Difference between revisions of Diopters
Jump to navigation
Jump to search
No edit summary |
No edit summary |
||
| Line 7: | Line 7: | ||
* Lenses in series add their powers: if you're wearing -2 diopter contacts ([[vertex distance|adjusted for glasses strength]]) and put +1 diopter reading glasses over the contacts you're in effect wearing -1 diopters. | * Lenses in series add their powers: if you're wearing -2 diopter contacts ([[vertex distance|adjusted for glasses strength]]) and put +1 diopter reading glasses over the contacts you're in effect wearing -1 diopters. | ||
** There are some caveats such as vertex distance, since moving the lens away effectively gives you a weaker negative lens or stronger positive lens. | ** There are some caveats such as vertex distance, since moving the lens away effectively gives you a weaker negative lens or stronger positive lens. There is also decentration, which induces prism when the lens is moved to the side. These effects become negligible for weaker lenses. | ||
* According to the thin lens sign convention, negative focal power is diverging, and positive focal power is converging. | * According to the thin lens sign convention, negative focal power is diverging, and positive focal power is converging. | ||
** A lens with a negative diopter sign compensates for [[nearsightedness]] while a lens with a positive diopter sign compensates for [[farsightedness]]. | ** A lens with a negative diopter sign compensates for [[nearsightedness]] while a lens with a positive diopter sign compensates for [[farsightedness]]. | ||