Archived posting to the Leica Users Group, 2001/08/13

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Subject: Re: [Leica] M6 correction lenses--Win<>Win
From: Dennis Painter <dennis@hale-pohaku.com>
Date: Mon, 13 Aug 2001 07:07:47 -0700
References: <006901c124a3$2f405920$0201a8c0@Workgroup>

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

In reply to: Message from "Frank Filippone" <red735i@earthlink.net> ([Leica] M6 correction lenses--Win<>Win)