Red is wrong for night vision

by Peter Swanson, Loose Cannon
Ask an audience of cruisers to identify the optimal light for nighttime navigation, and most will answer that red is best. The question comes up from time to time in nautical Facebook discussions, and red is the answer endorsed overwhelmingly by commenters discussing how best to preserve “night vision.”

Night vision, otherwise known as “dark adaptation,” allows people to see better at night but this advantage can be lost in a flash when someone is exposed to bright light, even something as innocuous as opening the fridge door. It can take up to 40 minutes in darkness to regain one’s night vision. Conventional wisdom has long endorsed red light as a best practice to preserve it, hence the little red bulb in all those old compasses of ours.

Problem is: The answer is incorrect, always has been. “Rig for red,” as the Navy used to say, was never a best practice. It’s just that recreational boating followed the lead of the World War II military, which had actually misinterpreted the data. – Full report