A part of the problem of their difficulty in evaluating what the best color of light is that they didn't have any colored lights! All they had was incandescent lighting, which is uniformly......white! The best approximation they could come up with to give colored light was filters. If you'll look at Gino's photo, which I wish he had posted instead of only linked to, you'll see that the light has a very strong yellow component in it. Actually, I suspect that is more white than yellow and the color balance of the shot is wrong.
The upshot is that filtered light typically, and here specifically, is nowhere near a pure red light. Therefore they had to have significantly dimmer red light to minimize the white contamination that leaks through their filter.
To illustrate, Sky and Telescope magazine has a logo with white lettering on a red background. Find something similar and go into a closet with a flashlight with a red filter and a red LED flashlight. The red LED flashlight emits actual pure red light. Flip on your red filtered flashlight and read the white lettering. No problem. It's clearly visible. Why? It's because your light isn't red.
Now try it with the red LED flashlight. Shazzam!!! You can't see anything but a red rectangle. Why? Because white results from reflecting all colors of light striking it. Well, only red strikes the white lettering, so what color do you see? Red. Red against Red is no contrast and the lettering is invisible if your red light is pure.
If the submarines had pure red light available there would have been no reason to run those puppies at 1/5 normal brightness. They would have been less visible, more dark adapted with more comfortable light levels.
Irrelevant aside: What color is the moon? What color do you see? In actuality, the moon is a very, very dark gray, almost the same color as a briquette of charcoal. It seems to have some subtle brown shades in parts of it, but they really can't be detected without serious image enhancement. So why does it look white to us? Because we don't see with our eyes, we see with our brains. In this case, the brain sees the background sky for what it is: completely black. There is some light coming from the moon. It has no color (well, maybe that subtle brown undertone. Give me a break!) and is millions of times brighter than the background. The brain paints it white. That's called imputed color, mentally constructed from the contrast with its surroundings.
|