Dry conversion lens as wet lens?

[Wisnu]

There’s must be strong reason when people spend hundreds buck for wet lens – so this may be a stupid question.
My friend give me a cheap 58mm WA lens + macro conversion lens – consist of a removable macro dioptre +10 and 0.45 WA.
Since I get it for free , I am thinking to use it for my underwater camera, ie. Oly SP-350 in PT-030 housing (46mm port) unless somebody can tell me this is something ridiculous to do and totally useless.
There’s an air space between the macro and WA lens. No leakage from the screw connection when I filled with water. I am not sure if can withstand high pressure. But typically I dive in shallow water less than 15 m.


cheers

 

[Gombessa]

There’s must be strong reason when people spend hundreds buck for wet lens – so this may be a stupid question.
My friend give me a cheap 58mm WA lens + macro conversion lens – consist of a removable macro dioptre +10 and 0.45 WA.
Since I get it for free , I am thinking to use it for my underwater camera, ie. Oly SP-350 in PT-030 housing (46mm port) unless somebody can tell me this is something ridiculous to do and totally useless.
There’s an air space between the macro and WA lens. No leakage from the screw connection when I filled with water. I am not sure if can withstand high pressure. But typically I dive in shallow water less than 15 m.

I've kind of wondered this as well, since above-water 67mm wide angle lenses can be found dirt-cheap. However, I imagine in a multi-element lens, the issue is water seeping into the lens housing itself between the lens elements (or crushing the glass), rather than the air space between two screw-in lenses (which would almost certainly flood at any depth deeper than a bathtub without an o-ring seal). On an UW wide conversion lens, it's actually a wet lens and is designed to let water in between the housing and the lens.

 

[MauiScubaSteve]

If you have a port / housing that accommodates your entire rig, a dry conversion lens / combination of lenses should work just fine. They are designed optically to work with a layer of air between the two glass surfaces

A wet wide angel lens, or wet macro lens, is designed optically to have a layer of water between the port glass and the conversion lens glass. There are two nice results from this approach; you can take the lenses on and off during the dive and the camera housing can be significantly smaller..

It's highly likely that some photo dives have involved changing from one macro lens to two macro lens to stock housing to wide angle lens. That is only possible with "wet" lenses.

 

[Nemrod]

The lens will flood and of course be ruined as a result.

As well, wet conversion lenses often have optical or hard coatings designed to live in the water as well as being sealed and designed for operation under pressure and of course being at least partially corrected for use in water.

Dry conversion lenses can operate in a dry port system effectively, of which there have been a few here and there, I think 10Bar has a system with the GF-1? maybe?

Wet conversion lenses can usually be swapped or removed underwater for differing perspectives a dry port of course cannot.

N