Don't hold me to this, but judging from your computer and reading numbers (-4.50 and -4.00), I'd come to the conclusion that for each +0.50 of ADD power, it's going to shorten your focal length by 4 to 5 inches. But, I'd try Paul's experiment, as it will be more accurate and won't cost you a penny to try.
-=# Firewalker #=- On Jun 21, 4:41 pm, sj <[email protected]> wrote: > I have a similar question. My official prescription has an ADD of > 1.75, and while that may be OK for casual reading, it puts the in- > focus zone too far out for some things I want to do (Crafts and small > electronics assembly). I have some single vision close-up glasses > right now. Rough estimate of my usful focus distance with these > glasses is - > -4.00 (reading) 16 to 20 inches (this is +1.75 from my distance > prescription) > -4.50 (computer) 20 to 25 inches > > I'm going to get a couple more pairs of $8 Zenni's, but I'm undecided > on how large of a step down to try. Any comments or ideas welcome. > > On Jun 15, 7:11 pm, GrantC <[email protected]> wrote: > > > > > My prescription has an ADD number of +1.75 for each eye, which is > > perfect correction for a 12" distance. Suppose I want to change that - > > let's say I want an 8" distance, or a 16" distance. > > > Now, my logical mind says a correction for 8" would be +2.50 (or > > perhaps +2.75), while a 16" would be +1.25 to +1.50 > > > How far off base am I? > > > -=[ Grant ]=-- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
