Bulbs that produce UVB and UVA come in two varieties - fluorescent and mercury vapor. Fluorescent UVB/UVA bulbs have been the standard for quite some time, with the ZooMed Reptisun 5.0 having the highest output of UVB/UVA as determined in more than one scientific study. The two components of UV serve different purposes in regards to reptiles.
The UVB wavelengths are needed by some lizards in order to help them convert dietary calcium to a form usable by their bodies. The UVA wavelengths are no less important as they affect what the lizard sees visually and higher UVA wavelengths can help stimulate more natural behaviors, breeding, etc. Now, all that being said, every fluorescent bulb produces some amount of UV, although in bulbs not specifically engineered to produce UV, it is negligible.
So, the difference between fluorescent and mercury vapor other than physical design and wattage is that mercury vapor bulbs produce a much more intense light and subsequently more UVB and UVA. This is also why they are usually more expensive than fluorescents.
As to full spectrum, it is a term that has been used to apply to UVB/UVA producing bulbs but more accurately is applied to fluorescent or incandescent bulbs that are coated in such a way that they mimic the color spectrum of natural sunlight giving more true colors. Subsequently, full-spectrum bulbs contribute to more natural appearance and behavior than traditional incandescent bulbs which typically have a yellow to red cast. The traditional fluorescent [typical all-purpose cool white] has an unnatural greenish cast.
So, there you have it. By the way, you mention Power Sun which is the ZooMed brand of UV producing mercury vapor bulb. I'm not sure what your other bulbs are that you mention.
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Matt Campbell
Animal Keeper, Small Mammal/Reptile House
Lincoln Park Zoo Chicago, Illinois
Assistant Curator
Wildlife Discovery Center at Elawa Farm
Lake Forest, Illinois
