The wide angles: Think of it like a "cone" of view. A wider angle lens (smaller mm, like 28 mm) has a wider "cone" than less wide (bigger mm, like 35 mm). On the telephoto side, a bigger mm (135 mm) acts like a higher magnification (bigger telescope, bigger binoculars) than a smaller mm (100 mm).
Underwater, the effect of having a housed camera (air in housing) in a wet environment is to
increase the net mm, so a 28 mm lens acts like a 35 mm underwater; a 35 mm acts like a 45 mm, etc. (This is a very rough statement; purists please don't jump on me
)
f/#, e.g. f/2.0, f/2.8, f/4, f/5.6 etc. refer to the aperture. I think you had a question about that. Both lenses open to f/2.8. Smaller f/# mean larger aperture (go figure), which means that they let more light in to the CCD chip. The disadvantage is that (again, very roughly), a small f/# (or large aperture) has less depth-of-field, meaning that a smaller span of distances appear in focus. If I'm shooting a fish at 1 m distance at f/2.8, the zone from about 0.9 to 1.1 m will appear in focus (more or less). If I'm shooting the same fish at 1 m, at f/16, the zone from about 0.6 m to 2.5 m will be in focus. (Actually, the wide angle also plays into that; wider angle has better depth-of-field). For macro shots, for example, it's very nice to set a wide aperture (small f/#) and focus on your subject. Then, foreground and background are blurry. For fancy landscapes (or seascapes), it's nice to set a small aperture, so that a lot of the background (essentially, to infinity) appear sharp.
Now that we understand that you actually have
both cameras (are you sure we can't talk you into trading in your gf
?) and are just trying to understand which one to house...
How much do you think you want to get into UW photography? If you're pretty serious about it, I'd probably say the 5060, so that you can shoot raw & easily photoshop-it (you can also photoshop jpegs, although the purists would not like me to say that
) and get a hot-shoe-able-strobe (TTL strobe).
But, on the other hand (I must be an octopus
), purists also don't like TTL strobes, and like to set strobes to fire manually...
On yet another hand, the new Inon D2000 strobe looks like it can TTL point-and-shoot cameras pretty easily.
If TTL strobes haven't been explained to your satisfaction, let us know; I'm sure lots of folks here will be more than happy to enlighten you (pun intended)
