4 ms·
Hear, hear! Here's a good way to test your glass's refraction index. On your desktop find a small red icon with something white in the center. Stare directly a
by globnomulous 2y ago
Hear, hear!
Here's a good way to test your glass's refraction index. On your desktop find a small red icon with something white in the center. Stare directly at it. Now turn your head until the icon is at the edge of your vision. If your lenses are cheap polycarbonate, the white part of the icon will appear to move towards the edge of the icon or even out of it.
Most non-cheapo glasses today in the US use Trivex. It's a polymer, not glass, but its Abbe number is 43, which is perfectly adequate.
Crown glass, with its Abbe number of 59, is superior, but the eyeball can discern differences only up to 45-50, so most of Crown glass's improvement over Trivex is imperceptible.
This is partly why it's not offered in glasses (again, in the US, at least according to my optometrist). It is also twice as heavy, shatters (polymers like Trivex don't), and scratches more easily.
- walterbell 2y agoAmong non-glass options, CR-39 is a good choice for computer glasses with prescriptions weaker than -5: - high (58) Abbe number - thick (1.5 index) - cheapest Thickness and weight can be mitigated with a smaller frame, e.g. vintage options. Actually buying CR-39 lens might require solving a dark pattern maze of online or offline options, since the cost is so low.
- fy20 2y agohttps://www.selectspecs.com/ https://www.selectspecs.com/ if you are in Europe. I've been using them for years.
- AceyMan 2y agoMy indoor (non Transitions™) multifocus² glasses are CR-39¹. I'd used the same material for my outdoor/sports/driving frames but it's higher density caused them to slide down my nose during activity so the next pair I opted for Trivex. -- ¹–CR-39 requires full frame spectacles, as drilling holes is verboten. ²–Shamir Autograph III, awesome & highly recommended.
- Suppafly 2y agoI don't know which type of glass my glasses have, but I know I had to pay a ton for it, because the cheaper sort can't handle my prescription without being really thick and/or heavy. But as someone that actually wears my glasses all the time and not just randomly, it's worth the extra expense.
- globnomulous 2y agoInteresting, is the lens ultra high-index? How's refraction? As far as I'm aware, high-index, as the index becomes higher, generally will have a progressively worse Abbe number.