Hi,
I saw someone advertising 1.9 index lens from Zeiss....but in glass! First of all I thought we can't get index higher than 1.74 in the US. Secondly is is impact resistant glass? Can we get higher index than 1.74 in plastic in the US?
1.9 index lens?
Hi,
I saw someone advertising 1.9 index lens from Zeiss....but in glass! First of all I thought we can't get index higher than 1.74 in the US. Secondly is is impact resistant glass? Can we get higher index than 1.74 in plastic in the US?
1.9 index glass has been around for over 10 years here. It is only available in single vision, is very expensive and just as brittle if not more so than any other glass lens. It is also very heavy about 4.54g/cm3 if I remember correctly. Avoid like the plague. Choose your frame wisely and stick with 1.74. Your px will thank you for is.
It also cannot be hardened
Avoid 1.9 glass like the plague!! I'm waiting for the 1.80 plastic to be released, supposedly at VEW this year. Also, 1.70 is a better material than 1.74.
Yeah I agree that i.7 plastic is better, but only Hoya do it in the UK, everyone else is 1.67 then 1.74. As I am not a fan of hoya pregressives, it kind of leaves me with no choice.
1.70, 1.80, and 1.90 glass are all available in the US, and in fact we offer all three to our wholesale accounts. Don't sell but maybe 1 every 2~3 months, but it's there if anyone wants it.
I used to have the most beautiful pair of Zeiss 1.90 glass. Then it fell off the counter in the bathroom and broke...... :hammer:
The Zeiss Lantal is no longer directly available in the US, but other vendors still make it.
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
No choice but to give them inferior materials. I wore both the ECP and Summit CD in 1.70 and loved them, when I was a -15.00.Originally Posted by Aberdeen Angus
DragonlensmanWV N.A.O.L.
"There is nothing patriotic about hating your government or pretending you can hate your government but love your country."
I wouldn't say that the 1.67 and 1.74 lenses were so much poorer that I have a problem supplying them. I suppose that it's all relative. Over here polycarbonate is very poorly rated as a lens material and most opticians are loathe to use it for anything apart from safety specs. Some opticians will use it for rimless, but most would prefer to use trivex or 1.6 material. from what I can gather from posts from your side of the pond polycarb is one of the most commonly used lens materials?
That would depend on the optician. Some love it, some hate it. When I was working in a retail enviornment, I avoided it as much as possible. There isn't anything that it does that another lenses doesn't do better. The optics are horrible in it and the manufacturing process by which polycarbonate material is made is horrible for the enviornment.
Poly over here has really benefitted from agressive marketing, both to OD's and Opticians, as well as by larger chain retail stores.
http://en.wikipedia.org/wiki/Polycarbonate
The Wikipedia article is interesting, especially the parts of it that are wrong. I didn't know that CR-39 was really a type of Polycarbonate.....(yes, that's what it says in the article).
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
I prefer trivex over poly too but was unaware of the enviornmental aspext of it. Could you give me more info on that? TY
goodsearch.com vosh
I also am loathe to use poly, but I have to in some cases (Medicaid). Since we changed to require Trivex in all our drill mounts, we have had zero breakages. My biggest problem with 1.67 and 1.74 is that their ABBE value is so low, that when you have a lens that is thick enough to benefit from it's thinness, the customer has problems seeing through it at the periphery. It's fine for less than say, 6.0 Diopters, but when you get up higher, it becomes unwearable, at least for me. For years I wore lenses thicker than I could get because I placed a higher importance on clarity of vision rather than mere thickness. Then Hoya came up with the 1.70 and finally I could get relatively thin lenses with far superior clarity. Trust me, the worse thing you could do for your over 10.D customer would be to put them in 1.67 or 1.74. The voice of experience speaks!
DragonlensmanWV N.A.O.L.
"There is nothing patriotic about hating your government or pretending you can hate your government but love your country."
Dragon, I'd be curious to see how you liked a 1.67 or 1.74 in a Free Form SV. I'm wondering if the accuracy and improved optics that Free From gives would overcome the shortcomings of the optics of the materials.
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
I don't think it would make much difference. AR does nothing to negate a bad ABBE. Now if the FFs were thinner, that would help. But the main problem begins when you have a certain thickness of material to gaze through, and even if it were FFed, once you reach that amount of material to look through, you still have the problem. Now if they can fine tune Freeform to only affect the spectrum (both ends) of light that is misfocused, then you could make any material perform as well as glass.
That makes one of the claims of the Izon lenses a moo point (doesn't matter to a cow.... it's moo) about their magic goo layer. They claim it reduces the aberrations caused by the low ABBE materials. Now think that through..the light enters the front of the lens and gets all aberrated, then passes through the magic goo and gets all unaberrated....then of course, it has to pass through the rear wafer (often thicker than the front) and somehow it stays corrected??
DragonlensmanWV N.A.O.L.
"There is nothing patriotic about hating your government or pretending you can hate your government but love your country."
Might be better, but think how much better it would be if made from 1.70 from Vision-ease, Tokai or Hoya.
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