Hi,
Don't shoot in P mode as the camera will adjust it's settings to obtain it's best shot, i.e. f8 at 200th second is the same exposure as f5.6 at 100th, F4 at 50th all that will change is the depth of field, use AV mode instead and bracket 6 or more shots depending on the amount of shadow detail you wish to have clearly exposed.
Set your camera to AV on the dial, Turn off the Flash
Enter into CHDK - Extra Photo Operations,
Scroll down to Bracketing in Continuous mode, (scroll right)
Scroll down to AV Bracketing value enter 1 (more or less if you prefer, but this is a fair starting point,
Carry on scrolling down to Bracketing type and ensure it's set to +/-,
Scroll down and back out to normal camera operations. The info should be displayed on-screen
Click Function Set
Set iso to 80 subject to light conditions
Scroll down to Drive Mode, side scroll to C timer, you will then notice the DISP is highlighted,
Click on the DISP button to the left of the main MENU, here you can set the delay before the first shot is taken (1-30 seconds)not subsequent shots.
and the number of Shots (set to 6 in this example, you can go to 10) Click Disp to return to menu
Set your focus range to your preference and switch off the IS Mode if you are using a tripod or a solid base (especially recommended shooting HDR)
I would recommend Superfine and L settings.
You are ready to shoot.
Regards,
Papaone