useless nerdy facts of the day

[billvon 3,107]

Your eyes are remarkably non-linear; they respond to light in very odd ways. There are two basic kinds of cells in your retina - rods and cones. Cones can detect color, rods black and white. Cones need a lot of light, rods need very little. Thus rods give you night vision and cones give you daytime color vision.

Also, the center of your vision (the fovea) is almost all cones, with more red-sensitive cones than average. Outside your fovea, rods start to dominate.

Many people think that red light "saves your night vision." It really doesn't, not any more than any other color. What it does do is allow the fovea to work with lower light levels, which is important if you want to read detail at night (like, say, a map.) If you don't care about detail - you just want to walk around without hitting anything, for example - green light is actually a lot better, and preserves your night vision more effectively. Why? Because your rods are most sensitive to that color, and you will need very, very little of it to see in all areas of your eye except dead center. You'll have a blind spot in the center, but you'll be able to see over a very wide angle.

The term for visual acuity in bright conditions is photopic; in low conditions it's scotopic. Intermediate brightness levels are called mesopic. Each 'mode' of your eye has different peak sensitivities. The ubiquitous low pressure sodium lamp (i.e. those yellow streetlamps) comes close to your photopic sensitivity band, so they're very efficient at higher light levels. They're not so good at lower light levels. Which means that they provide great illumination near the source but really poor illumination farther away from it. A green streetlamp would provide better illumination at longer distances, and so might be a better choice if you wanted to get the maximum efficiency from your streetlights.

[wildblue 7]

Quote

A green streetlamp would provide better illumination at longer distances, and so might be a better choice if you wanted to get the maximum efficiency from your streetlights.

Not to mention would give your neighborhood a cool, creepy feeling.

it's like incest - you're substituting convenience for quality

[Deuce 1]

Bill, that is why the chicks dig you.

Fovea.

[Shotgun 1]

It's a good thing for you that being a nerd is sexy nowadays.


(Well, not that you have any reason to care... since you already have a hot wife and all...)

[nanook 1]

What's cool about all this is at night, you can see that darker area in the center of your vision. If you scan back and forth using your perihipreal vision, you can see better than most.

_____________________________

"The trouble with quotes on the internet is that you can never know if they are genuine" - Abraham Lincoln

[outlawphx 1]

I suppose that's why the view from night vision goggles are green. It probably has the least impact on your vision when you take them off.

[billvon 3,107]

>I suppose that's why the view from night vision goggles are green.

Actually, that's an artifact of the phosphor in the NVG system. But it does work out well, since we're most sensitive to that color at low intensity levels.

[lawrocket 3]

So would a black light be the best light for seeing in the dark?

My wife is hotter than your wife.

[rehmwa 2]

Quote

So would a black light be the best light for seeing in the dark?

that would be a Miller Lite

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[PLFXpert 0]

Quote

Because your rods are most sensitive to that color

All this talk about rods and cones....I think I need to start wearing more green for my boy-toy

Paint me in a corner, but my color comes back.