In the term "20/20 vision" the numerator refers to the distance in feet from which a perso
n can reliably distinguish a pair of objects.
Twenty feet is essentially infinity from an optical perspective (the difference in optical power required to focus at 20 feet versus infinity is only 0.164 diopters). For that reason, 20/20 vision can be considered nominal performance for human distance vision.
Posted By: Arizona Bay on July 18th 2008 at 11:59:48
Message Thread
- 20/20 vision. What is that? I've never really known. (n/m) (General Chat) - CB41, Jul 18, 11:56:30
- In the term "20/20 vision" the numerator refers to the distance in feet from which a perso (General Chat) - Arizona Bay, Jul 18, 11:59:48
- But why 2 "20's"? Is it one for each eye? If so, (General Chat) - CB41, Jul 18, 12:09:02
- No, it's not one for each eye. (General Chat) - Arizona Bay, Jul 18, 12:16:10
- Blimey, not sure I'm glad I asked now:-( (n/m) (General Chat) - CB41, Jul 18, 12:17:46
- No, it's not one for each eye. (General Chat) - Arizona Bay, Jul 18, 12:16:10
- 6/6 is the closeup version (General Chat) - camcan, Jul 18, 12:01:02
- I always thought[*] that 6/6 was the metric equivalent of 20/20. (General Chat) - Arizona Bay, Jul 18, 12:02:25
- Happy to be proved wrong (General Chat) - camcan, Jul 18, 12:04:10
- I'm seriously considering laser eye surgery, but don't mind admitting to being a little sc (General Chat) - Arizona Bay, Jul 18, 12:08:22
- It's a tough call (General Chat) - camcan, Jul 18, 12:11:34
- Don't think I'd get on with contacts. I am very squemish about putting thing in my eyes. (General Chat) - Arizona Bay, Jul 18, 12:23:19
- have you tried specatacles? (n/m) (General Chat) - Tomblander, Jul 18, 12:25:54
- Yes, I like my specs. (n/m) (General Chat) - Arizona Bay, Jul 18, 12:27:05
- have you tried specatacles? (n/m) (General Chat) - Tomblander, Jul 18, 12:25:54
- Don't think I'd get on with contacts. I am very squemish about putting thing in my eyes. (General Chat) - Arizona Bay, Jul 18, 12:23:19
- Don't put them up your arse then. This will help in two ways: (General Chat) - CB41, Jul 18, 12:10:52
- It's a tough call (General Chat) - camcan, Jul 18, 12:11:34
- I'm seriously considering laser eye surgery, but don't mind admitting to being a little sc (General Chat) - Arizona Bay, Jul 18, 12:08:22
- Happy to be proved wrong (General Chat) - camcan, Jul 18, 12:04:10
- I always thought[*] that 6/6 was the metric equivalent of 20/20. (General Chat) - Arizona Bay, Jul 18, 12:02:25
- But why 2 "20's"? Is it one for each eye? If so, (General Chat) - CB41, Jul 18, 12:09:02
- when you can watch cricket without going mad from boredom (n/m) (General Chat) - Dave in France, Jul 18, 11:58:02
- In the term "20/20 vision" the numerator refers to the distance in feet from which a perso (General Chat) - Arizona Bay, Jul 18, 11:59:48
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