Light streaking through new spectacles. Even company can't solve. Please help.

[PartTimer]

HEY, ME TOO!!!

Seriously, though. Never heard of altitude as a risk for crazing.

[lensmanmd]

Put me on this list, too.

This altitude thing is a bit disconcerting. Thin films are applied in vacuum, then brought back to atmosphere to unload, so altitude should have nothing to do with this. However, the constant change in cabin pressure during takeoff and landing, as well as subtle changes in flight does make one curious. Also makes me wonder what kind of chemicals are used in the air scrubbers in-flight?

[drk]

Not to derail, but I know nothing about the AR process.

You essentially spray molecules/ions/atoms on to a lens? Why the vacuum? So there's no interference from air molecules?

[Robert_S]

So there can be no dust particles is the main reason for the vacuum

[drk]

Thank you.

So the atmospheric pressure on a lens coating is initially zero, but then it gradually gets a very teeny-weenie atmospheric pressure applied once it comes out of its incubator. Virtually nothing at all on Earth.

Now if we put this teenie pressure on the stack, and then reduce it, then put it on, then reduce it, such as would be the worst-case scenario in an airplane...

...it wouldn't amount to a hill of beans.

We'd be better off postulating on greater exposure to gamma rays in high altitudes, right?

[Chris Ryser]

Looks like a simply scratched coating.

[rbaker]

Y'all might want to Google "vacuum deposition." Wikipedia is a good place to start.

[debayandas]

Or maybe is it possible that the pilot has say 20℃ cabin temp, and when he opens the door in Greenland or Alaska or Siberia, bam! It's -30℃. Same might happen when he lands in desert countries when the outside temps can be as high as 45℃. The rapid contraction and expansion adds up daily over 6 months. Just my two cents.

[rbaker]

How come the coatings on my camera lenses have not had any degradation in the 56 years that they have been exposed to extremes of temperature and altitude. The coatings are as pristine as the day I purchased them. Could it be that they were never cleaned with solvents and paper towels.

[lensmanmd]

How come the coatings on my camera lenses have not had any degradation in the 56 years that they have been exposed to extremes of temperature and altitude. The coatings are as pristine as the day I purchased them. Could it be that they were never cleaned with solvents and paper towels.

That, and glass does not expand and contract like today's lens materials. The SI layer is basically a thin layer of glass. My L series, as well as my Tamrons are just as good as the day I put them on my camera, too. Heck, I have a set of Pentax lenses form the early 50s that I still use on my film body.

[Tallboy]

My next suggestion for him is glass unless I find a solution. Trying trivex this time just because wanted to, but not expecting it to help.

[Quince]

Wow, I missed a lot on my day off! This thread makes for a good read though. Lots of gears turning and minds coming together through experience. I smell Hall o' Fame potential...

[lensmanmd]

Hey Doc, this does not cover the particulars of lenses, but does cover the deposition principles. http://www.pfonline.com/articles/vac...oating-options For lens info, check out https://qtmi.net/ This is the process that we employ. You will find a great deal of info here. Outside of Zeiss, Essilor and Hoya, many labs incorporate Quantum's processes.

[drk]

Thanks! I'm going to nerd out and read it.

[MIOPE]

Look like is a case of cracked coating. BPI sell a product that remove AR and if the lens is left more time it will remove coating too.
This could solve the mystery.

[debayandas]

Amazing forum! Thank you so much for the awesome brainstorming.

I was thinking, will Polycarbonate be a better option for the customer? Does poly resist more stress fractures, heat expansion and AR cracking due to expansion, than CR-39 that he is using?

[Chris Ryser]

That, and glass does not expand and contract like today's lens materials. The SI layer is basically a thin layer of glass. My L series, as well as my Tamrons are just as good as the day I put them on my camera, too. Heck, I have a set of Pentax lenses form the early 50s that I still use on my film body.

The layer of AR coatings is made with SIO2 which is glass very thin and hard, that adheres to the hard coat on plastic lenses of whatever the plastic material is.

You are bound to get contraction and expansion of the lens material with extreme changes in temperature and therefore also cracking and delamination.

I came up with the first AR Stripper in 1983 when the problem was a lot worse than it is today, due to better adherence to the lens by technical improvements.

Removing the AR coating today is easy and fast, however these products are made with one of the most dangerous acids on the globe.

See the information to all of it at:
http://optochemicals.com/arstripper_info.htm

[debayandas]

Will stripping off the AR coating strip off the UV and transitions too?

[lensmanmd]

Will stripping off the AR coating strip off the UV and transitions too?

It will not, but it may affect he hardcoat if left too long, rendering the lens unusable. Wear gloves and goggles, AR stripper is basically a glass etching acid, very caustic.

[drk]

And turns polycarbonate into milkycarbonate.

[Uilleann]

That is crazing - almost certainly from either high heat, or temp change. Or I'm a monkey's uncle. Or at least your father's brother's nephew's cousin's former roommate.

Chemicals or altitude are extremely unlikely culprits. In fact, I've never seen a lens craze due to altitude in particular, and that's with years of flying under my own belt, as well as making glasses for pilots from numerous major airlines, small regional carriers, cargo outfits, charters, and of course the AF base and ANG base here as well for more than 30 years. Literally never happens.

It can happen when a pt flexes their lenses the wrong way (they'll never admit this of course) - particularly in a grooved rimless. And of course, it could come down to just sloppy finish work at the lab level. It may show up immediately, or weeks or even months later. It isn't brand specific. Crizal, Zeiss, Hoya, et al will ALL do the same thing under the right circumstances. Can you just have a new set remade under their lens warranty? Try 1.60 instead of poly perhaps...and maybe suggest a full frame design to minimize the chance of that occurring again.

[drk]

It's 1.5.

So you're suggesting it is heat expansion on the substrate lens.

Do we have a metric for "expansion"? Which lens type is most likely to expand/contract?

Urethane lenses (I think that's what high index lenses are...?)
Polycarbonate
Trivex
Resin lenses (what are those, again?)
Glass

[drk]

I did an internet search. All I could come up with is some crackpot site. Probably fake news: http://www.optiboard.com/forums/show...Weather-and-AR

[Uilleann]

It's 1.5. So you're suggesting it is heat expansion on the substrate lens.

With that pattern, I'd say it's the culprit 99.999% of the time.

[drk]

debayandas: Is it possible your patient has very nice air-conditioning and goes out into the Indian heat?