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Photographer's Note

Thought I'd try posting something a bit more unusual. This is actually a technically difficult shot to take for the following reasons:

(1) In order to achieve the split effect it is necessary to attach a large dome port to the underwater housing. Otherwise the water simply washes over the lens and it is difficult to place the horizon.

(2) Due to the optical effects of a dome port on an underwater housing, the focal point for the same distance is different above water to that below water. Hence trying to get both parts of the photograph in focus is extremely difficult. In this instance I have used a fisheye lens which has a massive amount of depth of field. This helps achieve focus in both parts. Divers using lenses with less depth of field use a split diopter on the lens to change the focal point below water (though this takes careful placing to put it on the water interface.

(3) because light is absorbed by water, the photo needs more exposure underwater than the above water part. In this case I've got around the problem by photographing in very shallow water and using an underwater flash to give a bit more exposure to the starfish.

I'm reasonably happy with the result. The photo was taken in the mangroves of North Sound in the Cayman Islands.

mbasil, tatadalou, padeg, rewshearer, leiju, broglia, iGirl has marked this note useful

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