From: Optical@Guy.com   
      
   Salmon Egg wrote:   
      
   > > Some claim that reading glasses work because they magnify small   
   > > print. They claim that reading glasses sold at drug stores are   
   > > labelled in terms of their "magnification power" or strength.   
   > >   
   > > I was arguing that the goal of reading glasses is not to magnify,   
   > > but to move the focal point, and that they don't really perform   
   > > any magnification.   
   > >   
   > > Who's right?   
   >   
   > BOTH!   
   >   
   > The lenses for reading glasses are converging or positive lenses.   
   > They have many applications. They can be used as magnifying lenses   
   > of the kind pictured being held by Sherlock Holmes.   
      
   I was not talking about using the lenses for anything other than being   
   worn on your nose.   
      
   I was trying to make the point that when you quickly move a pair of   
   reading glasses quickly on and off your nose, that they don't seem to   
   make any apparent change to the size of text that's held close to your   
   face, but they do change the focus of the text so that it's easier to   
   read.   
      
   Hence my argument that even though they're commonly referred to as   
   magnifiers or performing some sort of magnification or even labelled in   
   terms of magnifying power, they really don't seem to magnify as part of   
   their design specification (when used as reading glasses, as worn on   
   your nose with the lenses just a fraction of an inch in front of your   
   eyes).   
      
      
      
      
      
      
   Weaker versions have been   
   > used as reading glasses, and they move the image of what you are looking   
   > at to focus on your retina. Stronger versions can be put close yo the as   
   > with jeweler's loupes. These really are like reading glasses but you   
   > bring what you are looking close to the eye.   
   >   
   > Bill   
   >   
   > --   
   > An old man would be better off never having been born.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)