Are standard camera glass/UV filters waterproof?

[DazedAndConfuzed]

Hi,

I am wondering if the regular UV filters are waterproof? I do notice some that indicates it is waterproof, but only in the sense water will bead right off. I am inquiring because I have an old an above water 52mm +3 diopter from my SLR sitting there unused, and I asked whether I can use it underwater earlier and was told about the drop in effectiveness (someone mentioned a 3 diopter loss (+4 becomes +1), I think it is a 75% loss, so +3 becomes +0.75).

So what I was thinking was to screw on a 52mm UV or glass filter in front and behind the diopter lens, thus allowing it to have its full +3 diopter capability (should be like a +9 wet lens), sealing the threads to make it waterproof. I am just wondering if those UV filters are sealed enough so that water would not seep between the outer ring and glass into the airspace I have created. Plus, would those std glass be able to stand the pressure of a std OW dive of up to 5ATM? That would be like putting a 190LB of weight on the glass len's surface.

 

[smellzlikefish]

I have to ask for what you are using this setup?

 

[DazedAndConfuzed]

I have a camera with a min focus of around 8" in max zoom (21mm (105mm in 35mm equiv)). It has a super macro option which allows me to focus down to 1" or so, but the lens gets fixed at 10mm (50mm in 35mm equiv) and frequently I have to get real close to the subject, which becomes an issue with strobe lighting and scaring the critters away.

If I just use the existing +3 diopter underwater, its refractive power due to the water/lens transition of light would be cut to 1/4 or so. A +3 diopter would be effectively become a +0.75 diopter, and my camera's min focus would only go from +5 (add +0.75) to +5.75, which would be 6.85", giving it a 17% increase in the subject's size.

But if I encapsulate the +3 diopter between 2 flat plane pieces of glass like UV filter, then the lens to its adjacent medium (which would be air now) would still have its full refractive power, thus it will retain its full +3 diopter rating, and my camera's min focus would go from +5 (add +3) to +8, which would be 5", giving a 60% increase in subject size.

It is similar to the concept of the Subsee closeup lens http://reefphoto.com/shop/index.php?main_page=product_info&products_id=4444

I can also do it with above water +4 or +5 single lens diopter, which are pretty cheap compared to the wet lens, it would allow me to get even closer.

 

[flareside]

As to whether the UV glass will withstand the pressure is a function of the thickness and quality of the glass. There is no way to say if the specific ones you have are adequate. I have had success with this but I was intentionally using thick, hardened glass.

As to whether the edge of the glass is sealed against the frame, the answer is no. If your filters allow removal from the frames, a thin silicone glue between the glass and the frame works great. Same goes for the threads. If your filter glass is press fit into the frame, applying the glue to surface on the soon to be wet side might work but likely won't last.

Why not just pick up a cheap +10 off ebay and be done with it?

 

[bvanant]

Well there are no cheap +10 on ebay that are +10 in the water I think is the point.
Bill

 

[flareside]

No but if his calculations are correct, it becomes a +2.5 with a much greater chance of success than the +3 assembly he is working toward. If the $5 +10 isn't good enough, he can get a +20 for $9.

 

[Nemrod]

No, they are not water tight. I used to keep a Skylight 1A on my Nikonos III. It immediately floods upon immersion.

N

 

[bvanant]

I think the better answer is to get a proper wet lens for $150 or so and stop buying Starbucks coffee for a week.
Bill

 

[DazedAndConfuzed]

No but if his calculations are correct, it becomes a +2.5 with a much greater chance of success than the +3 assembly he is working toward. If the $5 +10 isn't good enough, he can get a +20 for $9.

LOL, a +10 would either be +2.5 or +3.3, depending on which formula is right. I thought about that. And why does companies like Inon or others make dual element +6 units? Underwater, they become +2, which hardly need any optical corrections at all. Plus once it is a dual element, they have to worry about making it waterproof.

Anyway, I was thinking of doing it to see if it would actually work.

 

[Larry C]

No. The underwater +6 is a +6 because it has airspace and dual lenses. The wet single lens is surrounded by water, which has it's own natural refraction negating the effect of the lens. The underwater lens is also designed to be watertight, is coated to prevent salt corrosion and uses a fitting that is generally anodized as well to prevent salt corrosion. My Subsee +10 is about 2" long and quite heavy to prevent it imploding under the pressure of 3-4 atmospheres at 60-100 feet or more.