The same color lense in the 400 is not darker (where darker is less light transmission). I believe that Costa's specs show the two types to be equal in percent of light transmission. (They will tell you if you don't find it on the website.) What is probably happening is that the contrast increase with 580G tricks the user into thinking more light was allowed in, when in fact that is not happening. For either technology, blue mirror and Green mirror are 10% transmission of light level! Silver mirror is a whopping 12%. They blocks THAT much - your pupil just dilates to compensate to some extent. It's interesting that we can see so well with so much light blocked.
Edited by Flippin-Out (05/24/16 01:32 AM)