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measured, the distance scale should be set at 3/4 the measured
distance to compensate. For example, to focus the lens on an
object 10 feet (3m) away, set the distance scale to 10 x 3/4 or 7.5
feet (2.2m).
Exposure
For accurate exposures underwater, an exposure meter in a
watertight case is recommended. If a meter is unavailable,
however, the following procedure will generally give satisfactory
results: first measure the light above water. Use this exposure
setting for depths up to three feet(lm) and open up the lens one
full stop for each additional three feet.
Whenever possible, avoid pointing the camera straight down.
Since the light source is behind the camera, illumination is flat
and contrast is poor. For best picture quality, try to shoot
horizontally.
Asdepthincreases, light falls off rapidly. Therefore flash may be
necessary at depths of 20 feet (6m) or more, espe cially with
color films.To compensate forlightloss underwater,daylightguide
numbers for flashunits mustbeadjusted according to experience.
Some experimentation will usually yield the correct adjustment
for a particular unit.
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