Canon A2200 NIR conversion
This past weekend during LEAFFEST, under the watchful eye of Jeff Warren, I converted a Canon A2200 camera to capture near infrared (NIR) images using a technique similar to the video Jeff Warren did for the Canon A490. The A2200 has a good review by a company that does professional NIR conversions. Some nice features are that it has a custom white-balance option (can provide images without the strong bluish hue common with many converted cameras) and it does not have a hot spot (bright spot on the image) which is a problem with some camera models. There is not a final release of CHDK for the A2200 but I've been using the beta release and have not had any problems with basic functionality. The firmware is recent enough to be able to handle SD cards larger than 4GB without any special (and cumbersome) formating. Another feature that someone else highlighted is that it uses the older (and more common) 4-pin USB port for data and CHDK communication and a 3.5 mm stereo audio plug for video output. Some newer Canon cameras use an 11 pin USB for video and data. Some other good features are that it's small, light and takes decent photos.
Below is a short guide intended to help someone interested in this conversion. Before trying a conversion I suggest that you look at Jeff's video to get a good introduction to the whole process. It's important to work in a clean environment to avoid getting dust in the camera. It's also good to keep the screws in a container or on a piece of tape so you don't loose them and keep them organized so you can put them back in the proper holes when you reassemble the camera. When unscrewing the screws make sure the screw driver (all screws have a phillips head) fits nicely in the head of the screw or you risk stripping the head.
If you have comments about how to make this a more useful guide please let me know. In a few weeks I'll post a comparison of different NIR converted cameras including a couple that were professionally converted.
The first step is to remove the back part of the camera case. Remove the four screws as noted on the figure below. Once the screws are out try to pry the back part of the case off with a thin flathead screwdriver or something similar. The case on my camera had a tight fit but after moving the screwdriver around a few times it popped off.
Remove the four screws that attach the display screen to the camera body then gently (you don't want to tear the brownish cable) move the display out of the way of the sensor circuitry.
Remove the three screws that attach the sensor circuitry (mounted on an aluminum plate). This takes a little work since there is a drop of hot-glue on each screw. Using moderate down-pressure on the screw and a good fitting screwdriver the hot-glue popped off as I was unscrewing the screws. You might be able to pry/pop off the glue with a small flathead screwdriver before unscrewing the screws. After the screws are removed gently pry it up and out of the way so you can access the rubber gasket under the sensor. You do not need to unsnap the wire harness connected to the sensor circuitry, just move it out of the way. As I was lifting the sensor circuitry I broke one of the plastic posts that help guide the sensor circuitry into place. I don't expect that's a significant problem but something to try and avoid. Do not put your fingers on the sensor or the hot mirror.
With the sensor circuitry out of the way you will be able to remove the rubber gasket that secures the hot mirror over the camera's optics. You can use a pair of tweezers to carefully pull the gasket up and out. The gasket does not appear to be all that strong so carefully working around the gasket seems wise. Once the gasket is out the hot mirror should be loose. It might fall out just by turning the camera over or you might need to gently pry it a bit. It's a good idea to save the hot mirror without putting finger prints on it in case you want to put it back in the camera at some point.
The next step is to place the developed film cut to match the size of the hot mirror into the same place the hot mirror was housed. Once that is done the camera can be reassembled. Putting the sensor circuitry plate back took a little coaxing since the remaining hot glue pieces got in the way. I pried the hot glue off with a flathead screwdriver to make more room. The other reassembly steps were straightforward.