Various software resources for adding timelapse, synchronization and auto-exposure bracketing (AEB). Updated 29/3/11
CHDK – Canon Hack Development Kit
CHDK is what makes this project possible at all. Some very clever people have reverse engineered the operating systems of some of the Canon PowerShot and Ixus compact digital cameras and enabled a number of enhanced modes as well as programme control using uBASIC or LUA.
CHDK enables triggering of the shutter via low voltage pulses on the USB port. There is a circuit diagram of a simple remote shutter on the CHDK Wiki.
However, unlike the instructions state here, you do not need to be running a script, or in <ALT> at all once remote triggering has been enabled.
There is a bug in CHDK that causes the software to malfunction if the auto-exposure-lock (AEL) is engaged, although the auto-focus-lock (AFL) does work. Cameras that are largely automated, such as most compacts, can introduce a fluctuation of exposure levels due to the stepping auto-exposure settings. This can cause an unacceptable flickering in the final movies. The use of an external trigger (operating in the camera’s normal mode) allows use of both AFL and AEL to be engaged at the same time.
A good example of why it is desirable to lock the exposure is here:
Justin Majerczky is quite apologetic about it being a bit obvious, but it is superb. It might be possible to lock exposure within CHDK but I am not there yet.
Another Canon hack that I have only just heard about is the 400plus hack for the EOS 400D. It just so happens that I have one of those and two of the additional functions enabled by it are increased range in exposure bracketing, and time-lapse interval shooting. Both of these functions are of particular interest to me. The time-lapse obviously but I sometimes find that the basic auto-exposure bracketing (AEB) on the 400D is too limited for capturing multi-shot HDRs. By default, the 400D will take 3 shots and a maximum exposure compensation of +/- 2 f-stops, which is not always enough dynamic range. With the 400plus hack, the 400D can shoot up to 9 shots with a range of +/- 6 f-stops. Also, according to the documentation, these 2 modes can be used together and so will allow me to shoot HDR time-lapse movies without a timer remote.
gPhoto2 is a LINUX library of commands to control a wide variety of digital still cameras, not just the Canon Powershots.