Fitting Wide-angle lenses underwater

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Postby Hintermann » Mon Mar 14, 2011 12:40 pm

I have a Canon S95 with a Canon housing, to which I have fitted an Inon LD28 bracket to take the wide angle lens. I am aware that there has to be a film of water between the housing lens and the back of the Inon. I was proposing to fit the lens inside the cleansing tank of the liveaboard boat before each dive. But the local UW camera shop staff tell me that the water might drain out when I take the ensemble out of the tank and so I really need to do it at the start of the dive in the sea. My worry is accidentally dropping the expensive lens, which is very negatively buoyant. I would rather not have to fiddle with the lens during the dive for that reason.

What they said did not make sense to me for 2 reasons:

1. If the lens fitting is watertight, then the water should not drain out when I take the ensemble out of the tank and so I should be OK.

2. If the lens fitting is not watertight and the water does drain out, then the pressure of the sea water should force water back into the crevice between the lens and housing.

Any thoughts on this?
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Postby Leendert Smit » Mon Mar 14, 2011 1:33 pm

I have the same sort of set-up as you and I always put my wide angle lens on before the dive. My bracket has at least one tiny hole to let water in and air out. You should check however if tiny air bubbles remain in the space between the lens and the port. It happened to me occasionally.

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Postby bvanant » Tue Mar 15, 2011 6:09 pm

Hintermann wrote:I have a Canon S95 with a Canon housing, to which I have fitted an Inon LD28 bracket to take the wide angle lens. I am aware that there has to be a film of water between the housing lens and the back of the Inon. I was proposing to fit the lens inside the cleansing tank of the liveaboard boat before each dive. But the local UW camera shop staff tell me that the water might drain out when I take the ensemble out of the tank and so I really need to do it at the start of the dive in the sea. My worry is accidentally dropping the expensive lens, which is very negatively buoyant. I would rather not have to fiddle with the lens during the dive for that reason.

What they said did not make sense to me for 2 reasons:

1. If the lens fitting is watertight, then the water should not drain out when I take the ensemble out of the tank and so I should be OK.

2. If the lens fitting is not watertight and the water does drain out, then the pressure of the sea water should force water back into the crevice between the lens and housing.

Any thoughts on this?


A couple of thoughts. First, attach a piece of fishing line to the lens and the housing. Then if you drop it no worries. Second, if the rinse tank is fresh water (and I hope it is) then the water film will be fresh and salt will try to move into the fresh water. This means schlieren will be seen and some not so nice pics. Take the lens off UW then put it back, getting rid of any air and any mismatch between the water on the lens and the water where you are diving.

Bill

Bill Van Antwerp Canon/Nauticam/Subal/Inon Lots of glass


Technical Advisor to Bluewater Photo


http://www.blueviews.net

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Postby James » Tue Mar 15, 2011 7:30 pm

First, I never put my camera in those so called rinse tanks and second the problem of trapped air is often a non-problem. Some mounts/lenses tend to trap an air bubble, others don't. In addition to an air bubble are tiny bubbles on the port lens or aft lens of the accessory lens, often simply gently shaking the rig will cause them to dissolve, sometimes the lens needs to be removed and the bubbles fanned off.

For the most part I rarely have bubble problems, mount my lens on the boat, jump in and take pictures and I never put my camera in a rinse bucket.

James
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Canon S90 with FIX90 housing, 2X Inon D2000 strobes, DIY tray, Inon UFL165AD, Inon UCL165AD, Inon UWL100-67 with dome kit, ordered Fisheye UWL-04
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Postby Hintermann » Sat Mar 19, 2011 11:13 am

Thank's people. I liked the fishing line idea and went out to a local tackle shop today and bought a small spool of 0.6mm micro-braid that easily fits around the lens groove and can be secured. I'll make a loop at the other end and secure it to the lanyard through a ring. The line has a breaking strain of 6.8Kg, far more than my lens' weight and in any case, will not have to take the strain in air.

The other end of the lanyard clips onto one of the convenient eyelets on the Iklelite strobe tray so that the lens ensemble can be safely detached at that end when I do not want to use it without having to fiddle with the secured braid.
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