I have two canon cameras. An a2300 and a3100 loaded with CHDK and KAP script.
The settings on KAP scripts are, for both cameras, to use the lowest shutter speed and ISO 100 or 200.
The aperture is evaluated using the EV in a sunny day.
I tried my first map but I got very bad images compared with the images shooted in Flight Riot camera settings youtube video.