Photography is a challenging past time and requires a lot of detailed research when being pursued. The difference in the refractive indices of water and air and the density of water determine the color and quality of the image being taken. Many a times, a photographer captures a colorful and bright image underwater but is disappointed by the resultant effect. Underwater environment is monochromatic and produces a blue or green haze effect on the images, depending upon the location. This happens because of water that filters red light. The extent of filtration of the red spectrum increases with increase in depth of diving.
Water acts as a light filter and results in blue-green photographs when taken at depths of more than 5 feet. This however deteriorates further and results in grey or blue-green images at depths of about 50 feet. Colors disappear as light travels through water, red being lost at 5 meters depth, and only blue and green remain beyond 10 meters. This setback of color loss is corrected by the use of color correcting filters. The utilization of a red filter finds commonplace while filtering out the blue spectrum of the ambient light. The use of flash or light also finds application in the color correction. The color correcting filters provide scope for capturing chromatically correct pictures at depths of up to 50 feet or more, without flash or artificial light sources. The filter also prevents the deterioration or change in optical properties with time.
The color correcting filters change the color balance as they selectively allow some colors to pass through. The types of filters vary for use in green temperate waters, blue tropical waters and at different depths. The filters can either be mounted on the camera housing’s port or attached to the camera lens. However, filters give better results when attached to the camera lens (front or rear). While using these filters, the photographers need to look into certain matters like:
- The subject should be beyond 8 feet deep in water.
- The surrounding water should be cyan colored (both fresh and sea water).
- The subject and camera should be positioned such that the daylight travels a distance of 8 to 50 feet through the water.
- An imbalance of water pressure on the outside of filter should be avoided by flooding the space between lens and filter to prevent damage to the filter or camera.
- Filter flooding is however not required for underwater cameras with housings.
- Avoid use of filters above a depth of 5 meters (15 ft) as there is a presence of enough light.
- Avoid taking pictures with flash or artificial light when using filters, as this will yield overtly orange photographs.
White Balance (WB) on the camera can be used for the automatic color balancing by setting the camera to a predefined condition suitable for differing conditions and light sources. The color correcting filters reduce the amount of light reaching the camera and therefore result in dark or blurred images at greater depths. The use of strobe or dive light is advisable at depths below 10 meters for better results.