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.

 

 

ISO 100／Underwater Manual Exposure
Distance

 

 

Manual Setting Position

ft

m

Full

 

-2

-3

-4

1

 

0.3

18

 

9

6.3

4.5

2

 

0.6

13

 

6.3

4.5

3.2

3

 

0.9

9

 

4.5

3.2

2.2

4

 

1.2

6.3

 

3.2

2.2

G.N.=18

6

 

1.8

4.5

 

2.2

 

ISO 100 x m

8

 

2.5

3.2

 

 

 

in air

 

 

 

 

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

45

Version 1. October 4, 2003

 

Copyright 2002, 2003 by INON America, Inc.

All rights reserved.