Please note: This is the version that was posted online in early 2012. While the majority of the information presented here is still correct, there are a few things that are outdated. I've been meaning to update this for quite a long time, if you have any questions, you can click the Discussion tab and ask!
CFLs and Reflectors
The most common CFL used is the 23W Spiral. This is the actual wattage, not the equivalent wattage. There are a few different type of CFL lamps, and each one has a different ideal application. These are: spiral CFL, linear CFL, floodlight CFL.
A bare lamp will work without a reflector, but it will do the job much, much better with one.
The spiral CFL is definitely the most common type available and the most widely used. There are 2 ways to orient the lamp: with the end pointing at the screen or with the side facing the screen.
With the end lamp pointing at the screen, a reflector is a must-have piece of equipment. Without a reflector, a lamp pointed directly at the screen will do very little, since a small percentage of the light comes out of the end of the lamp. The cheapest, easiest, and most common reflector for this orientation is the dome-style reflector, which is available just about anywhere.
This reflector provides a wide light signature, since the side light is reflected to the front. They come in several sizes, and you want the biggest reflector you can fit in the space, relative to the size of the screen, that is.
The dome reflector does the job just fine, and one of these should be used at a minimum. However, it is by no means the ‘perfect’ reflector. The reflector has a ribbed, dull surface that does a good job of diffusing the light, but it is not as efficient as a shiny, highly polished spectral reflector. Also, about 1/4 or so of the lamp (depending on the brand) sticks out past the reflector, and most of that light does not get directed toward the screen.
Using several different sized round reflectors can be done also when space is a limiting factor, even though the smaller reflectors are not as effective. This is probably not an issue for very many people anymore due to the new screen sizing guidelines.
With the side of the lamp facing the screen, the reflector is usually a DIY job With a side-style orientation, more light is shed directly to the screen, but you still need to re-direct the light from the sides and back of the lamp towards the screen. There are a few fixtures that you can buy with integral reflectors, but most are very small. Most off-the-shelf light fixtures are for use in a shop or garage and have a half-round solid section, which may or may not have a reflector. If it does not, you can simply line it with aluminum foil or another highly reflective material.
The setup below uses off-the-shelf shop lights. The fixture on the left has reflective material installed.
The advantage to the side-lamp design is that since you can hang the lights from above, they generally take up less space (depending on your reflector) versus the dome reflectors.
In order to spread the light out evenly and wide (but not too wide or you’ll lose intensity at the screen), you want a wide reflector. Finding such a reflector is not easy. Since spiral CFLs can be considered a point source (more of a “blob” source, but this is for simplicity), using an HID reflector can be effective. A DIY beer can reflector can work also. Even some Mylar or aluminum foil will do the job.
Searching for a flexible reflector material and making your own reflector will yield the best results. A properly made reflector for a side-lamp orientation, such as the one shown below, can direct almost 100% of the light toward the screen.
Linear CFL lamps are commonly referred to as twin, triple, or quad tube, etc. They are similar in nature to Power Compacts in that the lamp is in a “U” shape, but commonly have an integrated ballast like a CFL. They are usually higher wattage than standard CFLs, are more intense, and can run hotter. However, since they use the screw-in base just like CFLs, they are easy to use and I have recently looked at a couple of nice builds using them, so I thought it was worth adding a section covering them.
Linear CFLs would be installed similar to the sideways spiral CFL, hanging the lamp from above. Reflectors are generally the same principle; however the source is now more linear, so your reflector in turn should follow the line of the lamp and curve around it. Here are a few of the better ideas for this that I’ve seen. One uses cut-up linear fluorescent reflectors, the other uses mirrored acrylic.
A reflector similar to the last one in the spiral CFL section could be done. Because the lamp profile is more linear, the reflector would be slightly different dimensions – probably more square than rectangular.
The floodlight CFL is simply a spiral CFL enclosed in a lamp housing like you would see for a standard incandescent floodlight. They are not very efficient at spreading light when placed in close proximity to the screen, as the light is diffused at the end of the ‘bulb’ and the reflector is of a small diameter. However, they are good for use on smaller, narrower screens – ones that have one dimension less than 6 inches. They should generally not be used for primary lighting, unless you are running a small Algae Scrubber. With the new screen sizing guidelines, the use of these CFLs for quick-and-dirty builds is a little more acceptable, but they are still relatively inefficient, so you will likely need to use more wattage than you normally would.
You can see in this picture that the floodlight only provides significant light to the area directly in front of the lamp – and that’s the only place that’s going to provide adequate filtration:
They can be useful in situations where space is highly restricted, but for larger Algae Scrubbers, more total wattage will likely be required over what would normally be needed.
They can also be helpful to supplement light from dome-reflector setups that just need a little more light but there’s not enough space for another dome.
One thing to remember when handling CFLs: install them gently. Most people are used to twisting in an incandescent lamp tightly. CFLs fracture easily at the base where the element (tube) meets up with the ballast. Cranking on them like causes these fractures. So if you can't grab on to the base to tighten, just get the lamp in there snug enough for the connection to be made. This goes for the lights in your house and office also - it's the #1 reason why CFLs burn out early.