Underwater illumination ¹⁾

Lighting and color conditions are drastically different for underwater shots. Whereas in the atmosphere, a difference is only noticed where large changes in altitude occur, color under water undergoes such violent changes after onlya few meters that films can be affected. Picture 1serve to indicate how lighting conditions change at increasing depths.

 

 

 

 

 

 

 

 

 

 

Picture 1: Transmission of water

Looking at the columns of figures in the table, it is easy to see that each film (manufactured for use in the atmosphere) receives too great a proportion of blue light, so that color film has a blue color cast and black-and-white film is incorrectly rendered. Even in clear water at a depth of more than 10 m (33 ft.), color film reproduces red as anything between brown and black, ut other colors, too, are falsified. The table shows how correct color reproduction can be achieved with color film using filters. The use of infrared film under water is practically impossible since water absorbs all heat radiation. In black-and-white photography, a high level of sensitivity in the blue-green-yellow range is essential. A highlevel of red sensitivity results in a highlevel of overall sensitivity which cannot be fully exploited in water. If artificial light is used in deep waters, daylightfilm can be retained since water hast he effect of a compensating filter. With a light path of 4-6 m (13-25 ft.), photo-flood light produces reasonable quality on daylight film.

Table 1: Lighting conditions change change at increasing depths

To sum up, it can be said that the use of filters under water also result in a considerable improvement in reproduction although the very fine grading possible in light-air conditions is hardly practical.