Knowing the Lenses for Underwater Photography

Aside from the other conditions which affect underwater photography, the fact that air is about 1,000 times as transparent as water creates a condition which makes it impossible to use standard focus lenses or telephoto lenses in underwater photography. To obtain contrast, the photographer must, as we have noted, get as close to the subject as possible. Also, while in surface photography it is possible to set the range for the distance from the lens to the subject, this becomes almost impossible under water. In almost all underwater picture taking, both the photographer and the subject are in motion, in three dimensions in a fluid medium. For this reason, the depth of field should be great enough to compensate for the inability to pinpoint the shooting distance with any accuracy. In surface photography such a condition could be corrected to some extent by reducing the diaphragm opening, but underwater photography needs every bit of light available, whether natural or artificial light is used. Therefore it is essential that the shortest possible focal length lens be used.

In addition, the wider the angle of field, the better the photograph taken under water. Unless the subject is framed against the ocean bottom, coral, or some other underwater object, the resulting picture will lack the frame of reference that makes a good underwater shot.

Many camera housings for underwater photography use a flat window or porthole through which the photograph is taken. This flat surface in front of the lens may cause some distortion outside the central portion of the photograph. This can be corrected by the use of a submarine lens attachment which is mounted into the front of the housing, replacing the flat window. This housing consists of two elements 3 or 4 centimeters apart, with the front surface in contact with the water. This correction lens permits focusing for the real distance of the subject without correction, and considerably increases the depth of field.

For lens use underwater there are two vital considerations and they are of equal importance: the power of the lens and its greatest aperture. About the minimum lens quality for underwater use is 1:3.5 for black and white or color.

The 35 mm still cameras are the most popular for underwater use, and the lenses that have proved most effective with them are 30 mm maximum for 24 x 24 mm and not more than 35 mm wide-angle lenses for 24 x 36 mm. For use in 16 mm motion-picture cameras, wide-angle lenses 12.5 to 9 mm focal length have worked out best.

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