determine magnification of reading glasses

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I know what size I need-- and I can try these on to see if they work for me--
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*.
Thanks Jim
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I assumed you've checked this already, but I'll toss it out there anyway...
Some brands put the magnification strength on the arm, either engraved in or printed on the rubber ear cushion.
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On 3/18/2013 6:59 AM, DerbyDad03 wrote:

Go to Target or Walmart. Their eye glass place has a machine that can tell what the strength of the eye wear is. Probably do it for nothing but a tip might help.
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y...

in

Is it do -it-yourself or do you need their trained optician to do it?
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I got some Zenni glasses http://www.zennioptical.com/ 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 www.lds.org .

Is it do -it-yourself or do you need their trained optician to do it?
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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.
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On Monday, March 18, 2013 10:07:48 AM UTC-4, snipped-for-privacy@sbcglobal.net 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.
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On 3/18/2013 10:07 AM, snipped-for-privacy@sbcglobal.net wrote:

The lady that helps you find frames, etc. offered to help me with a few of my glasses. I didn't have 100. Just a few. Chuck B
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On 3/18/2013 4:35 AM, Jim Elbrecht wrote:

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'.)
According to http://en.wikipedia.org/wiki/Diopter "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.]
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On 3/18/2013 11:13 AM, bud-- wrote:

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.
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wrote:

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 the cylinder.

+1

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.
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Thank you. This was very helpful
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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!"
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Donate to the Lions club used eyeglass drive.
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wrote:

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.
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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.
Greg
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Interesting that with all the replys to this thread, only one, Bud, actually answered the question.
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Did you ever find a 'do it yourself gadget to measure power of reading glasses?
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On 8/11/2016 10:35 PM, snipped-for-privacy@gmail.com wrote:

1/u + 1/v = 1/f
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snipped-for-privacy@gmail.com wrote:

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.
Fred
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