50/50 Photography (continued)

The first problem stems from a mixed environment. Lenses which were designed to focus in one environment (air) must now also be able to focus through water.

The second problem is that water absorbs light much readily than air. As a consequence, there is less light below the water than there is above --the photographer can either expose for a subject above the water, or below, but not both. So how does the photographer get around these limitations?

In the first case, the best way is by utilizing a split-diopter accessory lens. A split-diopter lens is merely a screw-on filter that fits over the primary lens. Split diopters are essentially photo-quality magnifying lenses cut in half and mounted in a rotating bezel. (most camera retailers either carry or can order a split diopter from a distributor).