Dive Lights – Are They Only for Seeing in the Dark?
Dive lights are necessary for scuba diving in dark environments like the ocean at night. If you don’t have enough light to see clearly underwater, it’s not much fun, and it can get dangerous pretty quickly. Pretty obvious right? Dive lights have another purpose though, and its one that many people don’t think about.
When scuba divers become certified, they’re exposed to a ton of information in a short amount of time. Let’s face it, it all moves quickly and most people are focused on diving safely and becoming familiar with their equipment. The interesting background information doesn’t always stay top-of-mind. One of the topics that is easy to forget is the concept of how water selectively absorbs and removes the color bands of the visible light spectrum with distance and depth.
Natural light is actually composed of a mix of different colors like red, orange, yellow, green and blue. An object’s color is determined by the specific color band that an object reflects to the human eye. For example, a red flower above water looks red because the flower reflects red light rays back to the eye (it does not reflect the non-red colors).
Colors work a bit differently under water. As sunlight descends from the water surface, the different colors that compose sunlight are absorbed by the water, and they disappear at different depths. Red is the first to be removed, then orange, yellow, green and blue in that order. At about 15 feet below the water surface, all the red colored light has been removed from the original sunlight (but most of the other color bands remain). As a result, a red flower no longer appears as its vibrant natural color – it appears more drab and grey.
The beam of a dive light restores the color spectrum and allows a diver to see the ocean’s real colors. Red corals appears as their natural red color because the red color band is present and is reflected to the human eye. Keep in mind that over distance, water will absorb the color bands from the beam of a dive light just like it does with sunlight. So even with a dive light, the greater the distance you are from an underwater object, the less natural its color will appear.
So the next time you’re diving, take a diving light along and observe the color differences at different depths with and without the light on. You’ll be surprised at what you see.