Costa del Mar question--blue halo/artifact

[Wildfish]

Hi all,
I recently got a good deal on a pair of costas with the 580G mirror blue lenses. I needed a new bright sun lens, and these fit the bill.

The lens is super clear, colors are brighter, and contrast more pronounced than my other lenses. My only complaint is that when looking at a very bright sun reflection I see a slight blue dot or halo. It happens when there's some very bright glare reflecting off of the edge of a car, and faint blue dot is like an artifact made by the mirror on the front of the lens.

Small complaint, but they're pricey and should have no glare. So...anyone experience this? If it's a defect from laying a layer on the lens I can send them back. But I don't want to--I just got them and want to keep playing with them

 

[pcray1231]

I can't tell if your seeing the same as I see out of mine. Mine are the green mirror with the amber lens underneath.

But I have noticed something similar to what you're saying. It's a polarization effect, I think. The polarization is really tight in mine. If you think of light in various orientations, this particular polarization cancels out only a small portion of that spectrum.

A way to test this is, with ANY polarized lens, when you look at a glare reflection (such as off of a car window), hold the glasses at arms length and turn them horizontal to vertical. The reflection appears and disappears as you turn the lens. With the Costa's, the "disappear" effect is both more magnified, and over a shorter distance. i.e. that glare completely goes away but only at a specific orientation. Vary even a little and it's back in full force. With cheaper glasses, it merely minimizes that glare but does so at a wider range of orientations.

Now, the halo. Reflected light is, in theory, 100% polarized, meaning all at the same orientation. But theory does not perfectly match reality. There are imperfections in that surface which cause some of the reflected light to be at a slightly different orientation. So, while the Costa's 100% remove the glare at the orientation it's supposed to be at, those light rays at other orientations are not filtered, whereas many glasses would tone those down too.

On a solid surface the result is a faint, ghost like halo where there would otherwise be glare. On the water, the result is weirder. No glasses at all = all glare. Cheapo glasses = glare reduced everywhere, not eliminated anywhere, so you see in the water better and it still looks like a consistent surface. Costa = glare 100% eliminated on flat water, but hardly reduced at all on the sides of steeper ripples. Glimmering effect. In the end, I can see stuff better in the water. But the weird glimmers take some getting used to.

This is my first pair of glass lenses in sunglasses, and only pair of costa's. If I had to guess, it likely has more to do with the method of polarization in glass vs. plastic. Hence, not costa vs. others, but glass vs. plastic. Costa plastics may be different, and glass versions of other manufacturers may be the same.

 

[Wildfish]

Thoughtful response--thanks pcray. These are also my first glass-lens sunglasses, so perhaps you are right. The effect does not happen with my polycarb maui's. On the other hand, the maui's do not have as much mirroring, which I thought might be the culprit.

Again, I appreciate the thoughts. Interesting note about the tightness of the polarization. That hadn't really occurred to me. I'm still a little skeptical this is the cause, since the halo is definitely blue, and the polarization is in the grey lens (in other words, I wouldn't expect the glare to come in blue but rather uncolored). In any case, it's really a small issue. But I do appreciate the thoughts.

 

[pcray1231]

Perhaps your halo is not the same as mine, or has a different reason.

I still say it likely has something to do with the polarization, not mirrors. I'll offer another hypothesis:

With the way polarization works, lights of different color (different wavelengths) may be filtered out differently. Blue light is all the way at the short end of the wavelength spectrum, and thus least likely to be caught by polarization. If the orientation of the light coming in is near that "boundary" orientation where it will be filtered, only the blue glare will get through, and the reds and oranges won't. If this were the case, the halo should appear and dissapear as you change your angle on the glare surface.

A 3rd point. The wavelength of blue light is nearing the wavelength of UV light. Which is supposed to be completely blocked by a separate filter (not polarization). Maybe what you're seeing as a halo is actually attenuated UV light which gets it out of the UV range. In this case it likely would not change with angles.

Or maybe you have an issue. Scratches, dirt, and a poor grind can halo things.

Have you had them on the water yet? I think you'll see the "ripple" effect I'm talking about.

 

[Wildfish]

Not yet--just got them a few days ago. I'll definitely give them a try out on the water (maybe even book a striper trip soon)

Thanks!

 

[Gone_Phishin]

Pcray'd

Is there anything this guy doesn't know about?

 

[JackM]

Gone_Phishin wrote:
Pcray'd

Is there anything this guy doesn't know about?

Transubstantiation.