noob question on P&S wide angle wet lenses

[BSOD]

I'm sure it's a really basic question, but I've tried a bit of searching and couldn't find the info.

How does a wet lens work? Not in terms of the optics/etc, but just physically attaching it to your housing (whether via bayonet or thread mount). Does it need to be attached while underwater, so there's water between the glass of the housing port and the back of the add-on lens? Or is it open/vented such that if you attach it while dry, that space will fill up with water once you're wet? (in which case how would you ensure you don't get air bubbles stuck between the port/lens)

Will a fisheye/wide-angle lens also work okay (understandably not great) for macro or would it need to be removed?

I've seen mention that for dSLR's, in some situations/setups you need to focus a short distance away on a virtual image (created by the dome/etc) - is that the same case for something like the FIX UWL04 fisheye or Inon fisheye/dome lens/unit?

Can an over/under shot be done with a flat wide angle lens (like an Inon uwl-100 or Ike W20), or does it basically need to be done with a dome?

Thanks in advance

 

[Nemrod]

I'm sure it's a really basic question, but I've tried a bit of searching and couldn't find the info.

How does a wet lens work? Not in terms of the optics/etc, but just physically attaching it to your housing (whether via bayonet or thread mount). Does it need to be attached while underwater, so there's water between the glass of the housing port and the back of the add-on lens? Or is it open/vented such that if you attach it while dry, that space will fill up with water once you're wet? (in which case how would you ensure you don't get air bubbles stuck between the port/lens)

Will a fisheye/wide-angle lens also work okay (understandably not great) for macro or would it need to be removed?

I've seen mention that for dSLR's, in some situations/setups you need to focus a short distance away on a virtual image (created by the dome/etc) - is that the same case for something like the FIX UWL04 fisheye or Inon fisheye/dome lens/unit?

Can an over/under shot be done with a flat wide angle lens (like an Inon uwl-100 or Ike W20), or does it basically need to be done with a dome?

Thanks in advance

There must be water between the lens and the port, some lens adapters are self venting and others need to have the lens burped to remove trapped air. BTW, some wet lenses work fine for surface use and others are corrected for underwater use only, what you don't want is both air and water (bubble/bubbles) between the port and lens as they definitely show up and ruin the photo.

A fisheye lens can do what is called close focus, wide angle perspective photography, to do macro you will have to remove the lens.

The virtual image, there is some disagreement on this subject, I have never needed to focus on a virtual image either with a film SLR or my current Canon S90 with various wide angle and fisheye dome lenses. YRMV

Yes, you can do an over/under but the problem is that the smaller the dome the more difficult it is and as well with a wet lens, the water will drain from between the port and lens, so yes it can be done with some efforts.

N