulbs do NOT put out as much heat as an incandescent bulb, and at times, the chameleon will want heat,but not UV, so you still need one regardless of what the MV makers say. Just keep the MV on for a few hours a day, and you save money too.
My own personal experience with MV bulbs is very short, but very fruitful. I put one above my big male veild, who has excellent coloration, but was staying UGLY in the day(brown and maroon).
As SOON as I turned the MV bulb on, he immediatly basked--different;y than he had done before. HE turned bright, and stayed bright, until I took it away for my MBD female veilds.
They were raised in the sun, and were growing REALLY fast, much faster than the ones I raised. I intentionally avoid over feeding my babies, so they have a more natural growth rate. They were apparantly already growing incredibly fast, so when I started feeding them "normally"
to my standards), they did not immediatly slow down, they KEPT growing for a while, but they were not able to keep up, and developed MBD--despite their reptisun, and despite their repcal every other feeding. So, I put the MV bulb in between the cages, about 2 feet away. I gave them rep-cal twice every week--just in case, they were like jelly for god's sake. Then I cut back after they "hardened up". NOw, they rarely get Repcal, but are back on track, and doing great.
I am ready to give them their reptisun back, and give that male his MV bulbs---he's looking ugly as heck, and it ticks me off to see him like that.
I know peole that have had MBD develop from babies when reptisuns were used. I do not know of anyone that has had the same thing happen with MV bulbs--even the cheap $20 ones you can find online, that produce half of what powersuns do.
E
