Some of the stuff lapser did last year will let you adjust exposure "on fly" in continuous mode and IIRC correctly get you into the 1fps range. Some of his customizations have since been added to CHDK and reyalp is apparently working on others.
The exposure can be adjusted on the fly, the hard part is knowing what it should be.
Using the the current CHDK 1.3 trunk, you can get reasonable exposure using the existing shot_histogram function in conjunction with shooting hooks. This can be done either in continuous mode or using the "hold half press, click full press" approach of the "fast hdr script" mentioned in this thread
http://chdk.setepontos.com/index.php?topic=11527.0If Kozuch is analyzing the images externally after each shot, that could also be used to decide the next exposure.
It's also worth noting that many cameras have a reduced resolution "low light" or similar mode which is substantially faster than normal shooting. These will probably get a fair bit over 1 FPS on most cameras, but because these modes don't use a standard raw buffer, shot histogram will not work correctly.
Could the continuous mode go on forever? No buffer or writing to sd problems?
In general, most powershots will shoot continuously at about the same rate until the card files up. A few have special burst modes that behave differently.
Are you planning to do your computer vision stuff on the camera itself, or on some external device connected to the cameras USB?
Doing any significant processing on the camera itself will be problematic, because the CPU is quite slow.
If you are using a separate system to analyze the images, you can use PTP remote shoot to save the data directly over USB. However, the camera still allocates some resources for each shot so you can't shoot "forever" without rebooting. Also note that some ports have problems with remote shoot
http://chdk.wikia.com/wiki/User:Nafraf/RemoteShootIssues and some do not have remote shoot fully implemented.
