Random Geekisms: The PC Dust Filter Case Mod

Dust bunnies have been the bane of computer geeks for almost as long as there have been PCs, and for good reason. It only takes a few months for enough dust to build up in the computers for the fan to get noisy or the OCD to kick in and so computer geeks find themselves constantly having to to open up the cases and vacuuming the filthy mess inside to keep things running smooth. For non geeks, it's even worse because they have never seen the insides of their computers, and are often left wondering why they have to buy a new computer every few years when their fans crap out or computers overheat. The solution is incredibly simple but rarely effectively employed. All you have to do is filter the air coming into your computer. Some computer/case manufacturers use some kind of filter, but usually it's not much more than wire mesh which is only marginally effective. However it's possible to mod your case to efficiently filter the intake rather easily and inexpensively with just some basic tools and a little elbow grease.

Here's what you want in your filtering system:

1. As much surface area as possible for the filter. This allows for less constricted airflow and lessens the allows the filter to be used longer before clogging.


2. Most computers/cases are designed so that the airflow through the case passes air over the hard drives and CPU before exiting. You want to maintain this too keep your drives and CPUs from overheating.

Here's how it will look (excuse the graphic :o)

Basically you can use the 2 styrofoam blocks that likely came with your case/computer to prop up the computer and hold the filter. The air will pass through the filter, into a slot on the bottom of the case near the hard drives, over the drives cooling them, then the CPU, and out through the back fan/power supply fan.

The first step is to cut slots and holes on the bottom of the computer case to allow air to be drawn in from the filter below. Make sure the slots are positioned so that the air entering the case will have to flow over the hard drives. This was an aluminum case so I used a Dremel tool with a cutting bit to create the slot, then a large drill bit for the holes.

Next, cut out the insides of the styrofoam blocks. Again I used a Dremel tool. The top block is used to seal the edges of the computer as well as create a gap between the bottom of the computer and the filter. This gap allows the air to be drawn over the entire filter, without the gap air will only be drawn through the part of the filter near the slots on the bottom of the case.

Cut some arches in the bottom block like you see in the first photo above so that air can pass underneath. You might also want to cut the styrofoam so you leave some some cross members in the block to keep the filter from bunching up into the gap created by the top block.

Next go to the hardware store and buy some electrostatic air filters which you can cut to size. Cut the filter to fit the bottom block and staple it to the bottom. If you get the foam/fiber filters like I have here, make sure the foam is on the outside so it is the first to filter the air.

Next seal off any holes in the case to make sure air doesn't get drawn into the case anywhere but through the filter. I just used clear tape to cover various holes and gaps:

Next cover your computer's existing air intake with another piece of filter. Here I sandwiched the filter between the case and the front cover, over the original intake.

Put everything back together and there you have it. It may not be pretty but it works!

How well does it work? I built this computer 4 years ago, I only vacuumed it once and that was 2 years ago. It's still almost spotless inside:

Compare this to what some computers look like after a few years!

Don't be that guy.

Another added benefit is that you've also turned your computer into a rather decent HEPA air filter which will help to remove dust from your digital darkroom, good news for those of us who still scan film.

For maintenance, all you have to do is vacuum the bottom of the filter every couple of years, and really, you don't even have to do that.

Photographing under fluorescent lights

When out taking photos under fluorescent lights, you may have noticed weird things happening with your images such as the color temperature and/or exposure shifting between frames even though you haven't changed your settings. Here's an example of what it might look like (photos were taken in rapid succession in Manual mode):



The reason for this is simple, fluorescent lights flicker. Too fast for your eyes to see, but depending on your shutter speed, your camera may be able to pick up the fluctuations. If the light uses a magnetic ballast, it will flicker "off" 100-120 times a second (2 times for every cycle of the 50-60Hz line power). At high enough shutter speeds, one frame might be taken while the light output is at its peak, and another frame taken while the light is at its lowest resulting in significant exposure differences. At slower shutter speeds, the fluctuations end up being integrated together so you won't notice a difference between frames.


The good news is many if not most fluorescent lights you encounter now use electronic ballasts that operate at 10kHz or more, which means the flicker is too fast to be a problem for normal shooting. Under magnetic ballasts, you can try to use a lower shutter speed and/or bracket and this will usually solve the problem.


One interesting note is many people are noticing this phenomenon for the first time with digital cameras and think it's an issue with digital. This is a misconception of course because the same exact thing will happen with film. The only difference was back in the film days, we rarely shot with film above ISO 400 or 800 because the photos would look too grainy. Digital cameras now however have so little noise (some DSLRs like the Canon 5D Mk II or the Nikon D700 produce images at ISO 6400 that look better than some 400 speed film!) that people often shoot at high ISO settings all the time, which means higher shutter speeds that better reveal the flicker. Also with digital we shoot more frames because it doesn't cost anything and can instantly review the image so more people are noticing the problem. If you see it though, don't worry and don't return your camera, just follow the advice above and keep shooting.