Archived posting to the Leica Users Group, 2001/08/13
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Frank Filippone wrote: > OK..... Here goes my ignorance of eyeball optics...... > > My normal right eye long distance prescription is 1 diopters. Is that MINUS > or PLUS ? > Do you add or subtract -0.5 to that number to get the correct lens for the > camera to come out right? <snip> Always add. But remember when you add a negative number it subtracts from the sum. And two negatives are summed to a negative result. - -0.5 added to +1.0 = +0.5 - -0.5 added to -0.5 = -1.0 If your prescription has a - in front ot the numbers it's minus, otherwise plus