Science: How to See in the Dark

In two darkened rooms in the basement of Yale’s Institute of Human Relations, a Yale psychologist is working on a prime problem in wartime human relations: how to see at night. Last week tall, affable Professor Walter Richard Miles reported that he was beginning to get somewhere. He had developed a pair of goggles to help Navy lookouts and plane spotters. Fresh from a three-month study of blacked-out London’s darkness, he also had some helpful hints for civilians on how to get along when the lights go out.

A longtime student of night vision, Professor Miles explained that the retina of the eye has two kinds of vision cells cones and rods. The cones (about 7,000,000), concentrated in the retina’s center, are used mainly for day vision. The rods’ (130,000,000), distributed around the edges, are used for seeing in the dark.

“Within five or six minutes after we enter a well-darkened room,” says Professor Miles, “the cones … by means of a chemical process, become ten times as sensitive. This is as far as they can go. But . . . the rods get more and more sensitive for 20 or 25 minutes after the cones have stopped adjusting, finally [increase their sensitivity] 1,000 times. This is night vision.”

Dr. Miles’s new owl-sight goggles are designed to eliminate this period of waiting for the eyes to get used to darkness. Having found that the rods work better in red light, he made his goggles of red filters. A lookout who wears them for 30 minutes before going on duty can see almost instantly when he steps into darkness.

Because the rods are on the periphery of the retina, the best way to see an object at night is not to look directly at it but at a point near it. The catch in this off-center technique is that it handicaps a person in judging his distance from an object; pedestrians sometimes walk smack into a truck at the curb because they suppose that the dark mass they see is a building across the street. Dr. Miles offers a tip on how to judge distance at night: the nearer an object is, the fuzzier its outlines are; move the head from side to side—the object will seem to move rapidly if it is close by, slowly if far

Another tip: a pedestrian in a blackout should keep out of the way of a vehicle with lights—he can see much better than the driver.