Color at Sea

Estimating distance and preserving night vision
It’s a little-known fact that some colors appear closer than others at sea in daylight. For instance, if you’re trying to judge your distance from an object, red colors generally appear closer than blue and green colors. So you may not be as near to that red buoy as you think.Even more fascinating is the fact that this effect is reversed at twilight. As your eyes become accustomed to growing darkness, they are more sensitive to blue light than to red, so blue seems to be closer. And, as night falls, red objects grow correspondingly dimmer and blacker. That’s also why chart lights and compass lights are red—they don’t destroy your night vision as white lights do.If you’re on watch in the cockpit at night and have to go down below temporarily into a lighted cabin, there are two good ways to preserve your night vision. The first is to put on a pair of red ski goggles, which filter out all except red light. The second is to keep one eye tightly closed—or to slip an eye patch over it. In the latter case, you’ll only be preserving your night vision in one eye, but considering that it takes up to 20 minutes to regain full night vision, you’ll be a lot better off with one good eye than with none.See also Nighttime Boating.