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Magnifying glasses typically have low magnifying power: 2×–6×, with the lower-power types being much more common. At higher magnifications, the image quality of a simple magnifying glass becomes poor due to optical aberrations, particularly spherical aberration. When more magnification or a better image is required, other types of hand ...
By convention, for magnifying glasses and optical microscopes, where the size of the object is a linear dimension and the apparent size is an angle, the magnification is the ratio between the apparent (angular) size as seen in the eyepiece and the angular size of the object when placed at the conventional closest distance of distinct vision: 25 ...
The MNREAD acuity chart or Minnesota low vision reading chart is a text based chart used to measure near visual acuity in people with normal or low vision. [1] It can also be used to measure maximum reading speed, critical print size and the reading accessibility index of a person. [2] Digital and printed types of charts are available. [3]
As the user moves the pointer or cursor the screen magnifier should track with it and show the new enlarged portion. If this tracking is jerky or flickers it is likely to disturb the user. Also, the pointer or cursor may not be the content of interest: for example, if the user presses a keyboard shortcuts that opens a menu, the magnified ...
A Coddington magnifier is a magnifying glass consisting of a single very thick lens with a central deep groove diaphragm at the equator, thus limiting the rays to those close to the axis, which minimizes spherical aberration. This allows for greater magnification than a conventional magnifying glass, typically 10× up to 20×. Most single lens ...
Higher-quality optical-grade glass materials exist (e.g. Borosilicate crown glasses such as BK7 ( n d = 1.51680 , V d = 64.17 , D = 2.51 g/cm³ ), which is commonly used in telescopes and binoculars, and fluorite crown glasses such as the best optical quality low dispersion glass currently in production, N-FK58 made by the German company Schott ...
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