I know what size I need-- and I can try these on to see if they work
But I have 100 or so glasses of varying magnifications and I want to
sort and label them.
Is there an easy/cheap method of measuring magnification?
Web searches are just turning up pages telling me how to figure out
what strength I need. I want to know what strength I *have*.
I got some Zenni glasses
which I wasn't sure about the strength. A small town optician did them on
his machine for me, no charge. That was totally nice of him, and I did
thank him for his time.
BTW, the folks on another Usenet list rave about Zennis, and I have bought
from them. I've been very pleased, also.
Christopher A. Young
Learn more about Jesus
Is it do -it-yourself or do you need their trained optician to do it?
On Mon, 18 Mar 2013 10:21:02 -0400, "Stormin Mormon"
I've recently bought a few pair from Zenni (wearing a pair now ;).
Other than the selection of frames isn't great, they're well worth
what I paid. I took one pair to my OD. They were shocked when I told
them that they were from Zenni. The Doc said they'd never seen lenses
done so well, purchased over the Internet.
On Monday, March 18, 2013 10:07:48 AM UTC-4, firstname.lastname@example.org wrote:
The optician does it.
Somehow I doubt that you'd convince one to go through 100 pairs of glasses.
If you've got 100 pairs of glasses hoarded away, you might want to seek help
because that seems pretty OCD to me.
You can find the focal length by focusing the sun (parallel rays) on a
target and measuring the distance from lens to target. (To state the
obvious, the target and lens have to be at right angles to the sun 'rays'.)
"A ... diopter, is a unit of measurement of the optical power of a lens
or curved mirror, which is equal to the reciprocal of the focal length
measured in metres (that is, 1/metres)."
[An ophthalmologist I go to said lenses with the same diopter may not be
the same, which does not make sense to me. He also said he could not
give me a strength for reading glasses from the prescription he wrote,
even though the prescription seems to be in diopters.]
1st of all, he may have been referring to other specs on lenses like
astigmatism, which is the difference between horizontal and vertical
magnification. Plus there are others, which are way beyond my
understanding. But, if he won't give you the information, find a new
eye doctor. BTW, someone once told me to never go to an ophthalmologist
for fitting glasses .... optometrists do a better job because this is
what they do. And, not all optometrists are created equal. As for
'readers' it's not that big a deal, unless you have a more complicated
prescription. Use what works for you for the task you are doing.
Actually, my wife has a very difficult prescription for contacts,
however, any readers work for her ... she uses mine.
Astigmatism is a little more complicated than that. There is an angle
thrown in there, too. Basically it's the difference between a
spherical lens and a cylindrical lens, with "strength" and angle of
Not all ophthalmologists are created equally, either. ;-) However,
if you don't have any abnormalities, going to an MD is a waste of his
time and your money. You're better off with a good OD (how to find
one is another issue). An OD can easily refer you to an
ophthalmologist, if necessary.
Prescription "readers"? I thought the definitions were opposite
(prescription, off-the-shelf). I do have prescription glasses for
reading but I've never heard them referred to as "readers".
Some can't be fitted for contacts at all.
Strange. She must just be near sighted. I wouldn't think that would
be a problem for contacts at all.
Obviously there's some details missing here.
If, as you say, " I can try these on to see if they work for me..."
then aren't those the only ones you need to know the magnification
off? Find all of the ones that work for you, take them to any store
that sells reading glasses and follow the instructions on how to
choose the mag power you need. Once you know that number, it should be
the same as the ones "that work for you".
Now, if you want to label all of them so you can donate them in an
organized manner, then I say "Good for you, that's nice!"
Some lenses are marked, but you can't see them under normal condition.
Take a flashlight and shine it into the edge of the lens. Outside the
field of vision, you may see the markings. I wore glasses for decades
and one day my eye doctor showed me that.
Rather than sort and label them, put the to good use by donating them
to the Lions Club. They will fit them to a happy recipient someplace
in the world.
Look down at some print or other object on magazine, etc. Use ruler or
micrometer to measure height of object. Divide into height of with
magnifier held an inch or two away from object, by height of object. Keep
back a foot or two. Object must be decent size.
What's so hard about magnification.
Use the lens to project a distant scene on a sheet of paper. Then
measure the distance between lens and paper to determine the lens focal
length. The shorter the focal length, the higher the power.
Lens power is often expressed in diopters. A diopter is the reciprocal
of the lens focal length expressed in meters. A +1 lens has a focal
length of one meter.
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