pcray1231 wrote:
As far as colors, I always liked gray, looks more natural. The yellows and ambers look brighter in the daytime and some like that, and it makes you think they'd actually improve vision at dusk. But once dusk comes, they don't. All sunglasses are designed to block some light, so there's no such thing as a pair that will improve vision at low lights.
Not quite true.
What they do accomplish is cutting back MORE blue light than the other spectrums, which in turn improves contrast allowing you, in theory, to see more detail and better.
You are also correct that they will reduce the total amount of light returning to your eyes, so its a trade-off but in the transisitional hours, you can unequivicably get better contrast through the use of minus blue glass.
Now, this is the best example I can find, but its a bit more extreme, a Wratten #25A red filter.
By cutting back blue light, you increase the contrast available (in that case film, in our case the eyes). It is absolutely contrast enhancment, and thus why people think they can see better with yellow or amber lenses. Cuts teh blue light, which is exactly what you need in the waxing and waning hours of daylight, in haze, or overcast days.
Edit: Grey lenses are more neutral, they should not affect overall tone, just the amount of light that filters in. To go back to photography, "neutral density" filters (wratten 96) are always grey, and have no effect on tone for that reason.
