General Question

keobooks's avatar

How do I determine the magnification of a magnifying glass?

Asked by keobooks (14322points) April 26th, 2013
8 responses
“Great Question” (3points)

Someone gave me this cool magnifier. It’s been neat to look at things, but I’d like to know the magnification. The product’s identifying code written on the side were “Radio Shack 63–1302” which is now the code for a thermometer they sell. So I am guessing the product is older.

I looked online for similar looking magnifiers and couldn’t find anything that looked like it. I was assuming I’d find a look-alike like all 10x loupes are about the same size, so I’d find a loupe that looked like this one—but I couldn’t find one that matched.

My last resort is to find a really friendly jeweler and ask them what they think it is. But that’s relying heavily on their kindness.
So I wondered if anyone here had an idea of how to find out the magnification.

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Answers

keobooks's avatar

Oh man—I should have posted that I already looked up this stuff and it was WAY over my head. I don’t want to do math. I just want to know what I am playing with.

RocketGuy's avatar

Get the lens to focus an image of an object (e.g. light bulb) on a piece of paper. The ratio of the distance of object to lens vs distance of paper to lens is the mag:
https://en.wikipedia.org/wiki/Magnification

keobooks's avatar

Don’t hate me for this. I kept searching for different types of magnifying products and FINALLY found several look-alikes that matched the dimensions perfectly. It turns out to be a 5x magnifier meant to look at old photographs, slides, or crime scene pictures.

Forgive me, I just suck at math and am fairly good at researching stuff.

LuckyGuy's avatar

Does it look like this one ? They call it a 30X but it is really the square root of 30 or 5.5x.
I have one of them – and mine is in much better shape than the one on ebay.

keobooks's avatar

No. It looked more like this. I found a Bauch and Lomb one very similar that also gave the specs (2 inch lenses, 2 inch focal point) and I measured the one I had to make sure it was the same.

I’m in the middle of stuff so I can’t find the page and it was hard to recreate the search I did. So I just looked up a similar one without the specs that the Bausch and Lomb one had.

LostInParadise's avatar

I see that you found the magnification. I was going to suggest a very easy way of estimating the magnification. Just put two rulers near each other so their scales are parallel. Place one of them under the magnifier and see where the image of the one inch mark comes up on the unmagnified one.

keobooks's avatar

I will remember that next time, @LostInParadise That’s more my style of doing it.

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