Does anybody find the noise in the S2 worse than with the S1? I have not done extensive comparisons, but sometimes I get this feeling like the S2 is noisier. Especially taking video's in low light. Can't have it all I guess...
For fireworks, you should probably use a tripod and shoot in manual mode for best results -- the built-in IS probably won't help enough. And expect to shoot a lot of shots to come up w/ a few keepers as timing is an issue.
Generally, you want a shutter speed between 1 to 2 seconds, depending on your preference. And depending on the chosen shutter speed, you'll want to vary your aperture and ISO combo to be around f/5 (give or take a little) + ISO 50 -- I imagine somewhere between f/4 and f/5.6 is the sweet spot of the lens, so this works out well.
I don't have the Canon S2 IS, but those shutter speed, aperture, ISO combos should get you in the right direction. Shoot a few shots to see if you get proper exposure, and then adjust accordingly. You may find that you'll need to vary the settings combos to expose 1 stop/EV or so dimmer in the climactic scenarios (or if you intend to go w/ a longer shutter speed to capture a longer moment). You may also need to vary the exposure depending on the color/intensity of the particular fireworks. And shoot in RAW, if possible, for best results since that'll allow you some extra latittude for post corrections in case the straight-from-camera shots might be overexposed.
For focus, you should just put it on manual focus and either focus to infinity or 1 step below infinity unless you're super close to the fireworks (and would need some serious super wideangle converter and maybe a good fire suit to boot ). The camera (and near infinity focus distance) should have more than enough depth-of-field for the fireworks under just about all practical scenarios.
Hmmm... I just checked the dpreview page for this camera, and apparently, it has some sort of "fireworks" scene mode. Maybe you can just use that to get what you want -- I'm pretty sure you'll still need a tripod though.
I took a slew of photos with my S2 over the weekend at a comic convention. Here's the photo album.
I pretty much got really lazy and shot in Auto mode, with or without flash, in well-lit and not-so-well-lit conditions. So this was somewhat of a torture test for the Auto mode for the S2.
In fact, I have decided to get this baby (S3) and pair it with a 4GB SD card. I am getting some extra pay for working the 4th of July, and damn, is it burning a hole in my pocket!