Hehe... Thanks Kim
I may very well have misunderstood A LOT... After all I have never done any underwater photography and it is all a bit daunting still....
I simply read this
A full range of dome and flat ports is available to accommodate most macro, wide-angle and zoom lenses. Port attachment is quick and easy with a simple locking system and clear view of the port o-ring seal. Lens port not included. A large zoom control knob can be comfortably reached without removing your hand from the handle.
from the
Ikelite homepage
Ah......
No - you have slightly misunderstood what is going on.
A normal P&S digital camera is a single lens camera. However - it normally has a zoom as well which gives you a range of focal distances. Housings built for them are made to accomodate the maximum extension of the lens barrel - and therefore work at ALL lengths. To get "outside" of the camera lens itself..i.e. more macro, or more wide angle...wet lenses exist that can attach to the outside of housings that support them. Because they attach externally on the housing itself you can attach or detach them underwater, and therefore change lenses.
DSLRs are different. Here you buy actual different lenses that attach directly to the body of your camera - there is no native permanent lens on a DSLR. Now - lens are obviously all different sizes soooooo...... you need different "ports" to attach to the front of your housing, to accomodate the lens you want to use. You can't change this underwater. You have to choose before the dive which lens you wish to use (although it might also be a zoom lens with a range of focal lengths allowing wide angle to moderate zoom, including close focus macro capability....such as the Sigma 17-70mm). Different ports accomodate different lens - you can find a chart on the Ikelite site with listings of which lenses can be used with which port.
BTW - the lens I just mentioned...the Sigma... is a VERY useful lens for the 450D. I actually own this setup and use it as my primary walkabout lens topside. I haven't taken this rig U/W yet, as my Oly C5050 has been fine for the amount of chance I get to dive and use it.
FWIW - if you are just beginning with this, then I would really think about it. You might very well be better served with something like the Canon G9 and housing. That will cost you about the same as the price of the 450D body on it's own!
And you can do an awful lot with it!!!
I will probably get that myself soon, as the amount of diving I do that I can really use a camera doesn't really justify the expense of housing my DSLR. I take a lot of stuff topside, and I'd actually prefer to upgrade to the 5D sometime, rather than buy expensive casings that frankly probably wouldn't get me much better pictures than I can get with a good P&S with full manul controls, and RAW, such as the CanonG9.
YMMV. I'm not that rich!