With the increase in water depth, colors of the visible light are subject to gradual absorption. The red-parts are first to disappear, followed by yellow, green and blue. After reaching a depth of approximately 60 meters (197 feet) all colors are gone and the diver is surrounded by darkness. In situations like this, including night- and cave dives, it is essential to make use of a dive light. The diving experience is not only affected by luminance intensity and luminous flux, but also by additional factors such as light distribution and color temperature.
So, which color temperature should my dive light produce then in order to enable optimal vision under water but at the same time also provide an authentic representation of the underwater environment?
In our first part of the series: “How does water affect the properties of light?”, we explained the basics of light absorption and the properties of the light spectrum under water.
Due to a greater efficiency, most dive lights are equipped with powerful LED lamps, which produce different light colors and therefore different ambiences depending on their respective color temperatures (measured in Kelvin).
Light appears to be more yellow and warmer at a lower color temperature, and bluer and colder at higher color temperatures. In comparison: a candlelight produces a warm light, with approximately 1.500 Kelvin. A light bulb with 2.700 Kelvin is still perceived as “warm white”.The sunlight’s color temperature ranges from 5.000 K to 5.500 K, but may shift up to a value of 7.000 K during cloudy skies.
Light with a color temperature between 3.300 and 5.300 Kelvin is commonly referred to as “neutral white” light. The following graphic illustrates the color temperature in Kelvin.
Color temperature of dive lights
The light spectrum of LED-lamps covers the range from 2.7000 to 8.000 Kelvin. LED-lamps are not able to represent the color spectrum evenly, this results in weaker reds. The following applies: the higher the color temperature, in other words the cooler the light color, the worse the representation of the red color. The color temperature of diving lights is usually between 5.000 and 7.000 Kelvin. Since there are less red-parts, which are absorbed earlier, a higher color temperature allows for a slight increase in illumination distance. On the other hand, a lamp with a lower color temperature and therefore more red parts might represent more “natural” results.
The following graphic depicts the characteristics of the color spectrum of various LED’s as a function of the color temperature. Depending on the color temperature, certain colors or wavelengths, appear to be stronger or weaker. An overview of which wavelength corresponds to which color can be found [here]. A color temperature of 3.000 Kelvin for example conveys the red color better but is lacking in blue colors, whereas a color temperature of 5.000 Kelvin may be perceived as neutral.
All in all the ideal color temperature of a dive light depends on its application and the personal taste of the diver. Our experience has shown that 5.000 Kelvin is the best choice for most divers, since its very similar to the appearance of sunlight and is hence perceived as most pleasing. Especially during long diving sessions, the psychological effects of the color temperature should not be underestimated. In addition to that, most camera flash systems in photography are utilizing the same 5.000K, which allows for simultaneity use of both light sources.