...How good shots can you get without a strobe (using a point-and-shoot)? Are there any strobe-less guides available?
How good you consider your resulting shots to be depends on how particular you personally are (for "good"), and the waters that you'll be diving in. The biggest problem with 'no strobe' P&S photography is that you're not going to have the strobe power to restore the full light spectrum for those photos where you want the full spectrum, because post-processing can only go so far.
What this means is that if you're taking natural light photos of a big shipwreck (where you want to be monochromatic), you'll be turning off your internal strobe anyway, so you'll do fine.
Similarly, if you're taking really close in macro photos, the P&S's built-in strobe (if available) can usually be adequate, particularly with post-processing. FYI, having less ambient light is usually helpful here.
The lack of a strobe is basically a problem in the middle ground ... photos of people portraits & fish at 2ft - 4ft range. You basically try and then hope for the best with post-processing results. What does help with post processing is to be shooting in shallow depths (<30fsw) and in gin-clear water ... basically, to have some red channel naturally present to be able to boost in post-processing. Here's an example:
Original, as taken (Canon A70 P&S):
After Post-Processing:
FWIW, I was lucky in that the above turtle was quite shallow: he swam under me as I was approaching my safety stop, so probably only 30fsw depth or so...but even so, notice how the post-processing affected sandy bottom background (blown out whites).
The same shot with some more examples are located
here - and the images in the beginning (bracketed between the B&W images of the Nikonos camera system) are from this digital P&S without an external strobe, whereas the images in the second half are digital scans from 35mm slides taken with the dual-strobe system in those B&W photos...hopefully gives you an idea of the difference in potential. Note the differences in image compositions: a lot of the P&S images were macro- and also "under ledge" to block ambient sunlight. One that isn't is the 2nd photo which I chose to leave as Natural Light: this was at ~60fsw and despite the internal strobe, there simply wasn't enough red channel to boost in post-processing to get up to the true color fidelity close without bringing up horribly overt "red speckles" noise.
Anyone have S95 photos without a strobe, and anyone recommend the manual settings (aperture, shutter speed, iso, etc.)?
No settings offhand, but I'd be inclined to recommend that you let the camera do most of the work of exposure optimization. There's some trade-offs, but what you want to prioritize having personal control over is the camera's internal strobe (forced on/forced off ... try to avoid the randomness of 'automatic') and if the camera has a Macro button. Similarly, you probably want to avoid any auto-ISO feature and force the camera to a modestly low ISO setting, such as 100...UW backgrounds can be a void that fools TTL systems and high ISO gets noisy fast.
Finally, a partial solution could be an old strobe that's triggered via a slave sensor off of your internal flash. I used one of these a few years ago (a "salvage" setup from some flooded equipment) with a quite powerful Ikelite SS-200 strobehead and found that while I could make it work, it was back to the very old days of UW photography where you only had manual settings for everything and you needed to be very studious in controlling your distance-to-subject for your strobe lighting path while remembering all of your photography fundamentals for exposure.
Hope this helps,
-hh
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