I don't believe that Zenni uses a true polycarbonate resin, but possibly uses a material call HIRI resin.
Here's a clip from PPG describing HIRI resin: Lenses made from HIRI casting resin are both thinner and lighter than those made of conventional plastic or glass because of the resins higher refractive index (1.56) and lighter weight. Properly fabricated lenses made from HIRI resin are optically uniform, with no waves or inclusions, and they give less chromatic aberration than polycarbonate lenses. Although designed primarily as a lighter and easier-to-cast and high-refractive index alternative to CR-39 monomer, HIRI resin may be used in any application that requires a versatile, easily processed thermosetting resin. At the prices that Zenni charges, it only stands to reason that they are producing/molding their lenses "in-house", and with the volume they output on a daily basis, HIRI would make a reasonable choice due to it's ease of processing and relatively short curing times. -=# Firewalker #=- On Apr 9, 1:32 am, Paul <[email protected]> wrote: > I had largish polycarbonate rimless glasses many years ago that had > serious chromatic aberration. I had to return them. (Prescription was > over -6.00, and I never had a problem with CR-39.) I heard that newer > polycarbonate lenses had improved a lot. > > Last summer I got a pair of rimlesss from Zenni, with a similar > prescription, using their standard lenses. Supposedly they use > polycarbonate, and the lenses were somewhat thick. Very little > chromatic problem, though, and I think I'm somewhat sensitive to it. > Same good results with their 41 mm round metal frames, which had > pretty thin lenses, still using their standard lens material. > > I didn't get antireflective coating in either case, but I don't think > that's what made the difference. --~--~---------~--~----~------------~-------~--~----~ Check us out at the oft-updated http://www.glassyeyes.com! You received this message because you are subscribed to the Google Groups "GlassyEyes" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/glassyeyes?hl=en -~----------~----~----~----~------~----~------~--~---
