A few weeks ago, I went on a liveaboard dive trip on the MV Caribbean Explorer (wonderful trip -- great crew and service, decent accomodations, good shipmates and diving...) and the captain, JF, had a Canon S30 with housing that I borrowed for a dive.
Some background:
I've been using a Nikon Coolpix 950 -- 2.23 mpixel -- in an Ikelite housing and a supplemental video light for conditions where natural light isn't good enough.
I've been thinking of picking up the Sony DSC-P5 (or -P9) with the Sony housing because of its small size (the idea being I could fit the housed Sony right in a pocket of my BC).
Thoughts:
Focusing
I think an autofocus camera is of marginal use underwater. Autofocus gets confused by particles in the water. If you're doing a nose-on portrait of a 6 foot reef shark from a distance of 3 feet, well, the autofocus will work just fine... but that's not typically what you'll be doing.
(Going into manual focus model should also dramatically reduce digital camera shutter latency, the delay that feels like minutes between pushing the shutter from half way down to all the way down and actually 'hearing' or 'seeing' the camera fire.)
The Canon can go into manual focus mode but I didn't get a chance to use it that way.
Natural Light
Let's ignore flash and supplemental lighting for a moment. In natural light photography under water, you really need an "orange" filter to help balance the adsorption effects of water. Without it, by time you're down 50 feet, all your pictures are blue, usually so blue you can't effectively adjust the color balance in your digital darkroom (PhotoShop, Photo-Paint, etc.)
Unfortunately, I haven't found an off-the-shelf "orange" filter assembly for the Canon-case. By contrast, Sony sells part number VFMP5K, its "Filter Kit for MPK-P5" (the underwater case for its DSC-P5).
Here's a link to Sony's writeup.
But, according to a post on wetpixel, "INON introduced their line of wide and macro attachment lens for the Canon WP-DC300/400 Underwater Housing at the Tokyo Diving Festival 2002. The INON lens adapter is compatible with the INON UCL-330 macro lens or the INON UWL-100 wide angle lens. Release date is May 2002."
Here's one thread I found on the subject.
This needs some more research.
If you can get an underwater color contrast enhancing filter (i.e., orange) for this housing, you ought to be able to take some decent underwater natural light pictures. (The filter, BTW, needs to cover not only the lens but also the light meter port.)
If not, natural light photos below 33 ft/10 m will likely suck. And at 50 to 60 ft or worse, you won't be able to do any reasonable digital manipulation to fix the color balance. (The depths here are guesses...I didn't really measure this in detail. This is "directional" advice...)
Unnatural Light -- Flash or Video
Given the way this camera's flash works, I'd lean towards using a video light where illumination was too poor. For example, you can pick up Ikelite underwater video lights through B&H Photo in NYC but none of this stuff is cheap.
With a good color filter, at reasonable depths, you can get some good natural light pictures (esp. on bright sunny days -- don't try this at night...) You don't need or want the color filter if you're using artificial light, either a video light or a strobe.
Suggestions:
1. Before buying the case, try the Canon on dry land, working it in manual focus mode on small and objects 1 to 5 feet away. If the manual focus works smoothly enough, OK. This is probably a cool combo for natural light photography.
2. If you find a good color contrast enhancement filter assy for the camera, you can probably dive deeper on colorful reefs and catch a lot of the color in the picture (assuming it's bright sun, etc.)
I'm in a quandry. The Canon seems to be a much more capable camera than the Sony. Don't know what to do. So I'll just keep using my Nikon...
