Magnifying glass

[donnad]

hi there. I'm trying to find an underwater magnifying glass that can be attached to a lanyard. I would like a small oneocket size . And I want glass not plastic. And what about 'regular' magnifying glass? My understanding is that they don't work that well /that you need one made specifically for underwater use. Please let me know if you've found one that's not pricey that works well and is small. Thanks !!!!

 

[Lorenzoid]

I bought a "pricey" one, and it works great. Others who are handier than me have made their own, by sandwiching and sealing a lens between two transparent covers. The idea is that the lens is suspended in air, so that the index of refraction is maximized. The problem with simply looking through a lens, such as an ordinary magnifying glass, underwater is that the index of refraction between water and glass is less than the index of refraction between air and glass. So an ordinary magnifying glass won't magnify as much underwater as it does in the air. It magnifies--just not as much. Before I bought my pricey underwater magnifier, I used a cheapie ordinary one from Harbor Freight, and it was, let's say, adequate. But I wanted better.

 

[Lorenzoid]

Some previous threads:

magnifying glass

Underwater magnifier

Looking for a underwater magnifying glass

 

[fmerkel]

You want a cheap plastic one. Glass doesn't work well unless it's specially made (the refractive index thing mentioned), so expensive. The scratches in the plastic tend to disappear underwater, it's light, and you won't be so upset when you lose it......yes, you will lose it.

 

[donnad]

You want a cheap plastic one. Glass doesn't work well unless it's specially made (the refractive index thing mentioned), so expensive. The scratches in the plastic tend to disappear underwater, it's light, and you won't be so upset when you lose it......yes, you will lose it.

Does the plastic one work pretty well??

 

[fmerkel]

I had the REEF one, $50 back then, more than that now I'm sure. Worked well. Lost it. Small, hard to keep track of, especially if you pass it to other people to see small stuff and you are a tad narc'ed.

Got a small plastic one for like $2-3. Actually pretty impressed. Not much risk there, so try it out. You can upgrade if you are unsatisfied.
I've lost a couple of those also, but no big deal.

 

[tursiops]

You want a cheap plastic one. Glass doesn't work well unless it's specially made (the refractive index thing mentioned), so expensive. The scratches in the plastic tend to disappear underwater, it's light, and you won't be so upset when you lose it......yes, you will lose it.

This is backwards. The refractive index of plastic varies a lot, but really good plexiglass is 1.49, whereas a decent glass is 1.6 or higher. That means glass will function better as a magnifying glass, especially in water, which has a refractive index of 1.33. It is the ratio of the two rfactive indices that determines the light bending, thus the magnifying power. Compare 1.49/1.33 = 1.12 versus 1.6/1.33 = 1.20; glass works about better. The cheap Harbor Freight rectangular magnifying glass for just $2 works amazingly well, even though they rate it at only 4 power in air. You'd need a much stronger plastic magnifier to achieve the same magnification in water.

 

[fmerkel]

Dunno the specifics of the plastic one I got. It was from the Caribinn on Bonaire. It was small, cheap, and in terms of seeing stuff seemed to be about as effective as the REEF magnifier, though the REEF was larger and did have better optics. It hurt to lose a $50 magnifying glass though.
I've take run of the mill glass magnifiers down and found them to be pretty useless.

 

[Centrals]

DGX will sell you a gauge reading mask with selection of magnification X1, X2 or X3 for $50.00.
I am using it to read my gauge or slate(deco dive plan) rather than looking for pygmy sea horse. Perfect.
Not sure what it is made from.

 

[charlier]

My wife purchased a cheap glass magnifying gass in a plastic frame in a thrift store. She drilled a small hole in the handle for a lanyard. The magnifying glass probably costs less the $10, more like $5USD. She has used this magnifying glass for 100's + dives with any problems. I attached a marginal photo - you can see her hand surrounding the magnifying glass.