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The Private, Exclusive Guide for Serious Divers Since 1975
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August 2018    Download the Entire Issue (PDF) Available to the Public Vol. 44, No. 8   RSS Feed for Undercurrent Issues
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Not All Magnifying Glasses Will Spot Critters

from the August, 2018 issue of Undercurrent   Subscribe Now

You've seen all the big fish, so for your next dive trips, you want to focus on macro and super-macro marine life . But to enjoy the very colorful but typically tiny creatures that your dive guide will search out and point to, you may need the help of a magnifying glass .

Light is refracted when it passes from a dense medium (the water) to a less dense medium (the air in your mask), making things look larger or closer . But when light passes from a less dense medium (the water) through a more dense medium (the glass in a magnifying glass), the opposite happens, counteracting the effect of the convex lens' curved surface .

The result: A magnifying glass is apparently less effective in water than it is in air . Which means, to see macro life, a good one will have to have at least a 10x magnification in air . Taking that magnifying glass you use to read any fine print (which probably has a magnification ratio of around 4x) will only lead to disappointment.

If you want something conventional with a handle, Amazon has a few inexpensive products in the 10x magnification category . Avoid anything with a built-in light (many of the more powerful glasses come with this feature) . One we like is the Insten 10x Handheld Magnifying Glass with Handle, available for $8 (

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