(I was not sure which forum to place this thread in, so please feel free to move it)
Understanding UV bulbs and what it all means..
I am writing the following thread in the hopes that it may possibly help anyone who is having issues with lighting for their animals in need of proper UV levels. (Iguanas, bearded dragons etc).
Rusty Reptiles has gone through many bulbs and I have come to the liking of the following two.
The first is the Repti Sun 5.0
Can be seen here:
http://reptiledirect.com/index.asp?P...PROD&ProdID=39
The following description was taken from the link above.

The Results Are In!!! Recent tests at the Boston University School of Medicine show that Zoo Med's Reptisun 5.0 UVB and Iguana Light 5.0 UVB bulbs induce 7-DHC conversion to Previtamin D3 at a rate 23 times greater than the next leading UVB reptile bulb! Vitamin D is formed in a two-step process. The first is an isomerization of 7-dehydrocholesterol (7-DHC) to previtamin D3 (preD3) which is catalyzed by ultraviolet B (UVB) radiation. Ampouled samples of 7-DHC in hexane solution were exposed to radiation produced by the test lamps at six inches for 15 minutes on ice. The samples were then analyzed by high performance liquid chromatography to determine the percent of 7-DHC converted to preD3. Of the [six] sample bulbs tested, the Zoo Med Laboratories (San Luis Obispo, California) Reptisun 5.0 and Iguana Light 5.0 demonstrated a strong capacity to induce 7-DHC conversion to preD3... . Figure 1 diagrammatically represents the results of these analyses. -David M. Jackson, Ph.D. Figure 1 & Table 1 (left) Conversion of 7-DHC to preD3 induced by different light sources.

We use these bulbs for our turtles, and tortoises. Also our bearded dragons, and any iguanas that are caged.
The second bulb that we use is only used in room sized enclosures. These are a spot light that give off a good amount of Uv. These bulbs are used for our free roaming iguanas.
These are the Power Sun Bulbs:
http://reptiledirect.com/index.asp?P...PROD&ProdID=37
Here is a description of the bulbs:

The Power Sun UV™ is a self-ballasted mercury vapor bulb with two main components. The first is a standard incandescent filament, which is the first to light. The second is a mercury vapor arc tube, which takes a few minutes to heat up. There will be a noticeable change in hue (or color) when the bulb is completely warm and fully functioning. Because the Power Sun UV is a self-ballasted bulb it can be used in any ceramic socket that is rated to handle the wattage.
The Power Sun UV has nickel-plated threads to ensure that it will not corrode in humid reptile habitats. This new bulb also incorporates a short neck design, unique among mercury vapor lamps, that allows it to better fit into "clamp lamp" type fixtures.
Power Sun UV projects useable UVB radiation a far greater distance (up to 6 feet) than conventional fluorescent tubes. This makes it ideal for large enclosures and reptiles with high UV demands. Power Sun UV has all of the benefits of our award winning ReptiSun bulbs with the added benefit of increased intensity (50?W/cm2 UVB!!) and heat. UVB radiation has always been the safest, most effective way to ensure proper levels of vitamin D3 in captive reptiles and the Power Sun UV will continue to emit significant levels of UVB for all of its 10,000-hour average life (over 2 years with normal use.)

With the power sun bulbs, we only use the 160watt bulbs. They were tested and rated best for the output of UV.
The power suns are very large and get very hot. I wouldn’t recommend using one on an enclosure. They are meant for large room sized enclosures.
Andy Highfield wrote the following article. He is a highly respected by many in the herp community, and is in my book, the who’s who for tortoise and turtle keeping.
Please read the following to better understand UV and what it all means:
http://www.tortoisetrust.org/articles/lighting.html
I hope this may help
Thanks
Rusty