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Thread: Measuring magnification

  1. #1 Measuring magnification 
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    How to Measure magnification
    How can I see how strong a magnifying glass is?


    I bought this magnifying glass http://www.liangdianup.com/inventory/189901.htm and I want

    to know how to test it to see how strong it is. I hear a lot of people talk about

    magnifying and how strong the magnification is, but I would like to know the true

    magnification of my magnifying glass. I have a few of them and some seem stronger then

    others. How can I rate these? How can I pin a correct number on mine? How do the companies

    that make these come up with these numbers.


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  3. #2  
    Forum Masters Degree organic god's Avatar
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    i'm no expert on this but i could hazard a few guesses.

    The company would set an arbritary magnification to be 0, or 1* magnification whatever they call it, and this is how the image appears to the naked eye.

    then they maybe draw a 1mm*1mm square at the zero they set. the square is then magnified and the magnified object area is measured. the new size of the square is somehow proportional to a magnification. (magnification constant?)

    the distance between eye,magnifying glass, and object would need to be kept constant in each case


    everything is mathematical.
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  4. #3 Re: Measuring magnification 
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    Quote Originally Posted by hellogreen
    How to Measure magnification
    How can I see how strong a magnifying glass is?


    I bought this magnifying glass http://www.liangdianup.com/inventory/189901.htm and I want

    to know how to test it to see how strong it is. I hear a lot of people talk about

    magnifying and how strong the magnification is, but I would like to know the true

    magnification of my magnifying glass. I have a few of them and some seem stronger then

    others. How can I rate these? How can I pin a correct number on mine? How do the companies

    that make these come up with these numbers.
    For a single lens the quantity that you are really interested in is focal length rather than magnification per se. You can change the magnification by changing the distance from the lens to the object and then moving your eye to put the image in focus. This Wiki article will explain the mathematical relationship between focal length and magnification . http://en.wikipedia.org/wiki/Magnification

    As a practical matter, to find the focal length of your lens select a very distant luminous object, like the sun, and measure the distance from your lens to the image In this case the image will be the smallest spot that you can cause to form.
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  5. #4 Simple way to test magnification. 
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    Here is a simplistic way to measure the magnifying power of a magnifying glass: just draw a 1" line on a piece of paper. Then take a ruler, set it on top of the magnifying glass, hold both over the line and see how long it is, holding the glass in a way that makes the line as long as possible but still in focus. If it is now 3" long, there is 3x magnification; if it is 5" long, there is 5x magnification, etc. Thus it will be found that most magnifying glasses made in China are not at all what they claim to be. The 5x and 10x ones are often no more that 1.5x, 2x, or 3x. This idea of how to measure magnification seems to be verified by this professional web site's comments:

    Magnification

    Magnification is the process of enlarging an object in visual size, normally through an optical lens. It is the ratio between the apparent size and the true size of the viewed object behind the lens. If an object behind the lens appears ten times larger than its true size, and the object is in focus (i.e. at the proper focal length), the magnification is 10x. (Magnifying Glass Facts and FAQs )
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