What is CHDK? CHDK reputedly stands for Canon Hacking Development Kit. It is a type of firmware which temporarily resides on the camera's SD card. It can be booted automatically or manually each time the camera is switched on. It will only load when the camera is in the Playback mode. It runs in the record mode.
To date and to the best of my knowledge this firmware only runs on Canon Cameras. There is no equivalent for other camera makes.
So what does it offer? CHDK offers you the capability of being able to use features only found on more advanced Canon camera models. The ability to take RAW format pictures on the standard Powershot models for example. Naturally camera manufacturers like Canon build in redundancy and limitations in models for various reasons. One being that if we want a certain feature we would have to upgrade our camera and spend more money with them. Not an unreasonable desire.
CHDK does however offer the KAPper with some interesting avenues to explore and if you are interested in finding out more the best place is to go to the CHDK Wiki. Here you will find out everything you need to know about the subject.
One feature which stands out is the ability to be able to use a remote shutter facility via the camera's USB port and triggered by the voltage output from a RC servo channel. James Gentles has manufactured a USB/RC lead specially for this purpose.
I had the priviledge in testing the kit and subsequently wrote a QT movie on how to install and use the CHDK and lead on the Canon A640. You can view the movie HERE. Please note the movie will re-cycle the first 2 slides while downloading if you view it from the web, once done you can play the movie normally. This is a bug in either the Quicktime or its conversion from Keynote. You can download the zipped version HERE, which runs fine.
There are a few important ways in using CHDK. In particular it must be remembered that the CHDK resides on the SD card. Therefore with SD cards being relatively cheap it is possible to load your chosen scripts and configurations on individual SD cards. If you then program then to autoboot you have a very neat way of changing your cameras configuration quickly and accurately. Thanks to Peter Bults for pointing this fact out.
You must remember however that when loading CHDK the camera MUST be in the Playback mode, turning over to Record once the camera has loaded.
Some more thoughts and tips on CHDK
Check out James Gentles site.
Allows programming of camera through 2 RC channels.
Scripts available from GentLED site