I have always put Arc on the back side of sunglasses. Is there a reason why both sides are not coated.????
I have always put Arc on the back side of sunglasses. Is there a reason why both sides are not coated.????
AR gets very smudgy and looks bad on the front of a dark lens. The only time I've ever done it has been with Alizé. AR on the front can also look kind of like a mirror, so I'd rather put an actual mirror coating on the front and AR on the back.
Anti-Reflective Coatings are used for light transmission through the lens. Why would you put A/R on the front surface of a polarized lens when you are trying to reduce the light transmission to the eye? Just food for thought.
Ben
Adding to OpticianMS,
Putting an AR coating on the backside of the lens helps with internal reflections caused by the lens.
A Backside AR also helps in reducing unwanted reflections on the backside of the lens by allowing light that hits the backside of the lens not to be reflected back into the eye but transmitted through the lens.
A proper fitted frame will solve some of that issue too.
How does the fitting of a lens in a frame relate to back lens surface reflection reduction?Originally Posted by ShuString
The other comments properly explain backside AR.
I think ShuString is talking about a proper wrap which reduces unwated backside glare by not allowing light to enter through the backside of the lens.
Wraps increase base curve which in turn increase reflection- Simple solution, use backside AR, try Crizal Sun, it's backside Alize with a front side TD2 and hydrophobic topcoat, a good combo. Front mirrors can be an option as well.
Only 12% of all suns sold have an AR solution, seems like a nice opportunity the dispenser.
I haven't found frontside AR to be a liability, at least in polarized lenses. Mine have both sides covered and they don't look smudgy or weird or too bright.
DragonlensmanWV N.A.O.L.
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If you do the simple math, you find that when you increase the front curve, the back surface curve changes accordingly resulting in less than optimal optics. Remember that when making a lens, we are trying to match the curve of the cornea. Changing the curvature, whether flatter or steeper causes the natural abberations inherent in any lens to be more pronounced. Adding AR will help lessen these effects in any case. I have always been bugged by the back surface reflections in sunglesses, mainly seeing the side of my face reflected.
As to back surface only versus both sides, my opinion is that it doesn't make much difference except if a mirror is on the front. Some may say that AR allows more light through the lens which defeats the purpose of a sun lens, which I suppose has some merit. I like the enhanced sharpness you get with both sides coated and use polarized lenses to take care of the glare.
Darn typos...should have reviewed it first
Nicko-
Could you explain how an AR coating lessens the natural abberations effect? I don't think that is possible.
You know we wonder how important this feature is. All of my sunwear have backside AR. So last year I got a fancy looking Humphrey pair that I wore over my contact lenses, and does not have backside AR. Horrible to look through, too much reflection.
Yeah, busted by my semantics I guess. I didn't mean that any higher order abberations would be taken away, which if my sentence was taken literally, I suppose you could draw that conclusion. Simply put, when the internal and external reflections are taken away, it makes for less strain on the vision which anti reflection coatings are all about. No more, no less...is that ok with you?
The only sun lenses we will dispense are polarized and they all have a backside AR. Once you have had the opportunity to try it with and without you will immediately become a fan. The patients that previously had polarized without now comment on how their eyes are more relaxed with the backside AR.
Walmart has even figured it out. Their polarized have a backside AR with or without a frontside mirror. Not that we should all copy Walmart but they do have a much higher percentage of clear AR sales than most. I guess when AR is included and not an option you sell more and can charge more for the lenses.
Also, you don't have to get the Essilor sun AR. Any coating lab should be able to do the same coating. Thermal hard coat, backside AR and frontside hydrophobic/oleophobic layer. The Essilor marketing machine strikes again.
My coating lab has been doing this at request for years just like all their AR has been ant-static for years. Lets see, Crizal Alize with Clear Guard was launched not that many months ago as the greatest AR with the new antistatic properties leading people to believe they were the first. I think they were the fourth or fifth and years later. I will end my Essilor rant now.
HUH? If we tried to match the curvature of the cornea we would have some pretty darn steep lenses.
Putting AR on the back side reduces reflections and glare when the sun is behind the patient, which in some circumstances can be quite blinding. Fishermen prefer some sort of side shield to keep out even more glare.
Don't think AR reduces internal reflections on either side of the lens.
AR is delicate and sunglasses are subject to more abrasion from sand, and the like. On the front it would scratch far too easily. Plus as previously stated, who needs something on a sunglass that lets in more light?
Chip
I think ShuString is talking about a proper wrap which reduces unwated backside glare by not allowing light to enter through the backside of the lens.
Exactly Braheem24, although AR can get relections off the inside of the lenses, we can also choose a frame that wraps around keeping the back glare from entering the inner surface. hence my comment:
(A proper fitted frame will solve some of that issue too.)
Chip, I am a little surprised. You keep telling us about the superiority of glass lenses to plastic visual wise. I thought you would be for the improvement of vision on sunglasses.
You would be surprised about the difference still in that situation.
Just curious, do you specify a certain AR coat for the back side? Similar to specifying an AR for a clear pair of glasses (ie Teflon, Zeiss SET, Crizal). My lab says they use the Zeiss SET for the backside.
And what do you guys think of Crizal Sun?
Last edited by DrNeyecare; 07-04-2007 at 06:33 PM.
Not exactly sure. We used the Xelois thing by Essilor in previous years and never had troubles. Now the company is pushing Crizal Sun for more. I have been using the trio sun and I think it will hold out the same.
Not all AR can go on just the backside. That's why they came up with Crizal Sun. We use either Zeiss SET or Crizal Sun. Carat AR and Crizal/Alizé have to be on both sides. If you tint a lens that is already edged you can't put Crizal Sun on it. But polarized lenses with Crizal Sun = the best! Looks much nicer than the SET because of the greenish color and the hydrophobicness (yes, I made that up).
Brown polarized and Zeiss Gold is a very nice looking combo!
Where did you get this info from. I think it more depends on the processing than the coating.
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