Lighting
Lighting is of central importance in chameleon husbandry.  Light is a source of UVA and UVB radiation, heat, and is necessary for proper plant growth.  Below we will look at UV light, heat lamps and full spectrum lights for plant growth. Please keep in mind that like everything else in this hobby, lighting is not something to consider in isolation from other factors such as supplementation, enclosure setup, temperature, etc.
UV Light
UV light plays a significant role in the lives of chameleons, including appetite, digestion, mating behaviour, vision, muscle function, and skeletal health.
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Ultraviolet light is a range of wavelengths of light from 180 nanometers - 400 nanometers. UV light in the 180-200nm range is called UVC, and is deadly to most living organisms. Luckily, our atmosphere filters out most UVC radiation.
UVA and UVB
For our purposes, UVA and UVB are of central importance. UV light in the 315-400nm range is called UVA. UVA is thought to be important for the regulation of sleep, breeding, and appetite, as well as helping chameleons see properly by way of a the pineal gland. However, since any UVB light will also have a large portion of its illuminance dedicated to UVA, our main focus here will be on UVB, which occupies a small space on the UV spectrum of 280-315nm.
UVB and Vitamin D3
When exposed to UVB light, the skin converts a particular cholesterol (7DHC) into pre-vitamin D3. With proper temperatures, the skin then turns this pre-vitamin into vitamin D3 proper. Vitamin D3 regulates the absorption of calcium in the system, so no D3 means no calcium absorption. If vitamin D3 is not available, then it does not matter how much calcium you give your chameleon; it will be unable to absorb it. Since all muscle activity (including heart function) requires calcium, the body is forced to draw on its calcium reserves to sustain these functions. Those reserves are in the bones. As calcium is drawn out of the bones to sustain vital functions such as a heartbeat, the bones become weaker and weaker. Eventually, the bones break, or become so malformed that they cannot support the body. This is the painful affliction called metabolic bone disease. While this is a highly simplified account of a complicated process that involves several vitamins and minerals, it will do for now. With proper UVB lighting (and temperature/calcium supplementation), the body can continuously replenish its calcium reserves, and MBD is not an issue. This is why UVB lighting is so crucial. Indeed, UVB is so crucial that when I set up any indoor enclosure, I use a Solarmeter as my guide for branch placement and foliage.
The Two Sides of UVB
Before discussing bulb types, I should note that UVB radiation can be dangerous. It is these very same wavelengths of light that cause sunburn, and have been linked to skin cancer. That UVB light has this two sided nature--one bestowing health, the other damaging it--makes being able to accurately measure it so important. The only way to ensure that you have proper levels of UVB is with a device like the Solarmeter 6.5, which measures UVB in terms of the same ultraviolet index (UVI) that weather stations use.
The UV Index (UVI)
As mentioned, the Solarmeter 6.5 measures UVB light in terms of the UV index. Lower numbers indicate lower levels of UVB light. At noon, near the equator, on a clear day, in full sun, at sea level, the UVI produced by the sun can surpass 12 or 13. Here in Southwestern Ontario, during the summer, I have measured UVI of over 11 in full sun. To be sure, wild chameleons are not out basking in such conditions, and according to health experts, neither should we be. When kept outdoors, my chameleons wake up and bask in the morning sun, where they receive a dose of UVB at a UVI of 2-4, then spend the rest of the day moving in and out of leaf cover, getting dappled sun with higher UVIs, hunting and going about other chameleon business. This seems congruent with the work done by Pete Hawkins and Bill Strand, who have shown that a UVI of 3 in the basking area is both safe and sufficient for a healthy chameleon without supplementary D3. Unfortunately, long term data about the negative effects of higher UVIs (above 6) is not as readily available. But this seems sufficient for a start. Regardless of the shape of your enclosure, you need to create an open area in the top portion of your enclosure where your chameleon can bask and receive UVB light in the 2-4 UVI range. Perhaps the highest branch will be UVI 4, while the next highest is UVI 3, and so on. I will discuss this in more detail in the section on setting up an enclosure.
UVB Bulbs
There are number of bulb types that produce UB light. Compact fluorescents, mercury vapour, metal halide, T8, LED and T5 high-output fluorescents. While all of these produce UVB light, not all will work in tall cages with animals that can reach lengths of 20".
Compact Fluorescents
Compact fluorescents come in two forms: the spiral, and the U-shaped.The spiral types are almost useless for standard chameleon cages, and the U-shaped are not much better. The problem is that, mounted in a vertical position, both bulbs produce intense UVB light within an inch of the bulb, but within 8", e light they produce is negligible. Worse still, they do not spread the light horizontally. Instead, they focus all their power on a small area. The u-shaped types can be mounted horizontally, which will spread the light out slightly more, but all-in-all these are not appropriate lights for most chameleon enclosures.
High Intensity Discharge
Metal halide and mercury vapour lamps (both high intensity discharge bulbs) throw out a ton of UVB; but again, the light is focused rather than spread out over the entire length of the enclosure. Of the two, metal halides are far superior, in both quality of light and application. However, the heat produced can be dangerous, and I would recommend these bulbs only to advanced keepers.
T8 Fluorescents
T8 bulbs used to be the industry standard. They have the benefit of spreading the light over longer areas, but are weak, and require branch placement within a few inches.
LEDs
While LED technology has come a long way, there are very few dedicated UVB emitting LED bulbs. They exist, but they suffer from all the same problems as the compact bulbs: they just don't put out enough light over enough distance to be useful at this point. My guess is that this will change over the next five years, or so.
T5 Fluorescents
T5, high output, fluorescent bulbs are by far the most applicable UVB source for chameleon keeping. They produce intense UVB light in a range of strengths, and the light is distributed over the entire length of the cage. They come in sizes that match all of the most popular cage sizes. Currently, these are the only UVB lights we recommend for most chameleon applications. There are several brands of T5 high-output, UVB bulbs. The two most well know are ZooMed's Reptisun 5.0, and 10.0, and Arcadia's line, which boasts bulbs at 6%, 12% and 14% UVB. Please note that using a proper reflector within the T5 fixture will greatly increase the efficiency of the bulb. Again, a UVI of 3-4 in the basking area has been shown to be both safe and effective, so whatever fixture/bulb configuration you choose, please ensure you are getting the UVI numbers in the basking area with the use of a solarmeter.
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Daylight
Providing  bright full-spectrum light is crucial both for proper plant health, and the general well-being of your chameleon.
Canadian keepers have the disadvantage of a winter season with very short days. This is especially true for more northern cities, where dawn can be as late as 8 am, and dusk can begin by 4 pm. Even enclosures placed by a south facing window will not receive sufficient light to support vigorous healthy plants. And while your UVB bulb will supply a small amount of light, a proper enclosure will need supplemental daylight. Daylight bulbs come in a number of forms, but all will deliver bright white light in the 6500 kelvin range. The two most important forms for us are LEDs and T5 high output flurescents.
LEDs
LED technology has come a long way in the last decade, and full-spectrum daylight LED lights are not only readily available, but can put out more useful light with less electricity than their fluorescent cousins. More recently, some companies have created T5 LED bulbs that will fit in a normal T5 fluorescent fixture--a boon for anyone using a multi bulb fixture. In a four bulb T5 fixture, you can combine a T5 UVB bulb, and three T5 LED conversion bulbs for a massive amount of light. Other panel-type LEDs are also excellent options. Please make sure that whatever LED you chose provides a full-spectrum daylight. LED panels that mix blue and red diodes are not recommended for chameleon enclosures.
T5 High Output Fluorescents
Next to LEDs, these are the most popular daylight bulbs. They can be used along side UVB bulbs in multi-bold fixtures, and depending on how many are used, there may be no need for an additional basking bulb. I have found that a 4-bulb T5 fixture with one UVB bulb, and 3 daylight bulbs produces sufficient heat to maintain a good basking temperature of 27-28 degrees C (80-82F). Please note that the best T5 fixtures have individual reflectors for each bulb. Please see the equipment section for brand suggestions.
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Heat Lamps
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While basking and temperature regulation is an important aspect of chameleon husbandry, the current trend in captive care is to provide additional basking heat for a few hours/day, rather than all day-long. Â This trend is tied into the movement towards replicating natural conditions--the relevant ones being that wild chameleons bask primarily in the morning to recharge their batteries, spending the rest of the day in partial shade.
Heat Lamps, or basking lamps, are used to create a warm area where our cold blooded chameleons can warm up. Unlike some other reptiles, most commonly kept chameleon species do not require excessive heat to bask. For veiled and panther chameleons, I have found anything above 28 degrees C to be unnecessary. Indeed temps above this can make it difficult to keep lower parts of the enclosure in the preferred range of 22-25 degrees c (72-77). Please note that chameleons are not flat, and if the temperature of the basking branch is 82, then the temperature on your chameleon's back (or casque, for veileds) might be significantly warmer. My preferred method of avoiding dangerous temperatures and burns is to fix the remote probe of a thermometer on the backside of the basking branch, so it is out of view, but still under the basking light. I then measure the temperature approximately two inches above this with a heat gun, or additional remote probe, and position the basking bulb so as to heat this area up to 28c (82f). Then I compare this temperature with the temperature of the probe on the basking branch. For example, if the temperature in the actual space where my chameleon will be (approx. 2-3" above the basking branch) is 28c (82f), and the probe on the basking branch reads 26c (78.8f), then I have a baseline temperature. That is, if my basking branch temperature is 26c, I know my basking temperature is 28. And since my basking branch probe is permanently in position, I just need to make sure that my basking branch temp stays around 26c (78.8f). Of course, it would be a lot simpler to simply suspend the temperature probe exactly where your chameleon will be, but most people don't like the aesthetics of an artificial probe dangling in the cage. Given these considerations, there are two broad categories of basking lamps that are useful to us.
Regular Incandescent
A regular 40-60 watt incandescent household bulb in a cone-shaped reflected fixture is often all that is needed. Simply turn it on, and position it above the basking branch at what ever height delivers the appropriate temperature.
Directional/Internally Reflected Halogens
Halogen bulbs get hot! However, due to the the internal reflector built into some halogen bulbs, they can project their heat in a particular direction rather than just straight down. This can be extremely useful where space above the enclosure is tight. A directional halogen heat lamp can be mounted to a wall, or dedicated stand to the side of an enclosure, and its "hotspot" pointed towards that basking area. Often times, the more focused nature of the these lights means that lower wattages can be employed to great effect. I have used 35 watt versions that were able to create ideal basking temperatures when mounted at a tangential angle over a foot away from the top of the cage. That being said, these are trickier bulbs to use, and extra time needs to be spent to dial in the temperatures.
Dimmers
Unlike many fluorescents and LEDs, both incandescent and halogen lamps are dimmable. That provides an extra opportunity for keepers to "tweak" their temperatures. If you're having a hard time getting the right basking temperature, using a dimmer on either of these bulb-types can help you make fine adjustments.
Enclosure Type
Your enclosure type will play a big role in deciding on a proper heat lamp, or even whether an additional heat source is necessary. For instance, with a 4-bulb T5 fixture over an all-glass enclosure, an additional heat lamp might not be necessary. All screen enclosures, on the other hand, might require a 60 watt bulb to maintain an appropriate basking temperature. The best way to accommodate this is to set up your enclosure first, then assess how much (if any) additional heat is required.
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