Thanks for the information. These magnifiers do say 8X and 10X they don't give
the diopter. They are round and they are clear image just not as large as they
should be.
----- Original Message -----
From: "Kathy Seven Williams" <kseven@...>
To: <magnifiers@yahoogroups.com>
Sent: Saturday, October 25, 2008 8:33 PM
Subject: RE: [magnifiers] Magnifier standards


Magnifiers vary extremely in quality. If you have ever been fitted with
glasses you'll remember the better worse game which those of us with low
vision usually only can play in full diopter increments, but which others
play in quarter diopter jumps. Better worse adn be at the same magnification
with other perameters changed in the lense. Also a well cut, finely made
lens is going to give clearer magnification than the plastic one from the
crack-n-the-Jack box (look ma! no copyright infringement)... If you can see
the difference, good magnifying glasses are a better buy. If you can't see
it, don't bother.

There are all sorts of formulas I no longer remember about magnification
because I haven't worked inthe field for decades now. But magnification on
your CCTV is different from that with your hand held lens. 16 diopter
handheld lens will give you 4 X magnification I believe in other words it
takes 4 diopters to increase the image one time height and width. Some
devices such as bar magnifiers only magnify in one direction so you get tall
skinny characters when looking at print with the height magnified and the
width left alone.
So my expensive specticle mounted 65 diopter magnifier is giving me just a
tad over 15X magnification. Do the math as I"m too old for it, but this
means that the 5 X magnifier is 20 diopters and the 8 X is 32 diopters.
Differences can certainly be accounted for by quality of lens and
manufacturing standards. That much of a difference so you'd read better with
the 5X than the 8X...possibly. But be sure you're comparing apples to
apples. Is the 8X really 8X or is it 8 diopters which would only give you
2X? That would make a huge difference.

If you wish to prolong this headache go read
http://www.bertech.com/product8/magnifi_notes.htm
for the details in other words probably more accurate than mine.

A lesson here is if you ccan't afford the expensive, good quality lenses,
get a stronger lens in the lower priced version than you think you need and
give it a go.

While they were saying among themselves it cannot be done, it was done.
Helen Keller

Kathy Seven Williams






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