It's been a few weeks but I think you will find this one was well worth the wait...
For the old timers: get set to do some UN-learning!
For the newbies: start thinking about everything optical this way!
Don't believe what you read and hear - believe what you have had actual experience with.
<iframe width="560" height="315" src="https://www.youtube.com/embed/WO-hoibxBOY" frameborder="0" allowfullscreen></iframe>
https://youtu.be/WO-hoibxBOY
Some of this was a surprise, but not that much. Dollar for Dollar, Poly is still a better choice, especially when combined with FF processing. However, for nylor and 3 piece, TVX kicks butt. What really surprised me, though, was the ABBE comparison. I would have thought that TVX would have won hands down, but it only squeezed out the win.
Thanks for posting this. It was enlightening.
You are welcome!
John
I agree, worth watching!Originally Posted by lensmanmd
You know I tried the lensmeter mires hoping to see the difference but really couldn't.
I know you can see it when comparing glass and poly.
I wanted to but it just wasn't there.
Tried the +9.00s and some -2.00s.
If you can think of a great example that would show it, let me know.
You did see it was Part I, right?
John
Hi John;
Your entirely right that it's more noticeable comparing CR/Crown to poly, but you could use Dr's Meslin & Obrecht's work on predicted acuities (Snellen) for LCA's;
Prism/Abbe = LCA's
10D poly vs 10D trivex
10/30 = .33
10/45 = .22
Using Dr's M and O's chart they developed, below...
LCA Visual Acuity
0.05 20/21
0.10 20/22
0.15 20/24
0.20 20/26
0.25 20/28
0.30 20/31
0.40 20/39
We can see acuity through poly with 10D prism yields approx. 20/32 acuity, through trivex, approx. 20/27. Giant difference? Maybe not, unless you're the one looking through them!
I only saw blur from chromatic aberration, not color, when I personally experimented with low Abbe materials (strongest meridian is -5.00 at 180). Seeing color, and blur to a lesser extent, will vary depending on object contrast, lighting conditions, and individual sensitivities.
WRT poly cracking, the lens needs to be under stress before it will crack. The stress can "let go" anywhere from weeks to years, in an everyday environment- no soaking is necessary. Exposure to household cleaners, bug and hair sprays, sun block lotions, etc. can speed up the process.
More HERE.
FWIW, I see a cracked lens about once a month, usually full metal frames, almost always poly, at my low volume, dispensing only, office setting. Some of these failures could be due to low quality frames, and/or lenses traced and mounted with minimal precision, although most of my clients come from boutique type opticals, where at least the frames, on average, seem to be better quality than the corporate and warehouse opticals.
OTOH, I've never seen an anti-reflective coated Trivex lens chip, crack, or break in any type of mounting, from drilled, grooved, or metal inserts since I started using Trivex in the early 2000's. That includes folks who have fallen and face-planted, but not including industrial accidents. Moreover, it's the only material I've worked that has never failed due to chips, flakes, cracks, or breakage.
Were those hammered uncuts finished plano 1mm CT? Another reason to surface everything to 1.5mm and use a higher quality anti-reflection coatings. And if we need to convince our clients why they should spend a little more on their lenses, show them this video.
Best regards,
Robert Martellaro
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
The "hammer" lenses were 1.5 CT.
I'm not sure how to say this exactly but it kind of seems like you missed the message of the video?
1) It was about stock lenses. That was kind of the point. It was about the misconceptions of choosing between stock SV uncut Trivex OR poly lenses. I can't think of any situation where I would choose to surface a lens when I could use a stock one. Cost/profit, time, risk, customer satisfaction... the list goes on.
2) "higher quality anti-reflection coatings." Doesn't mean anything! Just because you spent $$$$ on it or it has a super-buzzword-name does't mean that it will not have significant reduction in impact resistance. Heck you may even have a much higher level in cheap crap! In fact I would bet the better the coating the less impact resistance it would have.
Go back and listen to what the lens companies had to say again.
John
For RXs as you described, I wholeheartedly agree. Based on the video with run of the mill scripts, poly is more cost effective and the general public would be perfectly fine.
John, sometimes I'm just a big dummy!
I have been using free-form generated, position of wear optimized, dip-coated AR lenses for the last 10 years. As noted above, I won't use Poly because it's unreliable. Moreover, finished lenses will be archaic in five years, and ten years after that will probably be 3D-printed.1) It was about stock lenses. That was kind of the point. It was about the misconceptions of choosing between stock SV uncut Trivex OR poly lenses. I can't think of any situation where I would choose to surface a lens when I could use a stock one. Cost/profit, time, risk, customer satisfaction... the list goes on.
It means a higher density oleophobic coating that lasts much longer, and we all know how much that chemical "pill' costs $$$$.2) "higher quality anti-reflection coatings." Doesn't mean anything! Just because you spent $$$$ on it or it has a super-buzzword-name does't mean that it will not have significant reduction in impact resistance. Heck you may even have a much higher level in cheap crap! In fact I would bet the better the coating the less impact resistance it would have.
Go back and listen to what the lens companies had to say again.
John
Although impact resistance is variable (some cushion coats increase the impact resistance), and depends on factors as obscure as the base curve (flatter is less impact resistant), I wouldn't wear or sell that poly lens that you exploded with what looked light only moderate force, although it must be noted that adding an AR stack would probably reduce the impact resistance more on the Trivex than the Poly.
Regardless, if Trivex broke that easily, I'd bump the thickness to 1.8mm, and sleep better at night knowing that mom won't get a cut cornea when a wind gust slams the corner of the car door into her eyeglass lens.
https://www.ncbi.nlm.nih.gov/pubmed/16510343
Not necessarily form broken lenses, but these numbers are shocking. That said, I wouldn't be surprised if eyeglass wearers had fewer eye injuries than folks who didn't wear eyeglasses.
Best regards,
Robert Martellaro
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Robert,
Two things come to mind here.
1) With 100% sincerity I'd love to know your price schedule. From a business standpoint I cannot for the life of me figure out how you can stay in business. I can buy a set of poly, AR coated lenses for $XX.00 and sell them all day long for almost $XXX. Pay my own salary and help my employer keep the lights on, pay the bills, offer perks and ultimately put some money in his/her pocket too. A lab surfaced set of free-form SV lenses with a high-end AR may well be costing you what, $XX, over $XXX? Add in turn-around time and warranty issues and well all I see is a disaster waiting to happen. I'm the opticianry is business guy so (please) help me to understand. I mean both the dollars and sense part and the deeper philosophical part of how you work with your customers to sell a product like that. Looks like you have been doing this a long time so it must work! Tell us more, tell us more!
2) I think you are saying the same thing just in a little different way (maybe)? But, the entire point was without individual testing by a real engineering lab you have no idea how ANY lens will perform. You are tossing around all kinds of words and possible combinations of design and coatings but that only makes things worse not better. I'd push you and ask, "Are you sure that 1.8 with Super Gorbot-7 AR is really going to perform well in impact testing or do you just think it will? Has that combination actually been tested or are you working on assumptions?
(great stuff, Thanks)
John
Last edited by John@OWDC; 11-03-2017 at 08:23 AM. Reason: Its OptiBoard where it is still 1997...
No wholesale costs on this forum please.
I'm Andrew Hamm and I approve this message.
But anyone can take 5 minutes on Google and find the wholesale costs of anything?
Yeah, sure even 5 years ago that made sense but now?
Seriously?
Silly, next time I want to pull a lens apart with a hydraulic jack (it will be my first) I now know what to choose. But if I'd rather not have a lens spider crack, degrade under chemical exposure or be impossible to see out of comfortably (I'm a 8.50 myope) I know what I'm choosing. A 30 minute video does not change what I have learned over 30 years.
Not sure why some of you guys are bagging on this video.....he clearly stated that these weren't super specific scientific tests done in a laboratory. Everything I've always heard has given me the assumption that Trivex is hands down superior in every way compared to Poly yet his video shows it's minimally better, if that. Definitely not worth the cost up charge for me and my patient in return. Great video! I've always wanted to see tests and comparisons like you did. I look forward to part two and other throw-downs----maybe hi index vs. poly, etc.
:D
Jedeye,
So glad you liked the video.
Overall I'd say that comments here were quite positive and some even helpful to me.
Looks like you are pretty new here --- if you thought those comments were bagging on me - whoa - hold on to your hat.
These were all warm and fuzzy to what you may read.
Just part of the social media of optical I'm afraid.
Still some great minds here on OptiBoard.
John
Our industry is rife with opinions. Fortunately, most OBr’s are well versed, allowing for vigorous conversations with minimal “hurt” feelings.
The manufacturing side tends to weigh the cost/benefit ratio. Those on the other side of the glass weighs benefit/clarity ratio. Both are correct and both have their challenges. This is what makes this forum great.
All I'm going to say is that for very many years I've used polycarbonate almost exclusively.
For dollars to donuts, polycarb is the best material.
If rimless, you should do trivex when possible, however.
If you need edge thickness reduction, you should do 1.67 because it's available in everything and it's only super-expensive, not mega-expensive.
I was late to the "trivex party" because of some of the places I've worked. These days I heavily push for it in certain frames (the kinds most others here describe) and I always offer it or Cr39 or 1.60 as superior optically, but I don't push hard on it because for the money Polycarb is a wonder material for most people.
Diminishing returns on investment, but many people still want the best no matter what. Also on plus lenses I think it's optics really shine compared to polycarbonate.
I found it to be a very interesting video! Thanks for the post!
Can we talk?
I really don't know the answer to this.
As a myope, the prism is at the bottom of the lens, so the chromatic aberration is at the bottom of the lens.
For a higher hyperope, despite the thicker center, the prism is still just as far away from the optical center as with a myope. So it's a wash, there.
However, as a myope I'm looking mostly through a thin lens...maybe 2-4 mm in straight-ahead gaze. What about a higher hyperope looking through 8mm plastic? Seems like it would be worse.
+1
This is a great group to put you in your place when you have no clue about your wrongness. And I love it.
Have I told you today how much I hate poly?
I was shocked how easily the poly lens broke when hit with a hammer! Otherwise, no surprises. I used to think trivex was as impact resistant as poly but I learned awhile ago(maybe on optiboard) that it's not when coated.
But again- that poly and the hammer! ��
I'd suggest tossing this up on Ask The Lab Guy or maybe even The Optical Society (both on Facebook)?
Outside my pay grade!
Well, outside my brain capacity to be honest.
Does light scatter more in a thicker medium? Of course it would.
Is it "significant", i.e., can humans tell? I don't know.
Is it material dependent, or "purity" dependent? I don't know.
There are currently 1 users browsing this thread. (0 members and 1 guests)
Posting Permissions
Reply With Quote
Bookmarks