Do you know the CHDK? Canon Hack Developer Kit? For PS cameras, either lower or higher class it enables the RAW (DNG) mode and then you can process it as a DSLR, or more powerful camera. It can be reached at: http://chdk.wikia.com/wiki/CHDK Fotoos
CHDK let me capture this with an A590IS -- it has a motion detection mode that's sensitive enough to be used for auto-shutter on lightning strikes.
