What's the difference between the 580 and...
What's the difference between the 580 and the 400 lens? Not just the 580 is better - how/why is it better?
They are both good lenses, with polarization and 100% UV protection. The 580 in 580 lens refers to yellow bands of light. The 580 lens (their premium lens) is supposed to block more of the yellow shades (which they claim the eye has a hard time processing). This is especially important if you are tying to see better on water (like when sightfishing or sailing). The 580 is a glass lens that comes in gray, copper, blue and green mirrors. The Costa Del Mar website describes the recommended uses for each color. http://www.costadelmar.com/SeeOutThere/Technology/PureLensPerfection/
FWIW, I have two pairs of shades with the 580 lens and find that they are excellent for sightfishing and general use (although Kaenon sunglasses would be a close second).
The reason the Costa 580 lens is better than the Costa 400 is that we have found on the light spectrum scale, the human eye cannot see yellow light. That is the light that causes glare and distortion. So when you can't see the glare or the distortion everything you see is more vivid, more real. Your reds are redder, greens are greener and blues are bluer. It doesn't change what you are seeing, it helps you see what is truly out there.It is a patented lens and the Costa 580 lens comes in (5) colors, Gray, Copper, Blue Mirror, Green Mirror and Silver Mirror.
The Costa 400 is still the bar that all high quality polarized sunglass companies compare themselves to, Costa just took it up a couple of notches.