 Measuring magnification - Printable Version +- Eyesight Improvement Forum (https://www.iblindness.org/forum) +-- Forum: General Discussion (https://www.iblindness.org/forum/forumdisplay.php?fid=4) +--- Forum: Complementary Methods (https://www.iblindness.org/forum/forumdisplay.php?fid=7) +--- Thread: Measuring magnification (/showthread.php?tid=1035) Measuring magnification - hellogreen - 12-08-2008 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. Re: Measuring magnification - otis - 12-09-2008 Dear Green, Subject: The Power of a lens. What you show here are "plus" lenses. The best term to use is "Diopters" to describe them. The "power" is calculated once you know the diopter value of the lens. If you wish to personally verify the "diopter power" of the lens -- do this. Take the lens outside in sun light. Hold the lens above a paper. Move the lens up or down until the Sun is focused on the paper (smallest image). Measure the distance between paper an lens. For example If the image forms at 20 inches, the power in diopters is 40/20 or 2 diopters. In cm this would be 50 cm, and the calculation would be 1/0.5 = 2 diopters. If the image formed at 1 meter (a weak lens), then it would be 1 / 1 = 1 diopter. The lenses you presented would be in this range. Best, Otis