Difference between revisions of Optics related math
Add placeholders for calculating correction, so I can flesh them out using the section edit |
→From 20/20 prescription: simple geometric argument |
||
| Line 45: | Line 45: | ||
===From 20/20 prescription=== | ===From 20/20 prescription=== | ||
The advantage of calculating the strength of [[differentials]] | |||
as a reduction from full prescription is that you don't have to worry about | |||
the [[cylinder]] element - just preserve that part. | |||
Assuming you are wearing your full 20/20 correction (or even if you are fortunate | |||
to be [[emmetropic]]), the eye wants to receive parallel incident light to be relaxed. | |||
So we can use a simple geometric argument to calculate the strength of the (converging) | |||
lens which should be interposed : an object placed at the focus of a converging | |||
lens will result in parallel outgoing light ("focus at infinity"). This parallel light | |||
is exactly what the (fully corrected) eye wants to receive. | |||
But rather than actually placing such a lens in front of your full prescription, | |||
simply subtract that value. | |||
ie if your screen is 50cm away, that corresponds to a power of <math>\frac{1}{0.5} = 2D</math>. | |||
So that's the value you'd subtract from your full prescription. | |||
===From blur horizon of naked eye=== | ===From blur horizon of naked eye=== | ||