It's wrong to consider +3.00 & -3.00 the same. Plus corrections are almost doubly inverse of minus corrections - 1.5x at a very minimum. A +3.00 is at least a -5.00 when comparing severity. Just ask any lab as to which stock lenses they carry, +4.00/-7.00 to -8.00 is probably most common.
Minus corrections are more concerned with edge thickness. Plus lenses can get very heavy. I've seen virtually no one happy with a +3.00 or above in cr-39, or +3.50 in polycarbonate or above. I've dealt with almost 10 optical professionals in 3 states & 2 countries in the past ten years. This is the most common mistake i've seen made by inexperienced personnel. J.evan iPhone On Jun 1, 2009, at 6:45 AM, clarity <[email protected]> wrote: > > I would NEVER use cr39 on a RX over +3.00 or -3.00 unless i HAD TO. > It looks like crap, sorry but like pure crap.It will stick out up to. > 6.7mm i would consider this to be heavy and ugly.Sorry but just > because you want to save money doesnt mean you should buy the cheapest > product available. > Sorry all lenses have abberations, cr39 in one of the most stable > materials in this regard.However, unless you have low vision, or are > unable to be corrected to 6/6 with spectacles you are very unlikley to > notice the difference in abberations if you go for a high index. > > On May 30, 8:52 am, Paul <[email protected]> wrote: >> -4.00 is not that bad. Personally, except for rimless, I would stick >> with CR39 because of low price, reasonably good thickness, and >> excellent optical quality. >> >> If you're getting plastic frames, CR39 is a complete no-brainer. The >> frame will hide any lens thickness, and there's no chance of >> chromatic >> aberration. CR39 is probably not suitable for rimless for other >> reasons than thickness. I would think that it's fine also for metal >> frames unless you're getting really large ones (50+ mm). >> >> Zenni's standard 1.57 "Thin and Light" plastic" (probably the same >> stuff that other places call by that name) should also work fine with >> any frame. > > > --~--~---------~--~----~------------~-------~--~----~ Check us out at the oft-updated http://glassyeyes.blogspot.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 -~----------~----~----~----~------~----~------~--~---
