It's funny how hard we try to tell people to reproduce the chameleons habitat as best as possible, and then in regards to lighting, tell the exact opposite. If Wild chameleons can regulate, then I figure my Captive bred specimens can do it as long as I provide dense foliage.
But yes, the rising and falling of UV intensity could be an issue, but the UV in the sun in an open area without shade is quite powerful, and I would think especially in the areas there these chameleons are coming from.
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It has been recommended that Panther chameleons should have around 35uW/cm² for 12 hours a day if I remember correctly. Though their habitats in the wild seem to vary from thick vegetation and thin sparse fields so its hard to say where this info was recorded.
Most florescent tubes are only giving this much UV within the first 6" from the bulb. Aluminum mesh blocks probably in the range of about 35% of the UVB, depending exactly on what mesh you use. Meaning that many of the florescent tube bulbs are actually only effective in producing the amount of UVB recommended for Panther chameleons, in the first 4" below the bulb and only in the first 2-3" if you are using a Reptarium/Flexarium cage. Also factor in that the bulb is usually raised about 3" or MORE off the netting the in the larger lamps.
Correct me if I am wrong.
Now lets look at the same thing with a 60watt Mega-Ray EB lamp. The first 6" or so below the very center of this bulb are higher than found in nature. minus 3" for the bulbs hight being held over the mesh in the lamp- and then also consider the reduction of the UV from the screen- but well factor that in later. So, unless the chameleon is hanging ON the mesh upside down below the bulb, this unit is safe within the limits of nature as in full sun you would VERY rarely pass 500uW/cm² even at higher geographic altitudes. At a distance of 12 inches from the bulb, the lamp produces about 100uW/cm². If you are using a Reptarium, a chameleon sitting at 12" from the bulb, meaning (12-3) about 9" from the cage roof which is a respectable distance, would receive very close to the amount recommended for panther chameleons after you factor in the 50-60% diffusion. And there for not too intense if you construct the perches and branches correctly.
Keep in mind I haven't received my Solarmeter yet but this is just something that I was thinking (researched:
http://www.uvguide.co.uk) about when justifying to myself that MV bulbs are not too powerful for my panther chameleons.
This is one of the most important points in my mind, written on the site, and in some way it puts me at ease that they can somehow regulate the UV a bit better than I had previously given them beleif to.
All reptiles must be able to shelter from UVB light; a UVB gradient, similar to the heat gradient with which we are familiar, is necessary in the vivarium.