I originally heard about hacking Canon digital cameras before I even knew what a high altitude balloon was. So when I started planning for my balloon launch, I knew it would be the perfect way to control a camera at 100,000 feet. The Canon Hack Development Kit (CHDK) is nothing more than software loaded on a camera’s memory card that adds additional functionality.
I did a little eBaying and found a Canon SD450 for a great price. Luckily I didn’t get ripped off and the camera turned out to be in great shape. The FAQ page has a list of supported cameras and their supported firmware versions. Unfortunately, it can be impossible to check the firmware version when buying a camera online. Most popular firmwares are supported so I can’t imagine it being much of a problem. Buying an older model helps with this too.
Once you have a supported camera, just head to the CHDK download page and grab the latest version. The ‘small’ version is all you need for high altitude photography, so grab that. Then follow the instructions included in the download. They are very straightforward and easy to follow. Make sure to set CHDK to start automatically on power-up to make your life easier.
The most useful part of CHDK is the ability to run scripts. Scripts are little programs that can run on the camera. You can even write your own if you want. For the HAB project I downloaded the Ultra Intervalometer script. By download, I mean copy and paste the code into a text file, save it with a .bas extension, and copy it into the CHDK/SCRIPTS folder on the memory card.
The Ultra Intervalometer script allows a custom interval to be selected for the camera to take pictures at. If the number of pictures is set to infinity then it will take pictures at the interval specified until the battery runs out, memory card fills up, or the shutter button is pressed. This is perfect for high altitude balloon photography. ‘Script Autostart’ should be turned on from the scripting parameters menu so the script runs automatically when the camera is powered up. Once everything is set up, it’s just a matter of turning on the camera and verifying that the camera is taking pictures.
One caution: Make sure you have a camera battery that can last as long as you expect the flight to last, or at least until the balloon bursts. It’s worthwhile to perform a test run until the battery runs out so you know it can last as long as you need it to.
Leave a Reply