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two stops to allow more light to reach the film/image sensor, compensating for the light absorbed
by the water. Note: In water, the visual distance to the subject is about 0.75 times the actual
measured distance.
Because proper Aperture Value / Guide Number may vary due to water conditions, strobe angle
and distance relative to subject, subject reflectivity, amount of magnification of lens and various
other factors, learn by taking test images, build up experience and adjust manual settings according
to the situation.
Also note that as the distance from camera lens to subject becomes shorter, the camera lens tends
to become "darker" and less light will reach the film/image sensor. Adjust settings accordingly.
Also, be aware that natural light may increasingly contribute to the exposure based on you settings,
so taking test images and analyzing the exposures is useful.
The chart below should be used as an initial reference guide for setting manual exposure, and
supported with actual testing and experience to obtain optimum images.
Distance
ft
m
1
0.3
2
0.6
3
0.9
4
1.2
6
1.8
8
2.5
How to interpret the exposure calculations
For example, when the film/image sensor ISO value is 100, and the distance to subject is 0.9
meters / 3 feet (underwater visual distance), at FULL flash, -2 flash and –4 flash settings, the
aperture settings would be either f/9, f/4.5 or f/2.2 respectively.
INON D-180 Manual
Version 1.
October 4, 2003
Copyright 2002, 2003 by INON America, Inc. All rights reserved.
ISO 100／Underwater Manual Exposure
Manual Setting Position
Full
18
13
9
6.3
4.5
3.2
-2
-3
9
6.3
6.3
4.5
4.5
3.2
3.2
2.2
2.2
45
-4
4.5
3.2
2.2
G.N.=18
ISO 100 x m
in air
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