This is a Guest Post by Mike Ketcham
Seems pretty straightforward. What’s not so obvious is why colors drastically change underwater, even in relatively bright environments. Even more strange, colors selectively change at different depths. So what’s going on, and why would a dive light help when there is enough light to see clearly?
Let’s take the way-back machine back in time to high school science class. Don’t worry, we won’t stay long. Do you remember the experiment where visible light was separated into a rainbow (or spectrum) of colors with a prism? If your science teacher was really good, they used a second prism to recombine the rainbow and form a visible white light beam again.
The natural light we see from the sun is actually a blend of a number of different colors. Your teacher may have covered ROY-G-BIV, the acronym for the seven conventional colors of the light spectrum (Red, Orange, Yellow, Green, Blue, Indigo and Violet). An object’s color is determined by the color of the light spectrum the object reflects to our eyes. A red fish appears red because it reflects the red light band to our eyes (and absorbs all the other color bands). Check out Wikipedia’s entry on color if you’d like to read even more science on this topic.
Enough of high school. Now we’re back to present day and the question of why different colors disappear at different depths. It happens because water absorbs some parts of the color spectrum faster than others. As you descend from the surface, red is the first to go. A red object will appear blackish-green because light from the red color band is gone. Since light from the other members of the color spectrum is still present at this shallow depth, the other colors appear as their natural color. As we descend deeper, the other color bands are filtered out sequentially – first orange, then yellow, then green and blue. The result is an underwater world that is devoid of its true color.
This is where dive light magic enters the conversation. Dive lights are not just for diving in dark places. Under water, the beam from a dive light replaces missing color bands and helps restore the color spectrum. The brilliant colors of the tropical world are revealed, and the beauty of the sea appears. Like with sunlight, water will adsorb your dive light beam over distance. So the brighter your dive light is, and the closer you are to your subject, the more natural and realistic colors will appear to be.
If you haven’t looked at dive lights lately, you’ll be amazed at how much they’ve improved. The new breed of LED dive lights are a giant step forward from incandescent (halogen/xenon) and HID dive lights. Relative to their predecessors, LED dive lights have exceptional battery life, superior durability and extended lamp life. So bring a dive light along on your next dive, and see the wonderful world you’ve been missing.
To read more about dive lights and related scuba stuff, add Dive Lights Direct to your Google+ circles.
Original Image Source: NOAA
Additional Image Modification: Dive Lights Direct